Evaluation of an Al-Zn-Mg-Li alloy_potential candidate as Al-sacrificial anode
《高压扭转工艺对Al-Zn-Mg-Cu合金组织与性能的研究》范文
《高压扭转工艺对Al-Zn-Mg-Cu合金组织与性能的研究》篇一一、引言在众多金属材料中，铝及其合金以其优异的机械性能、耐腐蚀性和良好的可塑性广泛应用于各种工业领域。
尤其是Al-Zn-Mg-Cu合金因其强度高、加工性能良好等特性而备受关注。
高压扭转（High Pressure Torsion，HPT）工艺作为一种新兴的塑性加工技术，通过高压力和扭转应力的结合，可有效改善合金的微观结构和力学性能。
本文将深入探讨高压扭转工艺对Al-Zn-Mg-Cu合金组织与性能的影响。
二、实验材料与方法1. 材料准备本实验选用的材料为Al-Zn-Mg-Cu合金，通过铸造方法获得原始铸坯。
2. 工艺过程对所选择的Al-Zn-Mg-Cu合金铸坯进行高温退火处理后，分别在不同条件下进行高压扭转处理。
3. 实验方法采用光学显微镜（OM）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等手段对处理后的合金进行微观组织观察，并利用硬度计和拉伸试验机等设备测试其力学性能。
三、高压扭转工艺对组织的影响1. 晶粒结构变化高压扭转处理后，Al-Zn-Mg-Cu合金的晶粒尺寸明显减小，呈现出更为细小的晶粒结构。
这有利于提高合金的强度和韧性。
2. 微观结构变化高压扭转过程中，合金内部出现大量的位错和亚晶界，这些位错和亚晶界的形成有助于提高合金的塑性和抗疲劳性能。
此外，合金中第二相粒子的分布也变得更加均匀，有利于提高合金的力学性能。
四、高压扭转工艺对性能的影响1. 硬度变化经过高压扭转处理后，Al-Zn-Mg-Cu合金的硬度显著提高。
这主要归因于晶粒细化、位错和亚晶界的形成以及第二相粒子的均匀分布等因素的综合作用。
2. 拉伸性能变化高压扭转处理后，合金的抗拉强度和延伸率均有所提高。
这表明高压扭转工艺能够有效地改善合金的塑性和韧性。
此外，经过高压扭转处理的合金在拉伸过程中表现出更好的均匀变形行为。
五、讨论与展望通过对Al-Zn-Mg-Cu合金进行高压扭转处理，我们发现该工艺能够显著改善合金的微观结构和力学性能。
新型粉末冶金制取Al-Zn-Mg-Cu合金的金相评估
新型粉末冶金制取Al-Zn-Mg-Cu合金的金相评估关键词：铝的粉末冶金Al-Zn-Mg-Cu合金热辐射量高温拉伸疲劳强度摘要这个课题的目的，是对粉末冶金制取的Al-Zn-Mg-Cu新合金（也称为Alumix 431D）进行详细的显微组织和力学性能评估。
这项工作需要一系列技术手段，包括显微分析、X射线衍射分析、电子探针显微分析热膨胀分析、差示扫描量热分析一级表面硬度的测定、拉伸测试、弯曲疲劳强度测试。
Alumix 431D显示出许多与之相似组成的铸造件的性能如7075。
它的烧结密度达到了理论值的99%，这表明此合金具有很好的烧结性能。
再经热处理，室温下测得的硬度可达86HRB，最终拉伸强度达488MPa。
热学分析表明，Alumix 431D的析出行为与7XXX系铸造合金类似，大量的析出η相组织。
在150℃以上温度保持1000h进行T1(不预先淬火的人工时效)条件处理，此合金表现出相对稳定的拉伸性能。
1.简介随着汽油价格的上涨和环境保护的重视，汽车制造商开始寻找减轻汽车部件的办法。
因此，很多铁基部件被铝基产品所代替。
为了加速这个替换过程，低成本金属的加工流程是十分重要的。
压力烧结粉末冶金是近年来引起广泛关注的制造铝合金方法。
这个方法利用A6061、AC2014、4XXX系三种铝基合金，具有很好的商业利用价值[1-3]。
此粉末冶金过程是用基本的合金粉末混合来生产合金产品。
混合好的粉末倒入模具中，在高压下压实，而不是将熔融的金属倒入铸模中。
然后把压实的粉末在可控气氛熔炉中烧结成型，得到的产品不需要再进行机械加工了。
粉末冶金的净成形特点是它在与普通的铸造、浇注、挤压工艺竞争中有很大的优势。
虽然市场对铝的P / M的需求持续增长，很多机会仍然因为市售合金的数量有限，尚未开发。
许多公司通过基于7XXX（Al-Zn-Mg-Cu系）系列高强度合金的发展已经解决了这个问题。
当中包括由安帕尔，Toyal美国和俄卡生产商的共混物颗粒[4,5]。
应变速率对Al-Zn-Mg合金室温拉伸性能的影响
张臻奪::应变速率对A l-Zn-M g合金室温拉伸性能的影_响文章编号：1〇a i-9 73.1(2017)07-07 215-0 607215应变速率对Al-Zn-M g合金室温拉伸性能的影响'张臻^,邓运来“2,3,郭辉1>3，钱鹏传i’3,，唐鸿远2，叶凌英2(1•中南大#轻会金研究脘，长沙41.00.8.3;2•中南太:学材_料科攀院，长抄410.083;3..中亩大学有色金顧先进结构材料与制翁协筒创新中心，长沙4K)()83)摘要：研究了 .应变速率对A l-Zn-M g合金重温.拉伸性能的_影响Q结果表明，随着试验过程中应.变速率的增 加，A l-Z:n-M g合金的叙限抗拉强度(i?M)略有_增加，屈服强度明显上升，伸长率显著下降。
断口显微 分析表明，在应变速率较低时，A l-Zn-M g合全材料的翁口中初窝组织较多.，主要以初性断:裂为主；随着.应变速.率 不断增加，表现出初性断裂和脆性断裂^:金相显微分析表明，随着:应变速率的增加，断口的纟从剖面晶粒伸长减少，并出现一些细小的析出相。
此外，基于Fields-Hackofea本构方程模型，定#分析计算了应变速率对A l-Zn.-M g合 金拉伸性能的影_响。
关键词：A l-Zn-M g铝合金；应变速率；拉伸性能 ;Fields-Backofen本构方程中图分类号：文献标识码：A D O I：l〇»3aS9/j.issn.1QQl-l?731i2〇17,0?.042〇引言随着现代科技的不断发展•军航空航天以及轨道交通运输对材料综合性能要求越来越苛刻，现有的 材料以无法满足其需隶。
在环境保护以及成本控制的 驱使下，结构材料的轻犛化成为了.发展的趋势[1—fl。
A l-Zn-M g合金疆其密度小、比强度、比模量_s导电、导热性能好等特点•得到了广泛的应用。
但是，A l-Zn-M g合金在室温下塑性较差，成形相 对比较困难，而温成形工艺则可以提高铝合金材料的成形性能p在温成形过程中，招合金材料的塑性可适缉増加，流变抗力有所降低，同时在较高的温度下•会产生应力松弛现象，降低了倒弹，因而可提高铝 合金件的成形精度[1:—15]s本文对A l-Zn-M g合金挤压材进行温拉伸试验•获得了不同应变速率下的拉伸性能指标以及流变应力 曲线•建重该合金合埋的材料模型，为进一步研究A1-Z n-M g合金的温成形性能奠定:了基础B1 实验1.1实验材料A l-Zn-M g合金挤压材，实验室爾制，其主要化学成分见.表:_1所示，其中好e:和S i为主要杂质:麗氟酸(H F)，国药集团化孛试剂有限公司，分析纯（A R);盐 酸（H C U，株洲市崖备化破有限公_■:，分析纯（A R h硝 :酸.1H N(V)株洲:市星空玻有限公苛，分析纯.(AR.);氧化铬（c r a),西陇化j t股份有限公司•分析纯(A R)0表1A l-Z n-M g合金的化学成分（％,质量分数）Table：1Coniposition of A l-Zn-M g alloys[%,masa fra ctio n)元素Zn Mg Cu Mn Cr Zr Ti Si Fc八1含量 4.27 1.390.110.320.110.140.0740.0710.17Bal.1.2实验设备电子万能材料试验机，m x-io o，长春机械科李研 有限.公荀Y金相显微镜、O LY M P U S- _D SX500, H:本O L Y M P A U S公贫s扫播电乎赫微镜Qua:n-ta-200•美国F E I公司。
Corrosion of an Al–Zn–In alloy
