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Journal of Materials Processing Technology168(2005)262–269Process optimisation for a squeeze cast magnesium alloy metalmatrix compositeM.S.Yong a,∗,A.J.Clegg ba Singapore Institute of Manufacturing Technology,71Nanyang Drive,Singapore638075,Singaporeb Wolfson School of Mechanical and Manufacturing Engineering,Loughborough University,Loughborough,Leicestershire LE113TU,UKReceived5January2004;received in revised form5January2004;accepted27January2005AbstractThe paper reports the inﬂuence of process variables on a zirconium-free(RZ5DF)magnesium alloy metal matrix composite(MMC) containing14vol.%Safﬁlﬁbres.The squeeze casting process was used to produce the composites and the process variables evaluated were applied pressure,from0.1MPa to120MPa,and preform temperature from250◦C to750◦C.The principalﬁndings from this research were that a minimum applied pressure of60MPa is necessary to eliminate porosity and that applied pressures greater than100MPa causeﬁbre clustering and breakage.The optimum applied pressure was established to be80MPa.It was also established that to ensure successful preform inﬁltration a preform temperature of600◦C or above was necessary.For the optimum combination of a preform preheat temperature of600◦C and an applied pressure of80MPa,an UTS of259MPa was obtained for the composite.This represented an increase of30%compared to the UTS for the squeeze cast base alloy.©2005Elsevier B.V.All rights reserved.Keywords:Magnesium alloys;Squeeze casting;Metal matrix composites;Mechanical properties1.IntroductionMetal matrix composite(MMC)components can be man-ufactured by several methods.The metal casting route is espe-cially attractive in terms of its ability to produce complex near net shapes.However,castings produced by conventional cast-ing processes may contain gas and/or shrinkage porosity.The tendency for porosity formation will be exacerbated whenﬁ-bres are introduced because they tend to restrict theﬂow of molten metal and cause even greater gas entrapment within the casting.It is pointless to useﬁbres to reinforce a casting if defects are present,since the addition ofﬁbres will not com-pensate for poor metallurgical integrity.In order to fulﬁl the potential ofﬁbre reinforcement and produce pore free cast-ings the squeeze casting process can be selected.The unique feature of this process is that metal is pressurised throughout solidiﬁcation.This prevents the formation of gas and shrink-age porosity and produces a metallurgically sound casting.∗Corresponding author.E-mail address:msyong@.sg(M.S.Yong).Selection of this process is also based on its suitability for mass production,ease of fabrication and its consistency in producing high quality composite parts.With the development of MMCs,magnesium alloys can better meet the various demands of diverse applications.The addition of reinforcement to magnesium alloy produces su-perior mechanical properties[1–3]and good thermal stability [4,5].Of the various composite types,the discontinuous and randomly orientedﬁbre-reinforced composites provide the best“value to strength ratio”.Despite the potential advantage of using magnesium MMC for lightweight and high strength applications,little is known about the inﬂuence of squeeze inﬁltration parame-ters.Key parameters,such as applied pressure and preform temperature must be optimised,especially for the squeeze inﬁltration of a magnesium–zinc MMC.These process pa-rameters were researched and the results are presented in this paper.However,it wasﬁrst necessary to select appropriate ﬁbres and binders since their selection is fundamental to the success of the MMC.The main criterion determining the se-lection ofﬁbre type is compatibility with the matrix.Two0924-0136/$–see front matter©2005Elsevier B.V.All rights reserved. doi:10.1016/j.jmatprotec.2005.01.012M.S.Yong,A.J.Clegg/Journal of Materials Processing Technology168(2005)262–269263ﬁbre types that are known to be compatible with magnesium are Safﬁl and carbon[6].Silica and alumina-based binders are widely used in preform production,mainly due to their high temperature properties[7].However,there are concerns about chemical reactions between magnesium alloys and sil-ica[8].To ensure full inﬁltration of liquid metal into theﬁbre pre-form,researchers[9–11]have emphasised the importance of preheating the preforms.However,there has been lit-tle research to determine optimum preform temperature for magnesium alloys and that reported has focused on AZ91 (magnesium–aluminium)alloy.The wetting capability of these alloys is different,for instance the wetting and the in-terfacial reaction between Al2O3reinforcement and cerium, lanthanum(both rare earth elements)or magnesium is far better in comparison to aluminium.Most work on applied pressure has focused on aluminium alloys and their composites.However,Ha[12]and Chadwick [13]investigated the inﬂuence of applied pressure on the short freezing range Mg–Al family of alloys.The effect on solid-iﬁcation will inevitably be different for long freezing range alloys,such as the Mg–Zn family alloys that are the focus of this research.The difference in solidiﬁcation morphology will be signiﬁcant when inﬁltrating the melt into a porousﬁ-bre preform.Long freezing range alloys retain a liquid phase over a longer period during inﬁltration and this may promote better inﬁltration,reduce voids and consequently improve the soundness of the composite.2.Experimental methodologyA zirconium-free magnesium–4.2%zinc–1%-rare earths alloy,designated RZ5DF,was used for this research.Several ﬁbre preform materials,proportions and binder systems,were evaluated to determine their compatibility with the magne-sium alloys and the mechanical properties that they delivered to the composite[14].This preliminary research established that a compopsite based on a silica-bonded,14vol.%Safﬁl ﬁbre preform delivered the best characteristics in terms of ease of production and maximum‘value to strength ratio’.The effect of applied pressure,between0.1MPa and 120MPa,on the RZ5DF-14vol.%Safﬁlﬁbre composite was ﬁrst evaluated.The maximum permissible applied pressure was limited by both the capability of the squeeze casting press and die design.The metal pouring temperature was main-tained at750◦C,the die temperature at250◦C,the duration of applied pressure at25s,and delay before application of pressure at4s.These conditions replicated those employed for the base alloy that was reported previously[15].Following this,the inﬂuence of preform temperature was evaluated for a restricted range of applied pressures.Four preform temperatures were selected:250◦C(similar to the die temperature),400◦C(intermediate temperature),600◦C (at which temperature the RZ5DF alloy is a mixture of liquid and solid),and750◦C(at which temperature the RZ5DF alloy is in the fully molten state).These experiments were conducted at three applied pressures:60MPa,80MPa and 100MPa.The mechanical properties were evaluated using tensile and hardness tests.These tests were complemented by optical microscopy and,for the tensile fracture surfaces,SEM.2.1.Test castingThe test casting was a rectangular plate of126mm in length,75mm in width and16mm in depth.2.2.Melt processingThe alloy was melted in an electric resistance furnace us-ing a steel crucible,theﬂuxless method and an argon gas cover.The die was coated with boron nitride suspended in water to protect it from excessive wear.2.3.Tensile testingTensile tests were conducted on a50kN Mayes testing ma-chine using position control.Modiﬁed test specimens were machined according to BS18(1987)and magnesium Elek-tron Ltd RB4speciﬁcations[16].2.4.Hardness testingHardness was measured to determine and study the inﬂu-ence of reinforcement on the magnesium and the isotropy of ﬁbre distribution.The locations of hardness measurements are shown in Fig.1.Hardness measurements were conducted using the Rockwell B scale for both the alloys and com-posites.The preference for the Rockwell rather than Vick-ers hardness measurement was due to the larger indentation needed to ensure a more consistent measurement on the com-posite.The area of the Vickers hardness indentation is so small that,in some cases,the measurement could be taken from the hardﬁbre causing large variations in hardness val-ues.Fig.1.Locations of hardness measurements(each dot represents the position of a hardness measurement)taken in both‘Longitudinal’and‘Transverse’directions.264M.S.Yong,A.J.Clegg /Journal of Materials Processing Technology 168(2005)262–2692.5.MetallographyAn optical microscope and stereoscan 360electrom mi-croscope (SEM)were used to examine the microstructure of the MMC specimens.Metallographic samples were prepared using standard techniques and were etched using an acetic pi-cral solution.The electron microscope was equipped with a back-scatter detector and was used to characterise fracture surfaces from the tensile test specimens.2.6.Cell sizeThe cell size was established using the intersection method.Five areas were selected at random and 21mea-surements of cell size were taken for each area.The average value for the 105readings was determined.3.Results and observationsThe results are reported in the sequence in which the ex-periments were conducted.In the ﬁrst series of experiments,the effect of applied pressure was evaluated.In the second se-ries,the combined inﬂuences of applied pressure and preform preheat temperature were evaluated.3.1.Series 1experiments:the inﬂuence of applied pressure3.1.1.Tensile propertiesThe effect of applied pressure on UTS and ductility of squeeze cast,RZ5DF-14vol.%,Safﬁl ﬁbre composites is shown in Fig.2.It can be seen that the highest UTS value was obtained with an applied pressure of 80MPa.It would appear from the ﬁgure that a pressure in excess of 40MPa is essential to develop a signiﬁcant improvement in UTS but that levels above 80MPa have a detrimental effect.3.1.2.HardnessThe hardness values along the longitudinal and transverse directions of the composite castings produced atdifferentFig.2.The effects of squeeze inﬁltration applied pressure on the tensile properties of the RZ5DF matrix with 14vol.%fraction Safﬁlﬁbres.Fig.3.The average material hardness along the longitudinal and transverse direction of the squeeze inﬁltrated RZ5DF alloy with 14vol.%fraction Safﬁl ﬁbres,cast with constant pouring temperature of 750◦C and die temperature of 250◦C.applied pressures are shown graphically in Fig.3.Whilst the dominating inﬂuence on hardness is provided by the presence of the Safﬁl ﬁbres,the results show that the hardness at the two lowest levels of applied pressure (0.1MPa and 20MPa)is distinctly lower than that associated with applied pressure levels of 40MPa and above.3.1.3.MetallographyMetallography was conducted to examine the inﬂuence of applied pressure on the cast structure.Selected opti-cal microstructures are presented in Fig.4.The metal-lographic examination identiﬁed the presence of microp-orosity in those samples produced with applied pressures below 60MPa.The microporosity,as expected,occurred mainly at cell boundaries and was most easily conﬁrmed by adjusting the depth of ﬁeld.It also identiﬁed the ten-dency for ﬁbre clustering and fracture at applied pressures greater than 80MPa.The presence of fractured ﬁbres is demonstrated more clearly in the SEM micrographs shown in Fig.5.These micrographs show fractured ﬁbres in the plane transverse to that of load application during the tensile test.3.2.Series 2experiments:the inﬂuence of preform temperatureThe preliminary experiments showed that the optimum applied pressure was 80MPa.However,to ensure robustness in the experimentation,the effects of preform preheat temper-ature were evaluated for the optimum applied pressure and pressures of 60MPa and 100MPa.3.2.1.Tensile testsThe effects of preform temperature and applied pressure on UTS are summarised in Fig.6.The results show that a preform preheat temperature of 750◦C produced the most consistent UTS values across the range of applied pressuresM.S.Yong,A.J.Clegg/Journal of Materials Processing Technology168(2005)262–269265Fig.4.Optical microstructure of squeeze inﬁltrated RZ5DF-14vol.%fraction Safﬁlﬁbres produced under(i)atmospheric pressure,0.1MPa,applied pressure of(ii)20MPa,(iii)40MPa,(iv)60MPa,(v)80MPa,(vi)100MPa and(vii)120MPa.and that the maximum UTS of259MPa was obtained with a preform temperature of600◦C and an applied pressure of 80MPa.These results conﬁrm the status of80MPa as the optimum value of applied pressure.3.2.2.HardnessThe results of the hardness tests are shown in Fig.7.The greatest variation in hardness was demonstrated by the test casting produced with the lowest value of appliedpressure Fig.5.SEM micrograph of the fracture face of a squeeze inﬁltrated RZ5DF-14vol.%fraction Safﬁlﬁbres produced under applied pressure of(i)100MPa and (ii)120MPa.266M.S.Yong,A.J.Clegg/Journal of Materials Processing Technology168(2005)262–269Fig.6.The plot of UTS for RZ5DF-14vol.%Safﬁl MMC produced from various combinations of applied pressure and preform temperature. (60MPa)and preform temperature of400◦C.The range of variation was±8HRB compared to±6HRB observed for the other combinations of preform temperature and applied pressure.3.2.3.MetallographyMetallographic examination of the composite structures showed that more densely packedﬁbres occurred at the pre-form surface at the lowest preform temperature.This effect is illustrated in Fig.8.The sequence of microstructures show that preform deformation andﬁbre clustering were less evi-dent at higher preform temperatures.The SEM micrographs of tensile fracture surfaces,Fig.9,conﬁrm the clustering of ﬁbres and provide evidence ofﬁbre toﬁbre contact,for the preheat temperature of400◦C.This effect was not evident for the preheat temperature of600◦C.4.DiscussionTo achieve the successful inﬁltration of aﬁbre preform the liquid metal must penetrate the preform completely.Potential barriers to this are presented by:the density of the preform, which can be represented by the preform permeability[14]; Fig.7.The average material hardness along the longitudinal and transverse direction of the squeeze inﬁltrated RZ5DF alloy with14vol.%fraction Safﬁlﬁbres produced under different combinations of preform temperatures and appliedpressures.Fig.8.A micrograph taken at the preform inﬁltration region of a squeeze inﬁltrated specimen produced with a preform temperature of(i)750◦C,(ii)600◦C, (iii)400◦C and(iv)250◦C.M.S.Yong,A.J.Clegg/Journal of Materials Processing Technology168(2005)262–269267an insufﬁcient pressure head,necessary to displace the air and overcome resistances to metalﬂow;and/or a low pre-form temperature that promotes premature solidiﬁcation of the solid before complete inﬁltration.Increasing either the applied pressure or the preform pre-heat temperature,independently or in combination,may im-prove inﬁltration.However,there may be adverse conse-quences.Too high a level of applied pressure may physi-cally damage the preform through compression.This leads to compacted preforms that resist inﬁltration together withﬁ-bre clustering andﬁbre breakage that reduce theﬁbres’effec-tiveness for strengthening the matrix.Although researchers [11,17,18]have resorted to high preform temperatures to achieve inﬁltration,this too can have adverse effects.For example,an increased heat content in the system may retard solidiﬁcation.This in turn extends the time during which there is the opportunity for adverse interfacial reactions to occur between the alloy andﬁbres.Furthermore,an extended pe-riod of solidiﬁcation can promote the formation of larger cell sizes that in turn impair the mechanical properties.The inﬂuence of applied pressure is quite clearly demon-strated in Fig.2.Theﬁgure can be divided into three distinct regions:<60MPa,61–90MPa,>91MPa.Theﬁrst of these regions is associated with the presence of porosity and voids in the castings and this porosity is associated with low UTS values.As the applied pressure is increased the porosity is eliminated and the composite develops its optimum UTS of 259MPa at an applied pressure of80MPa.Thereafter,an increase in applied pressure producesﬁbre clustering and breakage leading to more initiation points for fracture and so the UTS declines.The tensile evidence is supported by evi-dence from hardness tests and metallography.The presence of porosity,revealed in Fig.4,adversely affects the hardness of the castings.Quite simply,low levels of applied pressure are not sufﬁcient to either suppress porosity formation or com-pletely inﬁltrate theﬁbre preform.It is interesting to note that the optimum applied pressure level of80MPa for the compos-ite is20MPa higher than that necessary to develop the highest level of strength in theﬁbre-free base alloy[15].Metallo-graphic examination revealed that preform deformation and ﬁbre clustering was less evident andﬁbres were less densely packed at the surfaces of the preforms preheated to600◦C or 750◦C(see Fig.8)when compared with400◦C and250◦C.It was found that the highest preform temperature(750◦C) produced the most consistent UTS values over the range of applied pressures considered.This preform temperature is above the liquidus temperature of the alloy.It would,there-fore,be expected that inﬁltration of the preform would not be impeded by the early onset of solidiﬁcation of the alloy on theﬁbre preforms.The preform temperature of600◦C pro-duced a higher variation in UTS than was observed for the 750◦C preform preheat temperature.However,the highest value of UTS of all the experiments was produced with this preheat temperature in combination with an applied pressure of80MPa.A preform temperature of750◦C supported a wider range of applied pressure because,even at the lowest level of 60MPa,there was a minimal resistance to inﬁltration.It was also noted that there was less variation inﬁbre distri-bution.An even distribution ofﬁbres was also evident in the specimens produced at a preheat temperature of600◦C, see Fig.9.This temperature is33◦C below the alloy’s liq-uidus temperature.Although inﬁltration was not a problem, it can be postulated that solidiﬁcation would occur quite quickly under these conditions.This postulation is supported by microstructural evidence and cell size measurements,see Fig.8,that show a smaller cell size,associated with better UTS,in the samples produced with a preform temperature of 600◦C.With preheat temperatures of400◦C and,especially, 250◦C the UTS values are generally poor and there is clear evidence of ineffective inﬁltration.The microstructural evi-dence clearly shows that preform deformation,ﬁbre cluster-ing andﬁbre breakage is evident to varying degrees.However, such effects were not uniform and produced inconsistent ef-fects.For example,for the combination of400◦C and60MPa applied pressure,microstructural evaluation,see Fig.10,re-vealed a high concentration ofﬁbres in the centre of the inﬁl-trated preform.This effect was caused by two factors.Firstly, the low preform preheat temperature promoted rapid solid-iﬁcation of the alloy prior to the application of pressure at both the preform surface and at locations near to the die wall. Secondly,the low applied pressure resulted in irregular and curtailed inﬁltration.In consequence,the applied pressure compacts rather than inﬁltrates the preform.This produces in-ﬁltrated regions that have a higher concentration ofﬁbresand Fig.9.SEM micrograph of the fracture face of a squeeze inﬁltrated RZ5DF-14vol.%Safﬁl MMC produced with(i)400◦C and(ii)600◦C preform temperature.268M.S.Yong,A.J.Clegg /Journal of Materials Processing Technology 168(2005)262–269Fig.10.Microstructure showing different parts of the squeeze inﬁltrated RZ5DF-14vol.%fraction Safﬁl specimen produced with a preform temperature of 400◦C and applied pressure of 60MPa.The sequence is (i)top,(ii)centre and (iii)bottom portion of the fabricated composite.this can produce higher values of UTS,see Fig.10.However,the effect is inconsistent and therefore undesirable.Hardness measurements also conﬁrmed the inconsistency.For exam-ple,the specimen produced with 60MPa and 400◦C preheat demonstrated the greatest variation in hardness,see Fig.7,and this was attributable to the central clustering of ﬁbres.Ex-amination of the fracture surface of the specimen produced with a preform temperature of 400◦C and an applied pres-sure of 80MPa clearly shows the ﬁbres in contact with one another,see Fig.9.4.1.The inﬂuence of zincAlloying magnesium with 4.2%of the lower melting point metal zinc produces a binary alloy that has a long freezing range.Experimentation [16]determined the values of the liquidus and solidus of the RZ5DF alloy to be 633◦C and 474◦C,respectively,a freezing range of 159◦C.Although long freezing range alloys are the most prone to shrinkage porosity,this problem is overcome by squeeze casting.The long freezing range may in fact be beneﬁcial in the produc-tion of a composite since the extended period during which a liquid phase is present may promote inﬁltration.The pres-ence of zinc may also be signiﬁcant for the preform preheat temperature.The results show that the optimum UTS of 259MPa was obtained with a preform temperature of 600◦C,a tempera-ture just 33◦C below the alloy’s liquidus temperature.Cell size measurements revealed that specimens produced at this preheat temperature had a smaller average cell size,typically 30␮m,see Fig.8.For specimens produced with preheat tem-peratures of 750◦C,400◦C and 250◦C the average cell size was >50␮m.This variation can be explained by consider-ation of the nucleation and growth sequence in the various specimens.The high preform preheat temperature retards the rate of solidiﬁcation because time is necessary for the heat of the preform to be transferred through the alloy to the die.Nucleating cells have time to grow.Conversely,at low pre-heat temperatures of 400◦C and 250◦C,the alloy solidiﬁesquickly in contact with the relatively cold ﬁbres.The ﬁrst solid formed is rich in the primary phase and the remaining liquid becomes richer in the low melting point eutectic.Al-though primary phase still forms by nucleation and growth in the inter-ﬁbre regions,the number of cells formed is reduced and their size is larger.5.Conclusions1.The optimum applied pressure for the squeeze casting of RZ5DF-14vol.%Safﬁl ﬁbre composites was determined to be 80MPa.At applied pressures below 60MPa,micro-porosity was not suppressed.Conversely,a high applied pressure of 100MPa or above causes ﬁbre clustering and breakage and a concomitant reduction in UTS.2.The optimum preform preheat temperature was estab-lished to be 600◦C.At this temperature consistent ﬁbre in-ﬁltration was achieved and the optimum cell size of 30␮m was obtained in the matrix.3.The optimum combination of applied pressure and pre-form preheat temperature was determined to be 80MPa and 600◦C,respectively.For this combination,a UTS value of 259MPa was obtained.The composite delivered a 30%increase in UTS compared with that developed in the squeeze cast base alloy.AcknowledgementsDr.Yong gratefully acknowledges the receipt of an Over-seas Research Students Award and a Loughborough Univer-sity Research Studentship.References[1]K.Purazrang,P.Abachi,K.U.Kainer,Investigation of the mechan-ical behaviour of magnesium composites,Composites 25(4)(1994)296–302.M.S.Yong,A.J.Clegg/Journal of Materials Processing Technology168(2005)262–269269[2]K.Purazrang,P.Abachi,K.U.Kainer,Mechanical behaviour of mag-nesium alloy MMCs produced by squeeze casting and powder met-allurgical techniques,Compos.Eng.3(6)(1993)489–505.[3]O.Ottinger,G.Grau,R.Winter,R.F.Singer,The effect of alu-minium additions on the interfacial microstructure and mechanical properties of C/Mg composites,in:Proceedings of the10th Inter-national Conference on Composite Materials(ICCM10),vol.VI, Vancouver,Canada,August1995,pp.447–454.[4]A Materials Edge Report,Metal matrix composites in the automotiveindustry,Met.Bull.plc.,(1993)1–33.[5]W.Toaz,R.R.Bowles,D.L.Mancini,Squeeze casting compositecomponents for diesel engines,Ind.Heat.54(3)(1987)17–19. [6]P.K.Rohatgi,Advances in cast mmc,Adv.Mater.Process137(2)(1990)39–44.[7]T.W.Clyne,P.J.Withers,An Introduction to Metal Matrix Compos-ites,Cambridge University Press,Cambridge,1993.[8]B.Inem,G.Pollard,Interface structure and fractography of amagnesium-alloy metal matrix composite reinforced with SiC parti-cles,J.Mater.Sci.28(1993)4427–4434.[9]H.Fukunaga,K.Goda,Fabrication ofﬁber reinforced metal bysqueeze casting,Bull.JSME27(228)(1984)1245–1250.[10]H.Fukunaga,Processing aspects of squeeze casting for shortﬁ-bre reinforced metal matrix composite castings,Adv.Mater.Manuf.Process3(4)(1988)669–687.[11]J.Kiehn,W.Riehemann,K.U.Kainer,P.V ostry,I.Stulikova,B.Smola,Annealing effects in shortﬁbre reinforced and unreinforcedMg–Ag–Nd–Zr alloy,in:Proceedings of the Third International Magnesium Conference,Manchester,UK,April,1996,pp.663–676.[12]T.U.Ha,Squeeze casting of magnesium-based alloys and their metalmatrix composites,Ph.D.Thesis,University of Southampton(1988).[13]G.A.Chadwick,Squeeze casting of magnesium alloys andmagnesium-based metal matrix composites,in:Proceedings of Mag-nesium Technology,London,The Institute of Metals,November 1986,pp.75–82.[14]M.S.Yong,R.I.Temple,A.J.Clegg,Inﬂuence ofﬁbre preform per-meability on inﬁltration of magnesium–zinc base alloys,in:Pro-ceedings of Magnesium Alloys and their Applications,Wolfsburg, Germany,18–20November,2003,pp.348–353.[15]M.S.Yong,A.J.Clegg,Process optimisation for a squeeze cast mag-nesium alloy,J.Mater.Process.Technol.145(January(1))(2004) 134–141.[16]M.S.Yong,Process optimisation of squeeze cast magnesium–zinc–rare earth alloys and shortﬁbre composites,Ph.D Thesis, Loughborough University,1999.[17]S.Kamado,Y.Kojima,Microstructure and tensile properties ofMg–Zn based alloy composite reinforced with Al2O3shortﬁbre and9Al2O3·2B2O3whisker,p.Mater6(3)(1997) 159–167.[18]J.H.Hsieh,C.G.Chao,Effect of magnesium on mechanical prop-erties of Al2O3/Al–Zn–Mg–Cu metal matrix composites formed by squeeze casting,Mater.Sci.Eng.A.214(1996)133–138.。

CoCrFeNi_系高熵合金研究进展

精密成形工程第15卷第8期孟爽，国栋，赵冬凤，余青，林毛毛（天津职业技术师范大学机械工程学院，天津 300222）摘要：高熵合金具有独特的微观结构和特性，作为一种新型的高性能材料，逐渐获得了国内外研究人员的广泛关注。

高熵合金具备多元化的元素组成方式，不但没有形成传统概念中复杂的相结构，反而展现出了更优异的性能，在诸多领域均具有良好的应用前景。

在当前的高熵合金体系中，CoCrFeNi系研究最为广泛，其研究内容主要体现在通过添加不同元素或进行退火热处理对原合金体系改性进而获得优异性能的材料。

首先，结合CoCrFeNi体系对高熵合金的定义和性能特点进行了分析和总结；其次，从热力学和动力学角度论述了CoCrFeNi系高熵合金的结构预测、层错能计算及缺陷动力学分析；再次，总结了Al、Ti、Cu、Mn 和C元素对CoCrFeNi系高熵合金显微组织和力学性能的影响；最后，分析了当前的研究现状并进行了展望。

关键词：高熵合金；CoCrFeNi系；模拟计算；合金元素；力学性能DOI：10.3969/j.issn.1674-6457.2023.08.019中图分类号：TG139 文献标识码：A 文章编号：1674-6457(2023)08-0156-13Research Progress of CoCrFeNi High Entropy AlloyMENG Shuang, GUO Dong, ZHAO Dong-feng, YU Qing, LIN Mao-mao(Faculty of Mechanical Engineering, Tianjin University of Technology and Education, Tianjin 300222, China)ABSTRACT: As a new high performance material, high entropy alloy has gradually got the attention of the world in recent years due to its distinctive microstructure and properties. The diversified element composition not only avoids the formation of complex phase structures in the traditional concept, but also exhibits superior performance to conventional alloys and has a wide range of potential applications. The CoCrFeNi system is now the mostly studied high entropy alloy system, which is mostly seen in the modification of the original alloy system through the addition of other elements and annealing treatment to produce supe-rior material properties. The definition and characteristics of a high entropy alloy combined with the CoCrFeNi system were firstly examined and summarized. Then, the structure prediction, calculation of layer fault energy and defect dynamics analysis of CoCrFeNi high entropy alloy were discussed from the perspective of thermodynamics and dynamics. Next, the effect of Al, Ti, Cu, Mn and C elements on the microstructure and mechanical properties of CoCrFeNi high entropy alloy was summarized. Fi-收稿日期：2023-04-21Received：2023-04-21基金项目：国家自然科学基金（52074193）；天津市自然科学基金科技计划重点项目（22JCZDJC00770）；天津市教委科研计划重点项目（2022ZD022）Fund：National Natural Science Foundation of China(52074193); Key Project of Tianjin Natural Science Foundation Science and Technology Program(22JCZDJC00770); Key Projects of the Tianjin Education Commission's Research Program(2022ZD022)作者简介：孟爽（1995—），女，硕士生，主要研究方向为高熵合金。