Corrosion of an Al–Zn–In alloy in chloride mediaA.G.Mu ~noz,S.B.Saidman,J.B.Bessone *Departamento de Qu ımica e Ingenier ıa Qu ımica,Instituto de Ingenier ıa Electroqu ımica y Corrosi o n (INIEC),Unive rsidad Nacional de l Sur,Av.Ale m 1253,8000Bah ıa Blanca,ArgentinaReceived 14November 2000;accepted 12February 2002AbstractIn order to explain the electrochemical behaviour of Al–Zn–In based alloys in chloride media,a commercial Al–Zn–In–Si anode and a ternary alloy,Al–5%Zn–0.02%In prepared in our laboratory,were investigated using potentiodynamic techniques,complemented by SEM,EDX and TEM.The influence of alloy composition,agitation and previous cathodisation on the electrochemical response of the alloys was analysed.Results of previous investigations with pure metals (Zn and In)and with binary alloys (Al–In,In–Al,Zn–In)are also considered in this paper for the sake of comparison.The attack initiation on the Al–Zn–In alloy is related to In–Zn rich zones,segregated at grain boundaries.The presence of In in true electric contact with Al and Zn promotes Cl Àadsorption at potentials more positive than À1.1V.Then,the presence of Zn facilitates a surface enrichment of indium by a displacement reaction.This in turn,assures an accumulation of adsorbed Cl À,which maintains an active state of the Al matrix.Ó2002Elsevier Science Ltd.All rights reserved.Keywords:A.Aluminium;Al–Zn–In alloy;Corrosion;Chloride;Sacrificial anode1.IntroductionThe economic advantages of exploiting the high theoretical current capacity and the low active potential of Al as an anode have long been appreciated,although the spontaneous formation of oxide on Al exerts a strong passivation effect.Acti-vation of Al is obtained through a localized attack in the presence of aggressive anions,once a defined potential is exceeded in the anodic scan.The operating potential (pitting potential)makes Al unsuitable as a sacrificial anode.Therefore,/locate/corsciCorrosion Science 44(2002)2171–2182*Corresponding author.Tel./fax:+54-291-4595182.E-mail address:jbessone@.ar (J.B.Bessone).0010-938X/02/$-see front matter Ó2002Elsevier Science Ltd.All rights reserved.PII:S 0010-938X (02)00042-22172 A.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–2182alloying elements are used in order to shift it towards sufficiently electronegative values and to produce a more uniform attack morphology.Since the number of permutations of alloying additions is vast,it seems improbable that significant im-provements in anode performance can be achieved from further trial-and-error procedures.Rather,a fundamental understanding of the relationships between the anodic response of these alloys(related to the operating potential)and the metal-lurgy(related to the attack morphology and therefore to the current capacity)is needed.From commercially produced Al sacrificial anodes,there is little doubt today that Al–Zn–In base anodes present the best performance in seawater[1,2].The average operating potential of Al–Zn–In anodes in this media isÀ1.1V vs.SCE.The acti-vator elements(Zn,In)ensure a uniform dissolution of the anode and avoid po-larization.The attack morphology of an Al–5%Zn–0.02%In alloy in seawater shows hemispherical pits with a relatively smooth surface[3].The same morphology was obtained with an Al electrode activated in the presence of In3þand Zn2þ[4].It has been proposed that the current efficiency(i.e.the attack morphology)depends on the solidification microstructure,which in turn depends on heat treatment and aging time[5].It seems reasonable then to assume that one way to obtain this fundamental understanding lies in a better knowledge of the electrochemistry of the Al–Zn–In alloy.Important data mainly related to the activating elements and the pitting process have been collected.Previous studies suggest that the initial step in the dissolution mechanism of the Al–In alloy can be interpreted through chloride ad-sorption on the In–Al alloy[6].Considering now the influence of Zn on Al activa-tion,the