高导热低膨胀石墨

第51卷第11期2020年11月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.51No.11Nov.2020高导热低膨胀石墨/Cu-Zr 复合材料组织与性能陈存广1,2，崔倩月1，余程巍3，郝俊杰1,2，郭志猛1,2(1.北京科技大学新材料技术研究院，北京，100083；2.南方海洋科学与工程广东省实验室(珠海)，广东珠海，519000；3.北京天宜上佳高新材料股份有限公司，北京，102206)摘要：为解决导热鳞片石墨/Cu 复合材料中石墨取向及Cu-C 界面结合弱的难题，将Zr 元素引入铜基体中作为碳化物形成元素，以优化Cu-C 界面，并采用流延法和热压烧结工艺协同制备高取向石墨/Cu 复合材料。

研究结果表明：流延法是使鳞片石墨在基体中获得高排列取向度的有效手段；Cu-C 界面处形成ZrC ，界面结合更加紧密；复合材料热导率随Zr 加入量的增加先增大后减小，Zr 质量分数为0.5%时达到最大值604W/(m·K)，与纯Cu 相比，热导率提高52%；复合材料在Z 方向出现负膨胀现象，随着Zr 质量分数的增加，XY 平面热膨胀系数不断降低，Z 方向的热膨胀系数逐渐接近半导体的热膨胀系数；当Zr 质量分数增加到2.0%，复合材料的抗弯强度相对于未加Zr 的复合材料提高了42%，鳞片石墨的层间剥离和脱落是导致复合材料发生断裂的主要原因。

关键词：铜基复合材料；鳞片石墨；锆；高取向；负膨胀中图分类号：TB333文献标志码：A开放科学(资源服务)标识码(OSID)文章编号：1672-7207（2020）11-3072-09Microstructure and properties of graphite/Cu-Zr composites with high thermal conductivity and low coefficient of thermal expansionCHEN Cunguang 1,2,CUI Qianyue 1,YU Chengwei 3,HAO Junjie 1,2,GUO Zhimeng 1,2(1.Institute for Advanced Materials and Technology,University of Science and Technology Beijing,Beijing 100083,China;2.Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519000,China;3.Beijing Tianyishangjia New Material Co.,Ltd,Beijing 102206,China)Abstract:To overcome the technical difficulties of graphite orientation and weak Cu-C interface bonding in flake graphite/Cu composites,Zr was introduced into the Cu matrix as carbide forming element,optimizing the combination of interface phase.The highly-oriented flake graphite/Cu composite was prepared by tape-casting and hot-pressing sintering.The results show that tape-casting is an effective method to obtain high alignment of the flake graphite in the matrix.ZrC is formed at the Cu-C interface,contributing to the tighter interface bonding.TheDOI:10.11817/j.issn.1672-7207.2020.11.008收稿日期：2020−08−17；修回日期：2020−09−09基金项目(Foundation item)：国家重点研发计划项目(2016YFB1101201)；中央高校基本科研业务费专项资金资助项目(FRF-GF-19-012AZ)(Project(2016YFB1101201)supported by the National Key Research and Development Program of China;Project (FRF-GF-19-012AZ)supported by the Fundamental Research Funds for the Central Universities)通信作者：陈存广，博士，讲师，从事有色金属粉末冶金技术研究；E-mail ：***************.cn第11期陈存广，等：高导热低膨胀石墨/Cu-Zr复合材料组织与性能thermal conductivity(TC)of the composite increases first and then decreases with the increase of the Zr content.The maximum value of the TC of the composite with0.5%Zr(mass fraction)is604W/(m·K),which is52% higher than that of pure Cu.The composite exhibits a negative expansion phenomenon in the Z direction.With the increase of Zr content,the coefficient of thermal expansion(CTE)in the XY direction continues to decrease,and the CTE in the Z direction gradually approaches that of semiconductor.The flexural strength of the composite with2.0%Zr(mass fraction)is increased by42%compared to the composite without Zr.The exfoliation betweengraphite layers is the main reason for the fracture of composites.Key words:Cu matrix composite;flake graphite;Zr;high alignment;negative expansion微电子产品朝着小型化、多功能、高集成的方向发展，要求电子元器件具有更大的功率密度。

高强钢焊接工艺及接头组织与性能研究

高强钢焊接工艺及接头组织与性能研究摘要高强钢具有高强度、高韧性的优点，被广泛用在液压支架、汽车车壳上。

本文从焊接工艺、焊接接头组织、力学性能等特点对国内外高强钢焊接方面的研究成果进行了综述，得出高强钢焊接接头各个区域的组织与性能不同，在不同焊接规范下相同区域的金相组织基本相似，熔合区因组织不均匀为最薄弱环节，指出防止高强钢热影响区的脆性破坏以及提高钢的韧性是今后高强钢焊接研究的重点。

关键词：高强钢，焊接工艺，组织，力学性能Study on Welding Process and Microstructure and Propertyof High Strength SteelAbstractHigh strength steel with high strength, high toughness advantages, are widely used in hydraulic support, car shell. From aspects of welding process, joint microstructure and mechanical properties of high strength steel welding, the research results of the high strength steel welding at home and abroad were summarized. It indicates that the microstructure and mechanical properties of high strength steel weld joints are different in different regions, while the metallographic structures of the same region are basically similar under different welding parameters, the fusion zone is the weakest area due to the inhomogeneous microstructure. It is pointed out that to prevent the heat affected zone ( HAZ ) from brittle failure and to improve the toughness of the HAZ are the focus of future research on high strength steel welding．Key words：High strength steel, Welding process, organization, Mechanical properties目录摘要 (I)Abstract (II)前言 (1)1. 高强钢的发展状况 (2)1.1 高强钢的生产与发展 (2)1.2 高强钢的性能与分类 (2)1.3 高强钢的应用前景 (5)2. 高强钢焊接研究现状 (6)2.1 激光焊接 (6)2.2 气体保护焊 (7)2.3 电阻点焊 (7)3. 高强钢焊接工艺 (8)4. 高强钢焊接接头组织与性能研究 (9)4.1 焊接接头组织分析 (9)4.2 焊接接头力学性能分析 (10)5. 结语 (10)参考文献 (11)前言高强钢作为21世纪新一代钢铁材料，具有高强度和良好的塑韧性等力学性能，为现代制造业开启了新的发展空间。

Microstructure and properties of in situ synthesized TiB2+WC reinforced composite coatings

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Interfacial microstructure and mechanical properties of

Interfacial microstructure and mechanical properties of aluminium –zinc-coated steel joints made by a modifiedmetal inert gas welding –brazing processH.T.Zhang a,⁎,J.C.Feng a ,P.He a ,H.Hackl baState Key Laboratory of Advanced Welding Production Technology,Harbin Institute of Technology,Harbin 150001,Heilongjiang Province,PR ChinabFronius.Internation GMBH,A4600Wels-Thalheim,AustriaReceived 10May 2006;accepted 4July 2006AbstractThe microstructure and properties of aluminium –zinc coated steel lap joints made by a modified metal inert gas CMT welding –brazing process was investigated.It was found that the nature and the thickness of the high-hardness intermetallic compound layer which formed at the interface between the steel and the weld metal during the welding process varied with the heat inputs.From the results of tensile tests,the welding process is shown to be capable of providing sound aluminium –zinc coated steel joints.©2006Elsevier Inc.All rights reserved.Keywords:Welding –brazing;Heat input;Intermetallic compound1.IntroductionIn order to reduce pollution and save energy,it is attractive to make car bodies lighter by introducing some aluminium parts as substitutes for the previous steel structures [1,2].Therefore,joining aluminium to steel has become a major problem,requiring resolution.Direct solid-state joining can be used to make these dissimilar metal joints by controlling the thickness of the interme-tallic compound layer that develops within a few micrometers of the joint interface [3–9].However,the shape and size of such solid-state joints are extremely restricted.Thus,the joining of aluminium to steel byfusion welding methods has been widely studied.As is well known,the joining of aluminium to steel by fusion welding is difficult because of the formation of brittle interface phases which can deteriorate the mechanical properties of the joints.However,Kreimeyer and Sepold [10]have shown that if the layer is less than 10μm thick,the joint will be mechanically sound.In addition,the authors also deem that the existence of a zinc coating increases the wettability of the Al to the steel substrate.As another approach,Achar et al.[11]reported that the thickness of the intermetallic compound layer formed during TIG arc welding of Al to steel is decreased by the use of an Al alloy filler metal containing Si.Murakami et al.[12]and Mathieu et al.[13]both point out that the temperature probably determines the thickness of the intermetallic compound layer of the joint and recom-mended the use of lower heat input to obtain a sound joint.Materials Characterization 58(2007)588–592⁎Corresponding author.Tel.:+8645186412974;fax:+8645186418146.E-mail address:hitzht@ (H.T.Zhang).1044-5803/$-see front matter ©2006Elsevier Inc.All rights reserved.doi:10.1016/j.matchar.2006.07.008The cold metal transfer process,identified here as CMT,is a modified metal inert gas welding process which invented by the Fronius Company.The principal innovation of this method is that the motions of the welding wire have been integrated into the welding process and into the overall control of the process.Every time the short circuit occurs,the digital process-control both interrupts the power supply and controls the re-traction of the wire.The wire retraction motion assists droplet detachment during the short circuit,thus greatlydecreasing the heat input during welding.In this study,we selected the CMT process to join aluminium to zinc-coated steel using a lap geometry. The main purpose of this effort was to reveal the rela-tionship between heat input and the microstructure of the joint.Hardness testing was also used to characterize the phases formed during the welding process.In ad-dition,the quality of the joints was assessed by tensile testing.2.ExperimentalDeep drawn sheets of hot-dip galvanized steel and sheets of pure Al1060with thickness of1mm were used in the welding experiments.An Al sheet was lapped over a Zn-coated steel sheet on the special clamping fixture, and the ending of the weld wire was aimed at the edge of the aluminium sheet,as shown in Fig.1.The MIG welding–brazing was carried out using the CMTwelding source with an expert system and1.2-mm-diameter Al–Si filler metal wire.Argon was used as the shielding gas at a flow rate of15L/min.The surface of the samples was cleaned by acetone before welding.Two sets of welding parameters of different heat inputs were selected,as shown in Table1.The heat input,J,is calculated using the equation:J=(60×UI)/v,where U is the mean welding voltage,I is the mean welding current and v is the welding speed.Typical transverse sections of the samples were observed using optical microscopy(OM)and scanning electron microscopy(SEM).The composition of the intermetallic compound layer at the interface between the steel and the weld metal was determined by energy dispersive X-ray spectroscopy(EDX).Hardness values were obtained using a microindentation hardness tester with a load of10g,and a load time of10s.In addition, the samples were cut in10mm widths,and transverse tensile tests(perpendicular to the welding direction) were used to measure the joint tensilestrength.Fig.1.Schematic plan of the welding process.Table1The welding parametersSamplenumberMeanweldingcurrent(A)Meanweldingvoltage(V)Wire feedrate(m/min)Weldingspeed(mm/min)Weldheatinput(J/cm)Sample A6611.8 3.9762613.2Sample B11013.3 5.4913961.5Fig.2.Front(upper)and back(lower)appearances of typical jointswith different heat inputs:(a)Sample A;(b)Sample B.589H.T.Zhang et al./Materials Characterization58(2007)588–5923.Results and discussion 3.1.Macro-and microstructuresThe appearance of the weld seams for different heat inputs are shown in Fig.2.For all welding cases,a smooth weld seam was made.The molten metal wetted the steel better when using lower heat input,i.e.,compare Sample A at lower heat input to Sample B.This may be related to the different degree of evapo-ration of the zinc coating at different heat inputs.While improving the heat input,the greater evaporation of zinc reduces the wettability of the molten metal on the steel.Fig.3shows a typical cross-section of the joints.Higher heat input (Sample B)resulted in a decrease in the contact angle between the steel and the weld metal.Meanwhile,a special zone with lighter colour at the toe of the weldments can be found (designated by white arrows in Fig.3).Optical micrographs shows that a visible intermetallic compound layer has formed be-tween the steel and weld metal during the welding process,Fig.4.The thickness of the intermetallic com-pound layer changes not only with the location within a given joint but also with the varying heat input between different joints.The thickness of the intermetallic compound layer in the center is greater than at the edge of the seam within one joint.For Sample A,the maximum thickness of the compound layer is about 10μm but is 40–50μm for Sample B.The microstructure of the intermetallic compound is shown in greater detail in the SEM micrographs inFig.5.At lower heat input (Sample A),the inter-metallic compound presents a serrated shape oriented toward the weld metal.When the heat input was increased (Sample B),the compound layer became much thicker and grew into the weld metal with tongue-like penetrations.Anisotropic diffusion is a possible explanation for this irregularity.The intermetallic compounds that form under these conditions generally have an orthorhombic structure (see below).Because of the high vacancy concentration along the c -axis of the orthorhombic structure,Al atoms can diffuse rapidly in this direction and cause rapid growth of the inter-metallic compound.EDX analysis was used to determine the phases of the intermetallic compound layer.The results show that the intermetallic compound layer of the joint made by lower heat input consists entirely of Fe 2Al 5.But when the heat input is increased,the intermetallic compound layer consists of two different phases,the FeAl 2phase near the steel surface and a FeAl 3phase which penetrates toward the weld metal.Thus it is clearthatFig.4.Optical microstructures of interface between steel and weld metal:(a)Sample A;(b)SampleB.Fig.3.Cross-section image at limit of penetration in the joint,showing change in contact angle with increased heat input.Arrows point to an intermetallic compound at the tip of the weld metal:(a)Sample A;(b)Sample B.590H.T.Zhang et al./Materials Characterization 58(2007)588–592the intermetallic compound layer that forms is closely related to the heat input during the welding process.With regard to the special zone designated by white arrows in Fig.3,dendritic-appearing structures can be distinguished on a high-magnification SEM micrograph (Fig.6).EDX analysis results show that such dendrite-shaped crystals of an Al-richα-solid solution containing residual zinc routinely formed at this location.3.2.Hardness measurementsHardness testing results also confirm the presence of a hard intermetallic compound layer.The hardness of the interface layer is much higher than that of the base metal and the weld metal and is found to vary for the corresponding intermetallic compound phases.For the high heat input weld(Sample B)the hardness is much higher,Fig.7.Fig.8.The location where the fracture occurred during tensile testing (designated by white arrows):(a)Sample A;(b)SampleB.Fig.7.Microindentation hardness test results of the joints made using different heatinputs.Fig.6.Dendrite crystal structure at the toe of the weldment(SampleB).Fig.5.SEM micrograph of interface between steel and weld metal:(a)Sample A;(b)Sample B.591H.T.Zhang et al./Materials Characterization58(2007)588–5923.3.Tensile test resultsThe tensile tests were performed to provide a qualitative measure of the joint strength and behavior. These results show that the bond strength is excellent, with the fractures occurring in the HAZ of the Al even when the thickness of the intermetallic compound layer was greater than40μm,Fig.8.From a general view-point,the thickness of the intermetallic compound layer should be controlled to less than10μm in order to obtain a sound joint.This implies that the joint made with higher heat input should have a lower intrinsic strength than the other because of the thicker brittle intermetallic compound layer.However,the intrinsic strength of the joints cannot be determined when the fracture occurs in the HAZ of the pure Al.Nevertheless, according to the thickness of the compound layer,we can presume that the intrinsic strength of the joints should be decreased when increasing the welding heat input.4.ConclusionsBased on the experimental results and discussions, conclusions are drawn as follows1)Dissimilar metal joining of Al to zinc-coated steelsheet without cracking is possible by means of a modified metal inert gas(CMT)welding–brazing process in a lap joint.2)Fe–Al intermetallic compound phases were formedat the interface between the steel and the weld metal.The thickness and the composition of the interme-tallic compound layer varied with weld heat input.3)Despite the formation of the intermetallic compoundphases,the interface between steel and weld metal is not the weakest location of the joints.Tensile tests of the joints caused fractured in the Al HAZ,even when the intermetallic compound layer thickness exceeded 40μm.AcknowledgementsThe authors wish to acknowledge the financial support provided by the National Natural Science Foundation under Grant No.50325517for this work. References[1]Schubert E,Klassen M,Zerner I,Walz C,Sepold G.Light weightstructures produced by laser beam joining for future applications in automobile and aerospace industry.J Mater Process Technol 2001;115:2.[2]Schubert E,Zernet I,Sepold ser beam joining of materialcombinations for automotive applications.Proc SPIE 1997;3097:212.[3]Oikawa H,Ohmiya S,Yoshimura T.Resistance spot welding ofsteel and aluminium sheet using insert metal sheet.Sci Technol Weld Join1999;2:80.[4]Czechowski M.Stress corrosion cracking of explosion weldedsteel–aluminum joints.Mater Corros2004;6:464.[5]Fukumoto S,Tsubakino H.Friction welding process of5052aluminium alloy to304stainless steel.Mater Sci Technol 1999;9:1080.[6]Ochi H,Ogawa K,Suga Y,Iwamoto T,Yamamoto Y.Frictionwelding of aluminum alloy and steel using insert metals.Keikinzoku Yosetsu1994;11:1.[7]Shinoda T,Miyahara K,Ogawa M,Endo S.Friction welding ofaluminium and plain low carbon steel.Weld Int(UK) 2001;6:438.[8]Uzun H,Donne CD.Friction stir welding of dissimilar Al6013-T4to X5CrNi18-10stainless steel.Mater Des2005;1:41. [9]Adler L,Billy M,Quentin G.Evaluation of friction-weldedaluminum-steel bonds using dispersive guided modes of a layered substrate.J Appl Phys2001;12:6072.[10]Kreimeyer M,Sepold ser steel joined aluminium-hybridstructures.Proceedings of ICALEO'02,Jacksonville,USA;2002.[11]Achar DRG,Ruge J,Sundaresan S.Joining aluminum to steel,with particular reference to welding(III).Aluminum1980;4:291.[12]Murakami T,Nakata K.Dissimilar metal joining of aluminum tosteel by MIG arc brazing using flux cored wire.ISIJ Int 2003;10:1596.[13]Mathieu A,Mattei S,Deschamps A.Temperature control in laserbrazing of a steel/aluminium assembly using thermographic measurements.NDT&E Int2006;39:272.592H.T.Zhang et al./Materials Characterization58(2007)588–592。

不锈钢碳钢复合板的焊接工艺及接头组织性能研究

中图分类号 TG 457.11 学科分类号 080503
论文编号 1028706 12-0052
硕士学位论文
不锈钢/碳钢复合板的焊接工艺及接头组织性能研究
研究生姓名学科、专业研究方向指导教师陈忱材料加工工程不锈钢复合板的焊接王少刚副教授
南京航空航天大学
研究生院材料科学与技术学院
作者签名：日期：
南京航空航天大学硕士学位论文
摘
要
金属复合板以其优良的综合性能被广泛地应用于石油化工、建筑、交通运输及日用品等许多领域中。但是由于其基层与覆层之间的化学成分及理化性能差异较大，在焊接过程中容易出现覆层焊缝被稀释、产生成分偏析或者出现其它焊接程对焊缝金属的稀释作用，将基层与覆层分开焊接在之间添加过渡层焊缝。因此，对接头过渡层焊缝的工艺控制是顺利实现金属复合板焊接的关键所在，以保证复合板接头的焊接质量，基于此，本文对 304L/SA516Gr70 奥氏体不锈钢复合板、 405/Q245R 铁素体不锈钢复合板这两种不锈钢/碳钢复合板的焊接工艺及焊接性进行研究。针对不锈钢复合板的焊接特点，文中分别采用钨极氩弧焊（GTAW）和焊条电弧焊（SMAW）两种焊接方法，并分别采用 Cr、Ni 元素含量较高的 ER309L 焊丝、ER316 焊丝、A302 焊条作为填充金属，选用 X 型和 X 型开槽两种坡口型式对不锈钢/碳钢复合板进行对接焊。通过对在不同工艺条件下所获接头进行力学性能测试、微观组织分析及耐蚀性能评价等，确定试验条件下的最佳焊接工艺及参数。力学性能测试结果表明，两种不锈钢/碳钢复合板接头的抗拉强度与其母材本身的抗拉强度相当，且均断在远离熔合线的母材处，完全能够满足实际工程结构对接头的强度要求。在 304L/SA516Gr70 接头中，采用 X 型开槽坡口、SMAW 焊获得接头 A2 的抗拉强度最高；而在 405/Q245R 接头中，采用 SMAW 焊获得接头 B2 的抗拉强度比 GTAW 焊获得接头 B1 的高。利用光学显微镜（OM）、扫描电镜（SEM）、透射电镜（TEM）及 X 射线衍射仪（XRD）对不锈钢/碳钢复合板接头的过渡层焊缝（WM）、覆层不锈钢与过渡层焊缝熔合区（WM-SS）及基层碳钢与过渡层焊缝熔合区（WM-CS）进行组织观察、成分分析及相结构分析。结果表明，接头过渡层焊缝的微观组织均为铁素体分布在奥氏体基体上。在 WM-CS 界面处，两种不锈钢复合板接头均存在不同程度的碳迁移现象，其中 304L/SA516Gr70 接头在 WM-CS 界面处还存在一个宽度为 30~50μm 凝固过渡层。对该界面进行元素线扫描及能谱分析，发现 Cr、Ni 等合金元素浓度在该区域呈梯度分布，但是并未发现合金元素偏聚现象及有害相析出。采用化学浸泡法及电化学测试方法评价接头过渡层焊缝的耐点蚀性能，结果表明，对于 304L/SA516Gr70 接头，采用 ER316L 焊丝的钨极氩弧焊接头 A4 的耐腐蚀性能最好；对于 405/Q245R 接头，采用焊条电弧焊获得接头 B2 的耐腐蚀性能要优于钨极氩弧焊接头 B1。综上所述，在本文中试验条件下，采用所选择的焊接工艺均可在一定程度上实现不锈钢/ 碳钢复合板的高质量焊接。关键词：不锈钢复合板，焊接工艺，过渡层，力学性能，微观组织，耐蚀性

冷铁 chill(中英文对照)

冷铁英文名称：chill1、简介产品名称：冷铁制造工艺：冲压，成形，锻造，车削，铸造或焊接其它名称：内外冷铁，插片冷铁，冷却钉，螺旋状内冷铁，马蹄钉和铸造钉冷铁由镀锡或涂敷防粘膜稀浆的低碳钢或线材加工而成，并且可以加工成各式各样的形状和尺寸。

无论是马蹄钉还是直杆钉都可以作为冷铁使用。

在铸造生产中，冷铁被用来控制收缩和获得定向凝固。

外冷铁放在模子中顶着铸件壁。

内冷铁被压进型芯，或模壁，这样它们的一大部分就可以伸进模穴，从而达到预期的效果。

1, IntroductionProduct Name: cold ironManufacturing process: stamping, forming, forging, machining, casting or weldingOther names: internal and external iron chill, insert the cold iron nail, cooling, helical internal chill casting, horseshoe nails and nailCold iron tin or coated by anti mucosal slurry of low carbon steel or wire processing, and can be processed into every kind of shape and size. Both nail or nail straight rod can be used as cold iron. In foundry production, cold iron is used to control the shrinkage and directional solidification. Cold iron on the top wall of mold casting. The cold iron is pressed into the core, or die wall, so one of their most can into the mold cavity, so as to achieve the desired effect.2分类为增加铸件局部冷却速度，在型腔内部及工作表面安放的金属块称为冷铁。

WC硬质合金堆焊材料界面组织结构和力学性能

ＷＣ硬质合金耐磨堆焊材料是由高硬度的ＷＣ硬质合金颗粒和具有一定强度、韧性的胎体金属组成．由于其具有优异的耐磨性和承受冲击能力，广泛地应用于石油钻井、井下作业中作为铣鞋和磨鞋等打捞工具承受磨损的工作面［１－－３】．
磨铣工具在铣削深层落物过程中，承受很高的压应力、剪应力和冲击载荷的作用，特别是硬质合金刀头在高温下受到急冷急热的温度变化，其服役条件相当复杂．磨铣工具的失效是一个复杂的综合过程，其失效形式不仅有磨损、高温氧化，还有硬质合金颗粒的碎化及颗粒的脱落．一般来讲，硬质合金颗粒的脱落与胎体金属的耐磨性、硬质合金与胎体金属的界面结构有关．因此，为了提高磨
如果界面结合脆弱（存在裂纹或剥离），在载荷的作用下，易导致硬质合金颗粒的脱落．因此，硬质合金与胎体
金属界面结合的好坏，直接影响堆焊层中硬质合金的力学
性能和使用寿命．一般来讲，硬质合金与胎体金属结合的界面可以分
为：突变型、扩散型和化合物型．界面间没有化学反应和元素扩散时，即形成突变界面；在界面附近相互反应形成化合物时，则得到化合物型界面；当二者之间存在一定的溶解度时，便形成扩散型界面．从界面结合强度看，突变型界面最差，化合物型界面最好．图３，４分别是２号焊条中硬质合金与胎体金属的界面形貌、成分分布，以及界面
１实验方法
实验用硬质合金颗粒为具有高硬度和良好抗弯强度的ＹＴ５３５型ＷＣ硬质合金，经机械方法破碎成粒度为１—６ｍｍ的颗粒．胎体金属采用Ｃｕ基钎料，在Ｃｕ－Ｚｎ合金中加入一定量的Ｎｉ，其高温力学性能和耐蚀性能都有提高．硬质合金和胎体金属的主要化学成分和力学性能见表１．
万方数据
１２８０
金属学报
１２８２
金属学报
３６卷
的Ｘ射线衍射图．由图３可见，界面结合良好，二者之间只存在元素的扩散，在界面附近相互掺杂，表明这种界面不是突变型．图４分析表明，界面没有新的物相产生，而是以固溶的形式结合．这种结合形式主要是由于焊条成形温度较低，硬质合金边缘的碳化物的分解和扩散量很小，硬质合金边缘硬度的下降较小，这对提高焊条的质量是有利的．

复合细化变质对再生ADC10铝合金组织性能的影响

138前沿技术L eading-edge technology复合细化变质对再生ADC10铝合金组织性能的影响付亚城1，董晓琼1，闫俊2，杨镇江3（１．佛山市辰辉金属科技有限公司，广东　佛山　５２８２００；２．佛山市南海创利有色金属制品有限公司，广东　佛山　５２８２２５；３．广东鸿邦金属铝业有限公司，广东　广州　５１１３４０）摘要：采用光学显微镜和拉力试验机，研究了复合细化变质对再生ＡＤＣ１０铝合金显微组织与力学性能的影响。