active behaviour of Al in chloride solutions containing Zn2þand In3þwas explained taking into account the displacement reactions that produced In accu-mulation and preferential Zn dissolution[4].A higher instability of the Al oxide layer due to the formation of ZnAl2O4[7]and a decrease of the pH of zero charge of the oxide[8]are also possible factors,which explain the role of Zn on the activation process.It has been postulated that a small amount of alloyed Zn has an effect mainly,or exclusively,on propagation and repassivation of metastable pits and not on their nucleation frequency.A large amount of alloyed Zn enhances the dissolu-tion kinetics in the local environment,facilitating the transition to stable pitting[9]. The presence of impurities determines the type of attack.No activation is obtained with99.61%Al in the presence of an In3þconcentration below10À2M[10].De-position of In takes place on the oxide layer and/or at the iron impurities,thus preventing direct contact of In with Al[11].The aim of this paper is to get a better knowledge of the electrochemical response of the Al–Zn–In based alloy.In this sense,the anodic behaviour of the Al–Zn–In alloy,prepared in our laboratory,and that of the commercial Al–Zn–In–Si anode are compared with those of pure metals(Zn and In)and binary alloys(Al–5%Zn, Zn–5%In,and Al–5%In)in0.5M NaCl solution of pH5.In the case of the com-mercial alloy,Si acts as a grain refiner and as entrapment for Fe impurities,en-hancing its efficiency.It does not play,however,any role in defining its operating potential[12].The analysis of the synergistic activation effect,produced by the co-A.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–21822173 deposition of Zn and In on Al or the binary systems,is expected to give a better understanding of the ternary alloy behaviour.2.ExperimentalThe ternary alloy Al–5%Zn–0.02%In(composition according to Table1)was obtained using pure Al,Zn and In(Aldrich Chemical Co.),which werefirst etched in 2%nitric acid in ethanol and then placed into a cylindrical graphite crucible.A heating procedure already explained elsewhere[6]was followed and then cast in cold water.Due to the very low solubility of In and Zn in Al at ambient temperature[13] and the nominal composition used,In and Zn rich phases are expected.Higher solubilities are then possible as a consequence of quenching.A commercial Al–Zn–In–Si alloy,whose composition is also shown in Table1,was used for comparative purposes.Cylindrical rods were mounted in a PTFE holder,configuring a disk electrode with a diameter of7mm.Electrodes were polished with1000grade emery paper and0.3l m alumina suspension and then rinsed thoroughly with triple-dis-tilled water.Chloride solution(0.5M NaCl)was prepared from analytical grade chemicals and triple-distilled water.The pH was adjusted to5with HCl.A large Pt sheet was used as the counter electrode.A SCE was used as a reference electrode and potentials are referred to this.All experiments were performed with still electrodes unless otherwise stated(rotating disk electrode).The experiments were carried out in a purified N2saturated atmosphere at25°C. Potentials were applied using a potentiostat–galvanostat(PAR Model173)after20 min of stabilisation at the rest potential.Potentiodynamic polarizations were per-formed at0.001V sÀ1.Once the corrosion potential was attained,a polarisation towards cathodic potentials was applied.After electrode polishing and restoring of corrosion potential,the polarisation towards anodic potentials was carried out. Results were corrected for ohmic drop using the solution resistance obtained from impedance measurements.From the results of at least three runs,a fairly good re-producibility with variations belowÆ5%was attained.A rotation rate of2600rpm was used with rotating disk experiments.A dual stage ISI DS130SEM and an Table1Composition analysis of the pure Al–Zn–In and the commercial Al–Zn–In–Si alloysElements Al–Zn–In(wt.