结果表明：通过复合细化变质使再生ＡＤＣ１０铝合金的α－Ａｌ晶粒从粗大的树枝状转变为细小均匀的等轴状，使共晶Ｓｉ相和富Ｆｅ相从粗大的针片状转变为细小的纤维状和颗粒状，可显著提高再生ＡＤＣ１０铝合金的力学性能。

与未细化变质相比，细化变质后再生ＡＤＣ１０铝合金的抗拉强度为２８９．２ＭＰａ，断后伸长率为７．８％，抗拉强度提高了１６．７％，断后伸长率提高了５２．９％。

关键词：再生铝合金；ＡＤＣ１０铝合金；晶粒细化剂；变质剂中图分类号：ＴＧ１４６．２文献标识码：Ａ文章编号：１００２－５０６５（２０２３）１６－０１３８－３Effect of Refining and Modification on Microstructure and Properties of Recycled ADC10 Aluminum AlloyFU Ya-cheng 1, DONG Xiao-qiong 1, YAN Jun 2, YANG Zhen-jiang 3（１．Ｆｏｓｈａｎ　Ｃｈｅｎｈｕｉ　Ｍｅｔａｌ　Ｔｅｃｈｎｏｌｏｇｙ　Ｃｏ．，　Ｌｔｄ．，　Ｆｏｓｈａｎ　Ｇｕａｎｇｄｏｎｇ　５２８２００；　２．Ｆｏｓｈａｎ　Ｎａｎｈａｉ　Ｃｈｏｎｇ　Ｌｅｅ　Ｎｏｎ－ｆｅｒｒｏｕｓ　Ｍｅｔａｌ　Ｐｒｏｄｕｃｔｓ　Ｃｏ．，　Ｌｔｄ．，　Ｆｏｓｈａｎ　Ｇｕａｎｇｄｏｎｇ　５２８２２５；　３．Ｇｕａｎｇｄｏｎｇ　Ｈｏｎｇｂａｎｇ　Ｍｅｔａｌ　Ａｌｕｍｉｎｕｍ　Ｃｏ．，　Ｌｔｄ．，　Ｇｕａｎｇｚｈｏｕ　Ｇｕａｎｇｄｏｎｇ　５１１３４０）Abstract:　Ｔｈｅ　ｅｆｆｅｃｔｓ　ｏｆ　ｒｅｆｉｎｉｎｇ　ａｎｄ　ｍｏｄｉｆｉｃａｔｉｏｎ　ｏｎ　ｔｈｅ　ｍｉｃｒｏｓｔｒｕｃｔｕｒｅ　ａｎｄ　ｍｅｃｈａｎｉｃａｌ　ｐｒｏｐｅｒｔｉｅｓ　ｏｆ　ｒｅｃｙｃｌｅｄ　ＡＤＣ１０　ａｌｕｍｉｎｕｍ　ａｌｌｏｙ　ｗｅｒｅ　ｓｔｕｄｉｅｄ　ｂｙ　ｍｅａｎｓ　ｏｆ　ｏｐｔｉｃａｌ　ｍｉｃｒｏｓｃｏｐｅ　ａｎｄ　ｔｅｎｓｉｌｅ　ｔｅｓｔｉｎｇ　ｍａｃｈｉｎｅ．　Ｔｈｅ　ｒｅｓｕｌｔｓ　ｓｈｏｗ　ｔｈａｔ　ｔｈｅ　ｍｅｃｈａｎｉｃａｌ　ｐｒｏｐｅｒｔｉｅｓ　ｏｆ　ｔｈｅ　ｒｅｃｙｃｌｅｄ　ＡＤＣ１０　ａｌｕｍｉｎｕｍ　ａｌｌｏｙ　ｃａｎ　ｂｅ　ｉｍｐｒｏｖｅｄ　ｓｉｇｎｉｆｉｃａｎｔｌｙ　ｂｙ　ａｄｄｉｎｇ　ｇｒａｉｎ　ｒｅｆｉｎｅｒ　ａｎｄ　ｍｏｄｉｆｉｅｒ．　Ｔｈｅ　ｔｅｎｓｉｌｅ　ｓｔｒｅｎｇｔｈ　ｏｆ　ｔｈｅ　ｒｅｃｙｃｌｅｄ　ＡＤＣ１０　ａｌｕｍｉｎｕｍ　ａｌｌｏｙ　ｗｉｔｈ　ｒｅｆｉｎｉｎｇ　ａｎｄ　ｍｏｄｉｆｉｃａｔｉｏｎ　ｉｓ　２８９．２　ＭＰａ，　ａｎｄ　ｔｈｅ　ｅｌｏｎｇａｔｉｏｎ　ａｆｔｅｒ　ｆｒａｃｔｕｒｅ　ｉｓ　７．８％．　Ｔｈｅ　ｔｅｎｓｉｌｅ　ｓｔｒｅｎｇｔｈ　ｉｓ　ｉｎｃｒｅａｓｅｄ　ｂｙ　１６．７％　ａｎｄ　ｔｈｅ　ｅｌｏｎｇａｔｉｏｎ　ｉｓ　ｉｎｃｒｅａｓｅｄ　ｂｙ　５２．９％　ｃｏｍｐａｒｅｄ　ｗｉｔｈ　ｔｈａｔ　ｏｆ　ｔｈｅ　ｒｅｃｙｃｌｅｄ　ＡＤＣ１０　ａｌｕｍｉｎｕｍ　ａｌｌｏｙ　ｗｉｔｈｏｕｔ　ｒｅｆｉｎｉｎｇ　ａｎｄ　ｍｏｄｉｆｉｃａｔｉｏｎ．Keywords: ｒｅｃｙｃｌｅｄ　ａｌｕｍｉｎｕｍ　ａｌｌｏｙ；　ＡＤＣ１０　ａｌｕｍｉｎｕｍ　ａｌｌｏｙ；　ｇｒａｉｎ　ｒｅｆｉｎｅｒ；　ｍｏｄｉｆｉｅｒ收稿日期：２０２３－０６作者简介：付亚城，男，生于１９８２年８月，江西进贤人，大学学历，高级工程师，研究方向：再生铝合金制备技术。

材料科学与工程专业英语第10章翻译

The word "ceramic" is derived from the Greek keramos, which means "potter's clay" or "pottery." Its origin is a Sanskrit term meaning "to burn." So the early Greeks used "keramous" when describing products obtained by heating clay-containing materials. The term has long included all products made from fired clay, for example, bricks, fireclay refractories, sanitaryware, and tableware.“陶瓷”这个词是来自希腊keramos，这意味着“陶土”或“陶”。

它的起源是梵文术语，意思是“燃烧”。

因此，早期的希腊人用“keramous”描述加热含粘土的物料获得的产品。

这个词早已包括所有陶土制成的产品，例如，砖，粘土质耐火材料，卫生洁具，餐具。

In 1822, refractory silica were first made. Although they contained no clay, the traditional ceramic process of shaping, drying, and firing was used to make them. So the term" ceramic," while retaining its original sense of a product made from clay, began to include other products made by the same manufacturing process. The field of ceramics (broader than the materials themselves) can be defined as the art and science of making and using solid articles that contain as their essential component a ceramic. This definition covers the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components, and the study of structure, composition, and properties.1822年，耐火材料二氧化硅被首次提出。

材料科学与工程专业英语第二版_翻译答案(匡少平),单元：1,2,4,5,7,8,9,10,11,13,16,19,22

Unit1：2.英译汉材料科学石器时代肉眼青铜器时代光学性质集成电路机械(力学)强度热导率1.材料科学指的是研究存于材料的结构和性能的相互关系。

相反，材料工程指的是，在基于材料结构和性能的相互关系的基础上，开发和设计预先设定好具备若干性能的材料。

2. 实际上，固体材料的所有重要性质可以概括分为六类：机械、电学、热学、磁学、光学和腐蚀降解性。

3. 除了结构和性质，材料科学和工程还有其他两个重要的组成部分：即加工和性能。

4. 工程师与科学家越熟悉材料的结构-性质之间的各种相互关系以及材料的加工技术，根据这些原则，他或她对材料的明智选择将越来越熟练和精确。

5. 只有在极少数情况下材料在具有最优或理想的综合性质。

因此，有必要对材料的性质进行平衡。

3. 汉译英Interdispline dielectric constantSolid materials heat capacityMechanical properties electro-magnetic radiationMaterials processing elasticity modulus1.直到最近，科学家才终于了解材料的结构要素与其特性之间的关系。

It was not until relatively recent times that scientists came to understand the relationship between the structural elements of materials and their properties . 2.材料工程学主要解决材料的制造问题和材料的应用问题。

Material engineering mainly solve the problems of materials processing and materials application.3.材料的加工过程不但决定了材料的结构，同时决定了材料的特征和性能。

英语推荐钢铁是怎样炼成的作文

英语推荐钢铁是怎样炼成的作文Steel is one of the most essential materials in the modern world, used in a vast array of applications from construction and infrastructure to transportation and consumer goods. The process of creating this versatile alloy, known as steel-making, is a fascinating and complex undertaking that has evolved over centuries. In this essay, we will explore the intricacies of how steel is made, delving into the various stages and technologies involved in transforming raw materials into the strong and durable metal we rely on daily.At the heart of steel production lies the blast furnace, a towering structure where the primary ingredients – iron ore, coal, and limestone – are combined and subjected to intense heat and pressure. This process, known as smelting, reduces the iron ore to its elemental form, allowing the impurities to be separated and removed. The resulting molten iron, often referred to as pig iron, is then transferred to a basic oxygen furnace or electric arc furnace, where further refining takes place.In the basic oxygen furnace, a lance is used to inject pure oxygeninto the molten pig iron, causing a rapid reaction that removes unwanted elements such as carbon, silicon, and phosphorus. This process, known as decarburization, helps to precisely control the final carbon content of the steel, a critical factor in determining its strength and other properties. The electric arc furnace, on the other hand, utilizes powerful electric currents to melt and refine scrap metal, which is then combined with pig iron or other raw materials to produce the desired steel composition.One of the key innovations in modern steel-making is the continuous casting process, which has revolutionized the industry. In this method, the molten steel is poured into a water-cooled copper mold, where it begins to solidify into a long, rectangular billet or slab. As the billet or slab is continuously withdrawn from the mold, it is further cooled and cut to the desired lengths, eliminating the need for traditional ingot casting and subsequent reheating and rolling.The continuous casting process not only improves efficiency and productivity but also allows for greater control over the steel's microstructure and properties. By carefully managing the cooling rates and other parameters, steel producers can tailor the material's characteristics to meet the specific requirements of various applications, such as increased strength, ductility, or corrosion resistance.Another critical step in steel production is the rolling process, where the cast billets or slabs are heated to high temperatures and then passed through a series of rolling mills. These powerful machines apply immense pressure to the steel, reducing its thickness and increasing its length, width, and overall uniformity. The rolling process can be further divided into hot rolling and cold rolling, each with its own unique advantages and applications.Hot rolling involves feeding the steel into the rolling mills at temperatures typically above 1,000 degrees Celsius, allowing the material to be more easily deformed and shaped. This process is often used for the production of structural steel, such as beams and plates, as well as various other products like sheets, bars, and rails. Cold rolling, on the other hand, is performed at lower temperatures, usually below the steel's recrystallization point. This method results in a smoother surface finish and improved mechanical properties, making it well-suited for the manufacture of automotive parts, appliances, and consumer electronics.Beyond the basic steel-making process, there are numerous specialized techniques and treatments that can be applied to further enhance the material's characteristics. Heat treatment, for instance, involves subjecting the steel to controlled heating and cooling cycles, which can significantly improve its strength, hardness, and ductility. Alloying, the addition of other elements like chromium, nickel, ormanganese, can also impart specific properties, such as increased corrosion resistance or improved hardenability.The versatility of steel is further demonstrated by the wide range of specialized steel products available on the market. From stainless steel, renowned for its exceptional corrosion resistance, to tool steel, prized for its hardness and wear resistance, the steel industry continues to innovate and develop new grades to meet the evolving needs of various industries.In recent years, the environmental impact of steel production has become an increasingly important consideration. The industry has made significant strides in reducing its carbon footprint, with the adoption of more efficient furnace technologies, the use of renewable energy sources, and the increased recycling of scrap steel. These efforts, combined with ongoing research and development, are helping to make steel production more sustainable and environmentally friendly.In conclusion, the process of how steel is made is a testament to the ingenuity and technological advancements of human civilization. From the initial smelting of iron ore to the final rolling and specialized treatments, the steel-making industry has evolved over centuries to become a vital component of the modern world. As we continue to rely on this versatile material for a wide range ofapplications, the importance of understanding and advancing the steel-making process cannot be overstated. The story of how steel is made is one of innovation, efficiency, and a relentless pursuit of excellence, shaping the very foundations of our built environment and the products we use every day.。