%)Al–Zn–In–Si(wt.%)Zn 4.970 4.1065In0.0210.01Si0.0150.093Fe0.0770.120Cu0.0220.034Cd0.0030.012Pb0.0250.042Al Remainder RemainderEDAX 9600quantitative energy dispersive X-ray analyser were used to examine the electrode attack.Previously samples were gold coated.TEM analysis was also per-formed using a Jeol JSM 100CXII.In this case the ternary alloy was embedded into an epoxy resin and trimmed to 1mm 2.From this specimen,ultramicrotomed sec-tions (300–500l m thick)were obtained by means of a LKB 8800Ultratome III ultramicrotome.3.ResultsThe potentiodynamic polarization curves of the Al–Zn–In alloy,the commercial alloy,Zn and In in deareated 0.5M NaCl solution are shown in Fig.1a.Results obtained at the same conditions with binary alloys (Fig.1b)are also incorporated for the sake of comparison.The corrosion potential of Al–Zn–In was about À1.3V.The shape of the anodic curve of the commercial alloy is very similar to that obtained with the ternary alloy.In this case,hydrogen evolution is enhanced by the presence of impurities and the E corr is now À1.1V.Preferential attack at the grain boundary extending into the grain body was found when the ternary alloy was polarized at À0.95V and examined by SEM (Fig.2a).At higher magnification (marked area in Fig.2a),corrosion products at the grain boundary and a hole can be observed (Fig.2b).X-ray maps indicate In and Zn enrichment at the grain boundary (Fig.2c).Initiation and propagation of the attack is associated with the alloy microstructure and composition.It was corroboratedby 2174 A.G.Mu ~n oz e t al./Corrosion Scie nce 44(2002)2171–2182metallographic observations of the corroded surface after holding the alloy at À1.0V for 20min (Fig.3a).Dissolution was preferentially started at both grain boundary regions and along the cell boundaries formed during the retrograde (k <1,k ¼partition coefficient)solidification process.A particular feature may be ob-served (Fig.3b)at higher magnification:a localized attack at cell boundariesand Fig.2.(a)SEM micrograph of Al–Zn–In alloy after being anodically polarized in deareated 0.5M NaCl solution of pH ¼5from E corr ,towards anodic potentials,to À0.95V,v ¼0:001V s À1.(b)Higher mag-nification of the corrosion products at the grain boundary.(c)X-ray maps (Zn-L a and In-L a signals)of the corrosion products indicating In and Znenrichment.Fig.3.(a)SEM micrograph of Al–Zn–In alloy after being anodically polarized at À1.0V for 20min in deareated 0.5M NaCl solution pH ¼5,E i ¼E corr ,v ¼0:001V s À1.(b)Higher magnification following the cell boundaries.A.G.Mu ~n oz e t al./Corrosion Scie nce 44(2002)2171–218221752176 A.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–2182feather-like corrosion products emerging from holes.A similar behaviour was ob-served on the commercial alloy,but related to a small grain size given,as expected, by the refinement action of Si.Preferential dissolution started at grain boundary regions was observed after holding the sample for2h at open circuit conditions (E¼À1:1V).H ere,Zn and Si segregated zones were detected by X-ray analysis.The presence of indium was not observed,it being possible due to its low level in the commercial alloy.To obtain information about the influence of the microstructure on the activation process,thinfilms cut from this alloy were analysed by TEM(Fig.4a and b).They show the presence of spheroidal precipitates of different size,from2.5to0.2l m, some of them