共晶点温度英语

共晶点温度英语Eutectic TemperatureThe concept of eutectic temperature is a fundamental principle in materials science and metallurgy, with wide-ranging applications in various industries. Eutectic temperature refers to the specific temperature at which a mixture of two or more substances undergoes a phase transformation, resulting in the formation of a solid mixture with unique properties.At the eutectic point, the liquid phase and the solid phase of a multi-component system coexist in equilibrium. This means that the liquid and solid phases have the same composition and Gibbs free energy, making the system the most stable at this particular temperature. The eutectic temperature is typically lower than the individual melting points of the constituent components, which is a key advantage in many practical applications.The importance of the eutectic temperature lies in its influence on the microstructure and properties of materials. When a multi-component system is cooled below its eutectic temperature, the solid phase that forms is a homogeneous mixture of the individualcomponents, known as a eutectic structure. This structure is often desirable due to its improved mechanical and thermal properties compared to other microstructures.One of the most well-known examples of a eutectic system is the lead-tin (Pb-Sn) alloy, commonly used in soldering applications. The Pb-Sn alloy has a eutectic composition of approximately 63% tin and 37% lead, with a eutectic temperature of 183°C (361°F). At this temperature, the liquid Pb-Sn alloy solidifies into a fine-grained, homogeneous microstructure, which provides excellent wetting and bonding characteristics for soldering.The determination of eutectic temperature is crucial in various industries, including metallurgy, ceramics, and food processing. In metallurgy, the eutectic temperature is essential for understanding the phase diagram of alloy systems, which is used to predict the microstructure and properties of materials during solidification and phase transformations. In the ceramics industry, the eutectic temperature is crucial for the development of advanced materials, such as composite ceramics and glazes, where the controlled formation of a eutectic phase can enhance the desired properties.In the food industry, the concept of eutectic temperature is relevant in the study of food freezing, where the formation of ice crystals and the concentration of solutes can influence the texture and quality offrozen foods. The eutectic temperature of a food system determines the onset of freezing and the behavior of the food during the freezing process, which is crucial for optimizing the storage and preservation of food products.The determination of eutectic temperature is typically carried out using thermal analysis techniques, such as differential scanning calorimetry (DSC) or differential thermal analysis (DTA). These methods measure the heat flow or temperature difference between a sample and a reference material as a function of temperature, allowing the identification of the eutectic point and other phase transitions.In addition to the practical applications, the study of eutectic temperature also has important implications in the field of materials science and thermodynamics. The understanding of eutectic phenomena contributes to the development of more efficient and sustainable materials processing techniques, as well as the optimization of material properties for specific applications.In conclusion, the concept of eutectic temperature is a fundamental principle in materials science and engineering, with far-reaching applications in various industries. The ability to accurately determine and manipulate the eutectic temperature of materials has been instrumental in the development of advanced materials, efficientmanufacturing processes, and improved product performance. As materials science continues to evolve, the understanding and application of eutectic temperature will remain a crucial aspect of scientific and technological progress.。

固化工艺英语

固化工艺英语Solidification ProcessThe solidification process is a critical step in the manufacturing of a wide range of products, from metals and plastics to ceramics and composites. This process involves the transformation of a material from a liquid or molten state to a solid state, and it plays a crucial role in determining the final properties and characteristics of the product. In this essay, we will explore the various aspects of the solidification process, including the underlying principles, the factors that influence it, and its applications in different industries.At its core, the solidification process is driven by the thermodynamic principle of phase change. When a material is cooled below its melting point, the atoms or molecules within the material begin to lose energy and become more closely packed, resulting in the transition from a liquid to a solid state. This phase change is accompanied by a release of latent heat, which is the energy that is stored within the material during the melting process.The rate at which a material solidifies is influenced by a variety of factors, including the cooling rate, the composition of the material,and the presence of impurities or additives. Rapid cooling, for example, can lead to the formation of smaller, more uniform grains within the solid material, while slower cooling can result in larger, more irregular grains. The composition of the material, on the other hand, can affect the solidification process by altering the melting point and the rate of heat transfer.One of the key factors that influence the solidification process is the nucleation and growth of solid crystals within the liquid. Nucleation is the initial formation of solid crystals, which occurs when the temperature of the liquid drops below its melting point. These initial crystals then serve as the foundation for the growth of larger, more stable crystals. The rate of nucleation and the size and distribution of the resulting crystals can have a significant impact on the final properties of the solidified material.The solidification process is particularly important in the production of metals, where it plays a crucial role in determining the microstructure and mechanical properties of the final product. In the casting of metals, for example, the solidification process determines the size and distribution of grains, as well as the presence of defects such as porosity and segregation. By carefully controlling the solidification process, manufacturers can optimize the properties of the metal, such as its strength, ductility, and corrosion resistance.Similar principles apply to the solidification of other materials, such as plastics and ceramics. In the production of plastic parts, the solidification process can affect the surface finish, dimensional accuracy, and mechanical properties of the final product. In the case of ceramics, the solidification process can influence the microstructure and the resulting properties, such as strength, hardness, and thermal conductivity.In addition to its importance in manufacturing, the solidification process is also a critical aspect of many natural phenomena, such as the formation of rocks and minerals, the freezing of water, and the solidification of magma. Understanding the principles of solidification has important implications for fields such as geology, climatology, and materials science.Overall, the solidification process is a complex and multifaceted topic that is essential to the production of a wide range of materials and products. By understanding the underlying principles and the factors that influence the solidification process, manufacturers and researchers can optimize the properties of their products and develop new and innovative materials that meet the demands of an ever-changing world.。

合金元素对激光熔覆高熵合金涂层硬度影响的研究进展

第16卷第5期精密成形工程影响的研究进展林添祥，冯美艳，练国富*，陈昌荣，兰如清（福建理工大学机械与汽车工程学院，福州 350118）摘要：激光熔覆技术采用高能量密度的激光作为工艺的能量来源，能够对工件表面进行改性和修复，显著地改善了基体的表面力学性能，从而有效地延长了产品的生命周期。

激光熔覆是制备高熵合金的典型工艺之一，采用该技术并且添加合适的合金元素可以制备具备卓越性能的高熵合金涂层。

为清晰地阐明加入元素后增强激光熔覆高熵合金涂层硬度的作用机制，首先综述了目前国内外在激光熔覆过程中加入常见元素所制备的高熵合金涂层硬度性能的研究现状，其中高熵合金有特殊的“4种效应”，对金属间化合物有促进作用，其内部微观结构一般为FCC、BCC或者HCP等固溶相，通常通过固溶强化、沉淀强化和分散强化来强化，并且激光熔覆法会使高熵合金涂层快速冷却，从而显著改善合金的力学性能。

其次，分析了金属与非金属两大类元素对激光熔覆制备高熵合金涂层硬度强化的机理，总结了金属元素与非金属元素的添加对高熵合金涂层硬度的影响规律。

最后，针对激光熔覆制备高熵合金涂层硬度性能的改进，总结出了有效的方法，并对其未来发展进行了展望。

研究结果揭示了激光熔覆高熵合金涂层硬度强化的理论基础，为该领域的进一步发展提供了理论依据。

关键词：激光熔覆；高熵合金；硬度；影响机理；金属元素；非金属元素DOI：10.3969/j.issn.1674-6457.2024.05.023中图分类号：TG146 文献标志码：A 文章编号：1674-6457(2024)05-0201-24Research Progress on the Effect of Alloying Elements on the Hardness of LaserCladded High Entropy Alloy CoatingsLIN Tianxiang, FENG Meiyan, LIAN Guofu*, CHEN Changrong, LAN Ruqing(School of Mechanical and Automotive Engineering, Fujian University of Technology, Fuzhou 350118, China)ABSTRACT: Laser cladding technology uses high energy density laser as the energy source of the process, which can modify and repair the surface of the workpiece, significantly improve the mechanical properties of the matrix surface, and effectively extend the life cycle of the product. Laser cladding is one of the typical processes for the preparation of high entropy alloys. By using this technology and adding appropriate alloying elements, high entropy alloy coatings with excellent properties can be prepared. In order to clearly clarify the mechanism of enhancing the hardness of laser cladded high entropy alloy coatings after收稿日期：2023-12-18Received：2023-12-18基金项目：福建省自然科学基金（2022J01920）Fund：Natural Science Foundation of Fujian Province (2022J01920)引文格式：林添祥, 冯美艳, 练国富, 等. 合金元素对激光熔覆高熵合金涂层硬度影响的研究进展[J]. 精密成形工程, 2024, 16(5): 201-224.LIN Tianxiang, FENG Meiyan, LIAN Guofu, et al. Research Progress on the Effect of Alloying Elements on the Hardness of Laser Cladded High Entropy Alloy Coatings[J]. Journal of Netshape Forming Engineering, 2024, 16(5): 201-224.*通信作者（Corresponding author）202精密成形工程 2024年5月addition of elements, the current research status of hardness properties of high entropy alloy coatings prepared by adding com-mon elements in laser cladding process in China and abroad is reviewed firstly. Among them, high entropy alloy has special "four effects", which can promote intermetallic compounds. Its internal microstructure is generally FCC, BCC or HCP solid so-lution phase. It is usually strengthened by solution strengthening, precipitation strengthening and dispersion strengthening, and the laser cladding method allows the high entropy alloy coating to cool rapidly, thus significantly improving the mechanical properties of the alloy. Secondly, the mechanism of metal and non-metal elements on the hardness strengthening of high entropy alloy coating prepared by laser cladding is analyzed, and the effect of addition of alloy elements on the hardness of high entropy alloy coating is summarized. Finally, in order to improve the hardness properties of high entropy alloy coating prepared by laser cladding, the effective method is summarized and its future development is prospected. The research results reveal the theoreti-cal fundamentals for strengthening the hardness of laser cladded high entropy alloy coatings, and provide a theoretical basis for the further development of this field.KEY WORDS: laser cladding; high entropy alloy; hardness; effect mechanism; metal elements; non-metal elements随着科技的不断进步，传统合金材料的应用已经不能完全满足应用需求，因此，近年来，合金材料已经成为全球学术界的研究焦点。

方钴矿的界面调控与热电性能

摘要方钴矿热电材料是综合性能较好的中温热电材料，由于具有较大的载流子迁移率和Seebeck系数，使其具备高ZT值的潜力，但由于晶格热导率较高，导致ZT值较低，本文主要通过高能球磨纳米化、引入石墨烯、液相压实构建小角晶界等界面调控方式，降低晶格热导率，从而提高热电性能。

采用XRD、SEM、TEM、激光热导仪、电导率/塞贝克系数测试系统等方法研究了不同界面调控方式对方钴矿组织结构和热电性能的影响规律，得到如下研究成果：针对退火La0.8Ti0.1Ga0.1Fe3CoSb12方钴矿，采用高能球磨结合放电等离子体烧结（SPS）制备纳米结构块体材料，与参比样品相比，退火球磨样品的电导率基本一致，但塞贝克系数增大，相应功率因子也较高。

退火球磨样品结构纳米化增强了对声子的散射作用，降低了晶格热导率，623K时晶格热导率达到最低为0.8Wm-1K-1，较参比样品降低了33%。

通过高能球磨实现结构的纳米化不仅改善了电性能，也有效地降低晶格热导率，进而提高了热电性能，退火球磨样品的热电优值在723K时从0.8提升到1.05。

采用PECVD法在p型退火La0.8Ti0.1Ga0.1Fe3CoSb12方钴矿粉体表面原位组装石墨烯，制备出p型方钴矿/石墨烯复合材料，发现石墨烯的引入对p型La0.8Ti0.1Ga0.1Fe3CoSb12方钴矿的电导率无明显影响，但塞贝克系数略有提高。

石墨烯的引入明显降低p型La0.8Ti0.1Ga0.1Fe3CoSb12方钴矿的晶格热导率，673K时具有最低值为0.9Wm-1K-1，较参比样品降低了25%。

石墨烯的引入对电性能稍有改善的同时，明显降低晶格热导率，使ZT值在723K时从0.8提高到1.00。

采用熔体旋甩结合液相压实法制备n型Ce x Co4Sb14.4（x=0.1、0.125、0.15、0.175、0.2）方钴矿，发现电导率随着填充量的增加而增大，Seebeck系数与电导率的变化趋势相反，填充量为x=0.15的样品具有最高的PF，约为45.7 Wcm-1K-2。

钨极氩弧焊与激光熔覆修复的K403_镍基高温合金导向器叶片组织与性能

2024 年第 44 卷航　空　材　料　学　报2024，Vol. 44第 1 期第 121 – 132 页JOURNAL OF AERONAUTICAL MATERIALS No.1 pp.121 – 132引用格式：张国会，秦仁耀，周标，等. 钨极氩弧焊与激光熔覆修复的K403镍基高温合金导向器叶片组织与性能[J]. 航空材料学报，2024，44(1)：121-132.ZHANG Guohui，QIN Renyao，ZHOU Biao，et al. Microstructure and properties of K403 nickel-base superalloy guide vane repaired by tungsten inert gas welding and laser cladding process[J]. Journal of Aeronautical Materials，2024，44(1)：121-132.钨极氩弧焊与激光熔覆修复的K403镍基高温合金导向器叶片组织与性能张国会1, 秦仁耀1*, 周标1, 赵梓钧1, 郭绍庆1, 黄帅1,王悦欣2, 敖斌2（1．中国航发北京航空材料研究院 3D打印研究与工程技术中心，北京 100095；2．中国航发贵州黎阳航空动力有限公司工程技术部/技术中心，贵阳 550014）摘要：K403镍基高温合金具有优异的室温和高温综合性能，广泛用于航空发动机涡轮叶片及导向器的制造。

针对涡轮叶片长期服役于复杂工况产生的裂纹缺陷等问题，本工作先对钨极氩弧（tungsten inert gas，TIG）焊和激光熔覆两种工艺修复后的组织与拉伸性能展开对比分析，而后使用激光熔覆工艺修复叶片，并进行无损检测。

利用OM、SEM观察微观组织、断口形貌，利用EDS进行相的成分分析。

结果表明：TIG焊修复工艺在修复界面区附近易产生微裂纹缺陷，主要碳化物相和低熔点共晶组织引起；激光熔覆工艺修复区域的晶粒与组织更加均匀，微裂纹缺陷更易得到控制；激光熔覆工艺修复的试样综合力学性能明显高于TIG焊修复工艺的试样，且激光熔覆工艺具有较好的工艺稳定性，TIG焊修复工艺的室温拉伸强度为K403母材强度的69.22%，激光熔覆修复工艺室温抗拉强度达到了母材的87.44%，断口形貌显示修复区域的室温拉伸断口呈现出混合断裂特征，高温拉伸断口呈现出沿晶断裂的特征。