located on a quasi-straight line.In order to identify these particles and different zones around them,electron diffraction patterns corresponding to the points A,B and C showed in Fig.4a were obtained(Fig.5a–c).Precipitates were identified as In particles by comparing the measured crystallographic plane distances with those reported for pure In(Table2).The diffraction patterns of points B and C do not allow to distinguish between Zn and Al,suggesting the presence of a Zn–Al solid solution.Additional and interesting results of the behaviour of the ternary alloy were obtained with a polarization initiated atÀ1.8V with and without electrode rotation (Fig.6).It is known that hydration and/or dissolution of Al oxide takes place by local alkalisation when Al and Al alloys are polarized at relatively high cathodic potentials.Thus,a previous polarization atÀ1.8V for5min ensures a quasi-bare Al surface.The profile recorded without rotation shows that the current density changed its sign atÀ1.54V and tends to a constant value of%30l A cmÀ2between À1.4andÀ1.2V(Fig.6).This behaviour may be mainly attributed to an initial Al dissolution through the quasi-dissolved oxide generated by the local alkalisation [14,15].At higher anodic potentials the hydrogen evolution reaction(HER)is re-duced and the oxidefilm is re-established,so limiting the rate of Al dissolution. Then,the anodic dissolution of Al,assisted by ClÀadsorption,initiates atÀ1.1V,as will be later explained.Under rotation,the possibility of a local pH increase waspolarizationminimized and a similar curve to that in Fig.1is obtained.The Array Fig.4.TEM examination of samples cut from the Al–Zn–In alloy:(a)Â10000,(b)Â20000.behaviour obtained at potentials more positive than À1.1V is very similar to that obtained without previous cathodization (Figs.1and 6).The same type of attack is also obtained under these two conditions,suggesting an independence of the char-acteristics of the active surface from the previous alkalisation.4.DiscussionThe operation potential of commercial Al–Zn–In alloys has been widely reported to be around À1.1V in different chloride media.The E corr for the ternary alloy studied here is around À1.3V.In spite of this,Fig.1shows a depolarised anodic kinetics in chloride media,where the potential of both alloys practically does not change in the range from 102to 104l A cm À2.The effects produced by In and Zn on Al will be discussed in terms of the activation potential and the depolarised anodic kinetics.It has been demonstrated,that once the potential of zero charge (pzc)of aluminium in chloride solutions is anodically exceeded,migration,adsorptionand Fig.5.Electron diffraction pattern for points A,B and C in Fig.4a:(a)point A,(b)point B and (c)pointC.A.G.Mu ~n oz e t al./Corrosion Scie nce 44(2002)2171–21822177Table 2Comparison of plane distances calculated from electronic diffraction patterns obtained for points A,B and C in Fig.4a and those corresponding to the pure elements Al,Zn and InPoint APoint B Point C Al (hkl)a cubic fcc A 0:4.0494 A Zn (hkl)b hexagonal A 0:2.665 A ,C 0:4.947 A In (hkl)c tetragonal fcc A 0:3.2517 A ,C 0:4.9459 A 2.933 2.5142.588 2.338(100) 2.473(002) 2.715(101)2.2562.256 2.308(100) 2.471(002)2.024(200) 2.091(101) 2.298(110)1.795 1.5431.600 1.431(220) 1.687(102) 1.683(112)1.353 1.353 1.342(103) 1.625(200)1.517 1.332(110) 1.470(103)1.221(311) 1.237(004) 1.395(211)1.169(222) 1.173(112) 1.358(202)1.189 1.153(200) 1.236(004)1.123(201) 1.149(220)1.090(104) 1.090(213)1.011 1.023 1.012(400) 1.045(202)0.9160.928(331)0.945(203)0.9070.905(420)0.909(105)0.8540.826(422)aSwanson and Tatge,JC Fel.Reports NBS (1950).b Ibid.