混凝土孔结构的预测模型

International Journal of Concrete Structures and MaterialsVol.3, No.2, pp. 81~90, December, 2009DOI 10.4334/IJCSM.2009.3.2.081Predicting Model for Pore Structure of Concrete IncludingInterface Transition Zone between Aggregate and Cement PasteGi-Sun g Pan g,1) Sun g-Tae Chae,2) an d Sun g-Pil Chan g3)(Received September 8, 2008, Revised July 30, 2009, Accepted November 20, 2009)Abstract:This paper proposes a semi analytical model to describe the pore structure of concrete by a set of simple equations. The relationship between the porosity and the microstructure of concrete has been considered when constructing the analytical model. The microstructure includes the interface transition zone (ITZ) between aggregates and cement paste. The predicting model of porosity was developed with considering the ITZ for various mixing of mortar and concrete. The proposed model is validated by the rapid experimental programs. Although the proposed model is semi-analytical and relatively simple, this model could be reasonably utilized for the durability design and adapted for predicting the service life of concrete structures. Keywords:porosity, microstructure, interface transition zone, durability, service life.1. IntroductionIt has been established for many years in the research community that the presence of chloride ions is the most significant cause for the corrosion of reinforcing bars in concrete structures. A great deal of work has been done to characterize and prevent the ingress of these chlorides into concrete. It is known from research works that the microstructure of concrete is the key to understand chloride diffusivity of concrete. The modeling of concrete material should be conducted considering the microstructure in order to predict the realistic deterioration of structures. Chloride diffusivity is strongly affected by the pore size distribution and connectivity. There are different types of pores in concrete: the gel pores in the cement gel, the capillary pores between the solids in the cement gel and finally, the pores in the interface between the cement gel and the aggregate. In addition, there can be air voids and cracks.During recent decades, a number of models have been developed for describing concrete, cement paste and the interfacial zone between cement paste and aggregates. The aim of these models has varied ; Earlier models1 aimed principally at the understanding of the physical behavior, geometry and shape of the paste, ranging from nano scale to micro scale. On the contrary, later models2 are frequently of numerical nature aiming at calculating the time-dependent specific properties such as porosity and pore geometry, heat of hydration, strength, transport properties, or aiming at developing numerical models regarding long-term properties, such as durability.This paper proposes a semi analytical model to determine the porosity for the Ordinary Portland Cement. This model has been developed to use the diffusivity analysis of concrete. To this end, the relationship between the porosity and the microstructure of concrete has been established by mathematical equations. The microstructure includes the interface transition zone (ITZ) between aggregate and cement paste. The predicting model of porosity was developed with considering the various mixing of mortar and concrete. The model proposed in the present study has been validated by three types of experimental programs on cement paste, mortar and concrete. The analytical results are discussed and compared to the test results in order to validate the new model.2. Microstructure of concrete2.1 Composition of concreteAt the macroscopic level, concrete is made up of two main phases: aggregate and cement paste. The aggregate is fixed within the cement paste by bond between the particles of the aggregate. Concrete is usually composed of approximately 65%~75% with aggregate and 25%~35% with cement paste.It is obvious at the microscopic level that the two phases, aggregate and paste, are neither homogeneously distributed with respect to each other, nor are themselves homogenous.At the casting of the concrete, air voids are entrapped due to treatment or compression work, or entrained when frost-entraining agents are added. Such air voids are much larger (0.3~1mm) than the other pores in the paste, but are normally assigned to the paste phase. In the presence of aggregate, the structure in the vicinity of large aggregate particles is usually very different from1)KCI Member, Electric & Nuclear Power Division, Korea Insti-tute of Energy Technology Evaluation and Planning, Seoul 135-280, Korea. Email: gspang@ketep.re.kr.2)KCI Member, Korea Institute of Construction Materials, Seoul137-707, Korea.3)KCI Member, Dept. of Civil and Environmental System Engi-neering, University of Incheon, Incheon 402-749, Korea.Copyright ⓒ 2009, Korea Concrete Institute. All rights reserved,includ ing the making of copies without the written permission ofthe copyright proprietors.8182│International Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)that of the bulk paste. There is a third phase, the transition zone,which represents the interfacial region between the large aggregate particles and the cement paste. A schematic picture of the composition of concrete is shown in Fig. 1.2.2 Microstructure of cement pasteWhen cement and water are mixed, the cement reacts with the water to form a porous conglomerated mass of fine crystal-like gel particles constituting the cement gel, see Fig. 2. The main volume of the gel consists of calcium-silicate-hydrate (C-S-H) products in which calcium hydroxide (CH) is incorporated, and the gel volume grows as the hydration proceeds. Part of the original volume not occupied by gel consists of capillary pores, which are much coarser than gel pores. Y oung pastes have a inter-connected capillary-pore system but, as hydration proceeds, the hydration products grow into the capillary pores resulting in the reduction of the capillary pore volume.Photographs taken by an SEM microscope, one of the specimen tested in the present work are shown in Fig. 3 obtained from theprevious research.3The physical structure of the cement paste can be discerned to some extent there. The fluffy balls consist of hydrated C-S-H gels that have grown into the capillary pores. The internal porosity of the cement paste is high, as can be seen. The CH grows inside the C-S-H, or between the parts of it. It is limited in size by the space available.The older the cement paste becomes the denser and the more featureless the C-S-H gel appears. T obermorite and Jennit are natural minerals that resemble C-S-H gel. This has an extraordinarily high internal surface area as measured by water adsorption, in the range of 250 ~ 450m 2/g or 100 ~ 700m 2/g.4,52.3 Volume relationship of cement pasteA classification of the porosity of cement paste is given in T able 1.4Table 1 shows there is an enormous range of pore size distribution,from 10µm to less than 0.5nm in diameter. It is known that the pore size distributions are mainly affected by the w/c ratio and the degree of hydration. As can be seen in Table 1, porosity over the whole size range of pores has an influence on paste properties. Y et it is difficult to get an exact assessment of pore-size distributions because no one measurement encompasses the whole size range and because it is difficult to interpret experimental data. Thus,comparisons of porosity should be made with care.4Basic volume relationships between cement, cement gel, gel pores, capillary pores and water in cement paste are shown in Figs. 4 and 5. Figure 4 shows that the volume relationship in cement paste varies with increasing hydration. As shown in Fig. 5,increasing w/c ratio results in increasing capillary pore volume,but maintaining the constant level of gel pores.Fig. 2 Development of the struc ture of c ement paste ac c ording to Powers.1Fig. 3 SEM photograph.3Fig. 1 Sc hematic pic ture of the c omposition of c onc rete.International Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)│833. Analytical model of pore structure ofconcrete3.1 Porosity of cement pasteIn this study, the structure of the concrete is based on a structural model described in Fagerlund,6 which is based on the work ofPowers.1The model is described mathematically by a set of simple equations, for calculating the volume fraction of the ordinary Portland cement, hydration products (gel) and pores. Powers proposed certain empirically based equations, derived from experimental data. The equations do not distinguish between the various hydration states and different types of the hydration products, all are regardedas cement gel. Besides, a given increase in degree of hydration is assumed to create the same amount and structure of cement gel irrespectively of at what hydration state this additional hydration occurs.The total pore volume (V p )p of the cement paste is as shown in Fig. 6.(1)where (V p )p =total pore volume of the cement paste (m 3); W =content of water mixed (kg); W n =chemically bound water (kg);ρw =density of water (kg/m 3); and w/c =water to cement ratio.In the above model, it is assumed that the chemically bound water “decreases” in volume to 0.75 of the volume it had prior to hydration, and the water bound chemically in the hydration process is , where α=degree of hydration (−). The typical value of k is 0.23.For the following expression, the maximum possible degree of hydration, αmax equal to (w/c)/(w/c)*, must be substituted for a if w/c ≤w/c *. The typical value of w/c * is 0.38.The compact volume, i.e. the solid volume without any pores,of the cement paste (V 0)p is;(2)where (V 0)p =compact volume of the cement paste (m 3),ρc =density of the cement (kg/m 3)The total volume of the cement paste V p is the sum of the pore volume and the compact volume (3)The total porosity of the cement paste P p is (4)The ratio of the volume of hydration product to that of the cement from which it is formed may be calculated by dividing the former quantity by the volume of cement reacted per unit mass ofcement, which is α/ρc , giving . Therefore, theV p ()p W 0.75W n –ρw ---------------------------W 0.75k αC –ρw ------------------------------Cρw-----w/c 0.75k α–()===k αC ⋅⋅V o ()p C ρ---c 0.75W n ρw -----------------+C ρw -----ρwρc-----0.75k α+⎝⎠⎛⎞==V p V p ()p V 0()p +C ρw -----ρwρc-----w/c +⎝⎠⎛⎞==P p V p ()p V p------------w/c 0.75k α–ρw ρc-----w/c +------------------------------==1w/c ()*ρc /ρw +Table 1 Classific ations of the pore sizes in hydrated c ement.Type Diameter (nm)Description Role of waterPaste properties affectedCapillary pores 50~10,000Large capillariesBehaves as bulk waterStrength, permeability10~50Medium-sized capillaries Moderate surface tension forces generated Strength. permeability; shrinkage at high humidity Gel pores2.5~10Small (gel) capillaries Strong surface tension forces generated Shrinkage to 50% RH 0.5~2.5MicroporesStrongly adsorbed water; no menisci form Shrinkage, creep <~0.5Micropores “interlayer”Structural water involved in bondingShrinkage, creepFig. 4 Volume relationship of hydrated pastes by c hangingdegree of hydration.4Fig. 5 Volume relationship of hydrated pastes by c hanging w/cratios.4Fig. 6 Volume relationships among constituents of the hydratedpaste.84│International Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)volume of the cement gel is;(5)It is assumed that the cement gel formed during hydration has aporosity of 28%, therefore the volume of the gel pores (V gel )p is;(6)The gel porosity of the cement paste P gel is (7)The volume of the capillary pores (V cap )p in the cement paste is =(8)The capillary porosity P cap of the paste is(9)3.2 Interfacial zones between cement paste and aggregateThe structure of aggregate depends on the types of minerals in the aggregate and on its geological history which differ markedly from one location to another. In Korea, fractions of crushed granite and gneiss are normally used. Such aggregates are hard, tight and not easily dissolved. Although the porosity is low, only about 0~1%,the pores in these types of aggregate are quite coarse and are often so interconnected that the permeability and the diffusivity of for example, granite, are in parity with that of cement paste of a highw/c ratio.5,7Between the cement paste and the aggregate there is a thin,rather porous inter-facial zone (sometimes called the transition zone, tz), see Fig. 7. It becomes increasingly porous during hydration and normally has a larger content of CH-crystals than the bulk paste located farther from the aggregate does. This zone may also crack due to differences in modulus of elasticity and strength of aggregate and cement paste. Referring to the work of other researchers,Winslow et al.2 noted a region of approximately 50nm thickness which, has quite different properties than the rest of the bulk paste.Bourdette et al.8 estimated from the literature the transition zone (tz) to be 30µm thick. Using their models of hydration around the tz, they obtained results for porosity three times as high in tz as in the bulk paste, although it decreased with hydration age, whereas the porosity of the bulk paste remained relatively constant.3.3 Porosity and density of concreteFor mortar and concrete, additional porosity occurs in pore sizeslarger than the plain paste’s threshold diameter measured by mercury intrusion porosimetry (MIP).2 In Winslow et al., mortars with a w/c of 0.4 were made with aggregate of different ratios.The samples were hydrated in lime-saturated water for 28 days and were then oven dried at 105o C. The pore size distributions of the pastes were obtained by MIP . An average thickness of the paste surrounding each aggregate particle was calculated by dividing the volume of paste in the mixture by the surface area of the sand in the mixture. A computer program for random particle placement, percolation assessment and phase fraction estimation was developed. By executing the program for different number of aggregate particles, the volume fraction of aggregate required for interfacial zone percolation for a given aggregate size distribution and interfacial zone thickness was determined and compared to experimental results. An interfacial zone thickness of 15~20µm was found to be most consistent with results of the experiments.In this study, the volume of tz is calculated from the concept of equivalent radius of aggregate and thickness of tz. It is assumed that maximum thickness of tz is 30mm, which increases by degree of hydration. The equivalent radius of aggregate is calculated from the size distribution of sand and coarse aggregate as follows;(10)where r e =equivalent radius of aggregate, t TZ =thickness of tz,r i =radius of aggregate used and m i =mass ratio of aggregate, r i ,in this study, t TZ =30 (µm).In this study, the pore volume of aggregate is ignored. The volume of aggregate is (11)where β=G/CIt is assumed that the volume of tz is proportion to degree of hydration. The total volume of tz is calculated as follows;(12)V gel C αρc -------1w/c ()*ρc ρw -----+⎝⎠⎛⎞C αρw -------ρw ρc-----w/c ()*+⎝⎠⎛⎞==V gel ()p 0.28V gel 0.28αC ρw -------ρwρc-----w/c ()*+⎝⎠⎛⎞==P gel V gel ()p V p---------------0.28αρw ρc -----w/c ()*+⎝⎠⎛⎞/ρw ρc -----w/c ()+⎝⎠⎛⎞==V cap ()p V p ()p V gel ()p –=Cρw-----w /c 0.75k 0.28ρw ρc -----w/c ()*+⎝⎠⎛⎞+⎝⎠⎛⎞α–P capw /c 0.75k 0.28ρwρc-----w /c ()*+⎝⎠⎛⎞+α–ρwρc-----w /c +-----------------------------------------------------------------------------------=r e t TZ +()3r e ()3–r i t TZ +()3r i ()3–[]m i∑=V a G ρG ------C ρw -----ρw ρG ------β⎝⎠⎛⎞==V TZ 1t TZ r e ------+⎝⎠⎛⎞31–G ρG ------α1t TZ r e ------+⎝⎠⎛⎞31–C ρw -----ρw ρG ------β⎝⎠⎛⎞α==Fig. 7 Sc hematic representation of the transition zone.5International Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)│85where G =aggregate content, ρG =density of aggregate.The porosity of tz is three times as high as in the bulk cement paste,8the pore volume of tz can be calculated;(13)The total pore volume of the mortar or concrete is as shown in Fig. 8. The Equation (1) is modified since pore volume of tz and airs are included.(14)The total volume of the mortar or concrete is; (15)The total porosity of mortar or concrete is (16)It is assumed that the volume of gel pore is same as the cement past, so gel porosity of concrete is =(17)The pore volume of tz is included in the volume of the capillary pore in the mortar or concrete because pore size of tz belongs to capillary pore. The volume of capillary pore and porosity are; (18)The porosity of cement paste in mortar and concrete is; (19)V TZ ()p 3w/c 0.75k α–ρw ρc-----w/c +------------------------------1t TZ r e ------+⎝⎠⎛⎞31–C ρw -----ρw ρG ------β⎝⎠⎛⎞α=V c ()p V p ()p V TZ ()p V air ++Cρw-----w/c 0.75k α–()==3+w/c 0.75k α–ρwρc-----w/c +------------------------------1t TZ r e ------+⎝⎠⎛⎞31–C ρw -----ρw ρG ------β⎝⎠⎛⎞αV air +V c V a V p V TZ V air +++C ρw -----ρw ρG ------β⎝⎠⎛⎞C ρw -----ρw ρc -----w/c +⎝⎠⎛⎞+== 1t TZ r e ------+⎝⎠⎛⎞31–C ρw -----ρw ρG ------β⎝⎠⎛⎞αV air ++P c V c ()pV c------------=w/c 0.75k α–()3w/c 0.75k α–ρw ρc-----w/c +-----------------------------1t TZ r e ------+⎝⎠⎛⎞31–ρw ρG-----β⎝⎠⎛⎞αρw C -----V air++ρw ρc -----w/c +⎝⎠⎛⎞11t TZ r e ------+⎝⎠⎛⎞31–α+⎝⎠⎛⎞ρw ρG-----β⎝⎠⎛⎞ρw C -----V air++-------------------------------------------------------------------------------------------------------------------------------------------------P gel c,V gel ()p V c---------------=0.28αρwρc -----w/c ()*+⎝⎠⎛⎞ρw ρc -----w/c +⎝⎠⎛⎞11t TZ r e ------+⎝⎠⎛⎞31–α+⎝⎠⎛⎞ρw ρG ------β⎝⎠⎛⎞ρw C-----V air++----------------------------------------------------------------------------------------------------------------------P cap c ,V p ()p V gel ()p V TZ ()p+–V c------------------------------------------------------=w/c α0.75k 0.28ρwρc -----w/c ()*+⎝⎠⎛⎞+⎝⎠⎛⎞–= 3w/c 0.75k α–ρw ρc-----w/c +------------------------------1t TZ r e ------+⎝⎠⎛⎞31–ρw ρG------β⎝⎠⎛⎞α+ρw ρc -----w/c +⎝⎠⎛⎞11t TZ r e ------+⎝⎠⎛⎞31–α+⎝⎠⎛⎞ρw ρG------β⎝⎠⎛⎞ρwC -----V air++------------------------------------------------------------------------------------------------------------------------P ′gel c ,V gel ()pV c V a–---------------=0.28αρw ρc -----w/c ()*+⎝⎠⎛⎞ρw ρc -----w/c +⎝⎠⎛⎞1t TZ r e ------+⎝⎠⎛⎞31–αρw ρG------β⎝⎠⎛⎞ρw C -----V air++-------------------------------------------------------------------------------------------------------------=Fig. 8 Sc hematic volume frac tions of pores and solid materials.86│International Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)(20)4. Experiments4.1 Materials and mixture proportionsThe three types of experiments (cement paste, mortar, and concrete) were conducted for the evaluation of porosity. The materials used and mixture properties are summarized in Table 2,Tables 3 and 4. The Ordinary Portland Cement was used for all experiments and porosities are tested at various times, such as 1, 3,7, 14, 28 and 91days.The water-binder ratios of cement pastes are 0.3, 0.35, 0.4, 0.5,0.6 and 0.7 in cement paste. For evaluating the effects of aggregate,mortar were manufactured. The main variables are w/c (0.4, 0.5,0.55, 0.6 and 0.65) and the mass ratio of sand and cement (S/c =1,1.5 and 2). The maximum sizes of fine and coarse aggregate are 5mm, 13mm respectively and various w/c ratios (0.4, 0.5 and 0.6) are used.4.2 Test methodsMercury Intrusion Porosimetry (MIP) is a technique used tomeasure pore size distribution, and has an advantage in that it is able to span the measurement of pore sizes ranging from a few nanometres, to several hundred micrometers. As concrete has a distribution of pore sizes ranging from sub-nanometer to many millimeters, MIP has formed an important tool in the characterization of pore size distribution and total volume of porosity.The specimens are dried to remove all moisture from the pore structure. They are then placed into sealed “penetrometers” which are weighed both before and after being loaded with the specimen.The penetrometers are placed into the machine where they are evacuated and then filled with mercury. The pressurized testing then commences and the machine calculates and records how much mercury is being forced into the pore structure.The degree of hydration, α, is defined as the fraction of cement that has fully hydrated. For the present experiments, α was determined experimentally by comparing the amount of non-evaporable water in a sample to the amount needed for complete hydration. To determine the non-evaporable water content, four dried specimens from each paste group were subjected to ignitionat 800oC for 2h, cooled in vacuum desiccators at less than 20Pa for 1h, and then weighed. The water in the paste that was not removed by the drying process, W n , (also known as the non-evaporable water) is then estimated as shown in Eq. (21).(21)where, w 1 and w 2 are the weights of the dry specimen before and after ignition, respectively.The degree of hydration can then be calculated as shown in Eq.(22)(22)where (W n /C )* is the non-evaporable water corresponding to a completely hydrated paste. The typical value of it is 0.25.The total porosity of specimen is calculated by Eq. (23).(23)where, W 1, W 2, and W 3 are weight after 105oC oven dry, weight in water and weight in surface dry condition.4.3 MeasurementsThe results obtained from the instrument are;1)pore size distribution(macro/meso range of porosity spectrum)2)hysteresis curve, specific surface, bulk density 3)total porosity (%), particle size distributionThe non-evaporable water contents by degree of hydration, the measured results are summarized in Table 5. The porosities of capillary pore volume were obtained by MIP . The effects of water/cement ratios and sand contents on porosity are estimated by MIP .For various degree of hydration, porosities of specimens are measured and the results are summarized in Table 6.w/c α0.75k 0.28ρwρc -----w/c ()*+⎝⎠⎛⎞+⎝⎠⎛⎞–P ′cap c ,= 3w/c 0.75k α–ρw ρc-----w/c +------------------------------1t TZ r e ------+⎝⎠⎛⎞31–ρw ρG ------β⎝⎠⎛⎞α+ρw ρc -----w/c +⎝⎠⎛⎞1t TZ r e ------+⎝⎠⎛⎞31–αρw ρG------β⎝⎠⎛⎞+------------------------------------------------------------------------------------------------------------------------W n w 1w 2–w 2----------------C =αW nW n /C ()*C -----------------------W n 0.25C--------------==P t W 3W 1–W 3W 2–------------------=Table 2 Mixture proportions for c ement pastes.ID w/c (-)Cement (kg)Type of cementCP 0.3, 0.35, 0.4, 0.5, 0.6, 0.7300OPCTable 3 Mixture proportions for c onc rete spec imens.Specimenw/b (-)Water (kg m -3)Binder (kg m -3)Sand (kg m -3)Gravel (kg m -3)Type of cementC400.41403507421,135OPC C500.51583507241,107OPC C600.61753507071,080OPCTable 4 Mixture proportions for mortar spec imens.Specimen w/c (-)Water (kg)Cement (kg)Sand (kg)Type of cement M1-10.4120300300OPC M1-1.50.4120300450OPC M1-20.4120300600OPC M2-10.5150300300OPC M2-1.50.5150300450OPC M2-20.5150300600OPC M30.55165300600OPC M40.6180300600OPC M50.65195300600OPCInternational Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)│875. Validation of analytical model5.1 Model for cement pasteFor validating of the proposed model, the predicted values by Eq. (4) are comprised with data of other researchers as shown in Fig. 9. Figure 9 includes porosities derived from calculated phase compositions, the degree of hydration is assumed to be the valueof maximum and a specific volume of cement is 3.17×10-4 m 3kg -1.As expected, the capillary porosities decreased with the increase of the degree of hydration and the water/cement ratio for all specimens as shown in Fig. 10; capillary pore space is filled with cement hydrates by hydration reaction (pore volume of gel increases by degree of hydration). From the Fig. 10, the predicted values by Eq. (9) are very similar with the measurements.Table 5 Measured properties of c ement paste.TypeTime (days)137142891w/c =0.3W n (kg m -3)23.82 27.91 30.06 30.92 33.02 35.10 α (-)0.345 0.404 0.436 0.448 0.479 0.509 P p (-)0.269 0.225 0.201 0.178 0.170 0.159 w/c =0.35W n (kg m -3)-26.91 29.95 ---α (-)-0.390 0.434 ---P p (-)-0.315 0.285 ---w/c =0.4W n (kg m -3)24.34 31.93 35.45 38.64 42.69 41.78α (-)0.353 0.463 0.514 0.560 0.619 0.605 P p (-)0.376 0.315 0.271 0.257 0.227 0.226 w/c =0.5W n (kg m -3)24.60 30.89 36.68 44.74 46.26 51.97 α (-)0.356 0.448 0.532 0.648 0.670 0.753 P p (-)0.439 0.399 0.355 0.327 0.299 0.287 w/c =0.6W n (kg m -3)24.08 30.18 38.49 45.65 48.79 53.27 α (-)0.349 0.437 0.558 0.662 0.707 0.772 P p (-)0.496 0.475 0.421 0.394 0.382 0.340 w/c =0.7W n (kg m -3)23.82 30.96 38.04 48.18 51.06 56.45 α (-)0.345 0.449 0.551 0.698 0.740 0.818 P p (-)0.548 0.522 0.494 0.455 0.425 0.395Table 6 Measured properties of mortar.Specimen w/c Wn (kg m -3)α (-)P cap (-)Sand/cement M1-10.436.018 0.522 0.213 10.444.505 0.645 0.177 1M1-1.50.435.466 0.514 0.188 1.50.443.470 0.630 0.166 1.5M1-20.425.530 0.370 0.217 20.435.445 0.514 0.169 20.444.712 0.648 0.149 20.452.026 0.754 0.123 2M2-10.540.158 0.582 0.268 10.550.094 0.726 0.227 1M2-1.50.538.364 0.556 0.248 1.50.545.264 0.656 0.220 1.5M2-20.528.911 0.419 0.254 20.537.398 0.542 0.230 20.548.231 0.699 0.196 20.556.580 0.820 0.176 2M2-30.5529.514 0.428 0.276 20.5540.779 0.591 0.255 20.5550.057 0.725 0.214 20.5559.340 0.860 0.195 2M2-40.634.500 0.500 0.280 20.643.539 0.631 0.263 20.656.580 0.820 0.223 20.663.480 0.920 0.208 2M2-50.6534.500 0.500 0.308 20.6544.850 0.650 0.288 20.6558.650 0.850 0.238 20.6564.860 0.940 0.225 2Fig. 9 Relation between total porosity and water/cement ratio.For various degree of hydration, Figs. 11 and 12 show therelation between porosity and water cement ratio by the proposed model. The porosity of gel increases with the increase of the degree of hydration and decreases with water/cement ratio, but reverse tendency occurs to the critical water/cement ratio at full hydration because water is insufficient for full hydration.5.2 Model for mortarFig. 13 shows the experimental results and comparisonsbetween measured and predicted data by Eq. (19). It is thoughtthat predicted values are very close to the measured ones like thecement paste, the capillary porosity of mortar decreases withincreasing hydration. As shown in Fig. 13, high water/cementratio increases the pore volume of mortar.Mortar and concrete can not properly be described as thecomposites of coarse and fine aggregates in a matrix of cementpaste otherwise identical with the aggregate-free material. Themicrostructure of the paste close to the aggregate differs from thatof cement paste in bulk, and much of the paste in concrete ormortar places or lies in this category.Interface transition zone (ITZ) between aggregate and cementpaste has more pore space than bulk cement paste because thesurfaces of aggregates were closely covered with poorly crystallinematerial as CH(Ca(OH2). In this zone, it is up to about 30µmwide; the paste is of increased porosity and presumably low instrength.The porosity of cement paste in mortar and concrete differsfrom the aggregate-free cement paste. Therefore, property ofinterface transition zone on porosity must be considered for moreaccuracy. Figs. 14 and 15 show the relation between sand contentand capillary porosity. The capillary porosity of mortar with Fig. 10 Comparison of the calculated and measured capillaryporosities.Fig. 11 Relation between capillary porosity and water/cement ratio.Fig. 12 Relation between gel porosity and water/c ement ratio.Fig. 13 Relation between water/cement ratio and capillary porosity.Fig. 14 Relation between G/C ratios and capillary porosity (w/c = 0.4).88│International Jou rnal of Concrete Stru ctu res and Materials (Vol.3 No.2, December 2009)。