(1951).c Swanson and Fuyat,NBS Circular 539,vol.III(1953).2178 A.G.Mu ~n oz e t al./Corrosion Scie nce 44(2002)2171–2182accumulation of ClÀat imperfection sites of the oxide are the main factors for pitting initiation[16].The adsorption of ClÀhas been postulated as a step on the Zn oxi-dation mechanism[17].On the other hand,a value ofÀ0.96V for the pzc was reported in this media[18].As a consequence,a depolarised anodic reaction,con-trolled by diffusion of ZnCl2Ànn species from the surface to the bulk solution[19,20],isobtained(Fig.1a).The increase of ClÀconcentration at the Al surface,given by the adsorption process sustained by Zn present in enriched Zn zones of the Al–5%Zn alloy,possibly as a phase[21],shifts the active potential to the well known value of À0.96V[3].Taking into account the electrochemical behaviour of In in chloride(Fig.1a) [22,23],as well as in alkaline media[24],a strong adsorption of ClÀor OHÀwas found onceÀ1.1V is anodically exceeded,in spite of a massive dissolution taking place at more positive potentials.It means that In promotes an enrichment of ClÀat the metal surface at E>À1:1V.The influence of In on the anodic dissolution of Zn has been recently analysed by kinetic studies and impedance spectroscopy(EIS) performed on Zn and the binary alloy Zn–5%In in ClÀmedia[25].The presence of In as a segregated phase at the grain boundaries or as an In rich phase in the inter-dendritic zones of the grains promotes higher dissolution rates as well as a higher overpotential for the HER.Both facts shift the corrosion potential of the alloy and its depolarised active potential region towards more negative values.This active potential region quasi matches that of the ternary and commercial alloy(Fig.1a).On the other hand,the strong ClÀadsorption exerted by In on In rich phases or possible surface In–Al alloys brought about by deposition,promotes its activation at more electronegative potentials than that corresponding to pure Al(E<À1:1V,Fig.1b) [6].This activation potential practically matches that of the ternary alloy(Fig.1b). No matters the amount of In used in the nominal composition,only the little amount of indium present as solid solution in Zn and Al will be responsible for the anodic electrochemical behaviour.For this reason,the electrochemical response of an Al–0.09%In and Al–5%In are practically the same[6].Now,it is worthily to compare the behaviour of the binary Al–In and Zn–In alloys(Fig.1b)with that of the ternary alloy.A nominal composition of5%In was used to be sure that a sufficient amount of In as solid solution is present in the Al–In or Zn–In alloys.Then,the comparison with the electrochemical behaviour of pure Zn should help to observe its contribu-tion to the activation of the ternary alloy.The presence of pure In seems here not to exert any influence.What is the role played by Zn?The electrochemical behaviour of the ternary and commercial alloy in Fig.1can be explained considering the syner-gistic effect of In and Zn on Al.It has been demonstrated that Al is activated when it is placed in neutral solutions containing In3þand Zn2þ[4].Deposition of Zn and In on bare Al is possible and it should present a similar situation to that given by the active interface of an Al–Zn–In alloy used as an anode material.The active be-haviour of Al in chloride solutions containing In3þand Zn2þwas explained con-sidering displacement reactions,which produced an accumulation of In and a preferential Zn dissolution.The presence of In at the bare Al surface favours chloride adsorption,so avoiding repassivation.Furthermore,the hydrolysis of Al3þis a strong exothermic reaction.Thus,it may lead to temperatures within an activeA.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–218221792180 A.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–2182pit high enough to facilitate the surface diffusion of In and Zn.The much lower mobility of Zn compared with that of In and its tendency to dissolve from the surface explain the decreasing concentration of Zn at the interface[26].In this way the presence of Zn at the active interface promotes In enrichment.This,in turn,facili-tates ClÀadsorption and its surface enrichment at potentials more positive thanÀ1.1 V,considered as its pzc.This surface condition promotes and maintains the acti-vation of Al.Therefore,it is expected that the attack will initiate and propagate in those zones enriched in In and Zn during the solidification process,i.e.,grain boundaries and interdendritic zones.Comparing the ternary alloy with the commercial one(Fig.1a),practically the same anodic behaviour is obtained,although differences appear in the E corr values. This fact may be explained considering the higher amounts of cathodic impurities present in the commercial alloy(Table1).These impurities produce higher polar-ization of the anodic areas,leading to the chloride adsorption potential on In–Zn rich zones.Thus,the E corr of the commercial alloy attainsÀ1.1V and remains in this value.Accordingly,the surface attack observed after maintaining this electrode at the open circuit potential for2h was mainly located at grain boundaries.In the ternary alloy,the cathodic impurities are not enough to polarize the anodic areas to this value,and practically no chloride assisted attack is obtained at its E corr.Fig.2shows how the attack initiates at grain boundaries and propagates into the bulk of the grain through interdendritic zones.The corrosion products observed in Fig.2b and their X-ray maps demonstrate the presence of In and Zn enriched phase. The extremely low solubility of In in Zn and Al explains this segregation[13].The same result is sustained in Fig.3a when the alloy is maintained atÀ1.0V for20min. The grain and cell boundaries,as well as interdendritic zones are the main active regions.Thus,the initiation of the attack generated by these enriched In–Zn zones explains the coincidence between the anodic response of the ternary alloy with the binary Al–In and Zn–In alloys.Some localized attack in the bulk of the grains is also observed,especially after the propagation of the attack has been taken place(Fig.3b).By analysis of the electron diffraction patterns performed on points A,B and C(Figs.4a and5a–c),the iden-tification of these particles and the surrounding areas was intended.According to the composition of the ternary alloy,a quite ductile material is being handled.This means that a highly disordered surface and crystal deformation are expected when thin slices of less than1000 A are cut.Indeed,the apparent dark regions represent extinction contours.At point A,the diffraction pattern shows points symmetrically ordered around the main central spot,so they correspond to the same diffraction plane.Considering the high distance between planes,the point A can be attributed to a rich In phase.Due to a poor hardness of In,a considerable crystal deformation explains the variation of plane distances found with respect to pure In and the light shaded diffraction spots in Fig.5a.Therefore,these precipitates were identified as In particles when distances between crystallographic planes were compared(Table2) with that of pure In.Besides,this was corroborated by EDX analysis.The diffraction pattern at point B and C does not permit to distinguish between Zn and Al.TheA.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–21822181 plane distances are closer to those corresponding to Zn.However,the presence of Al in metastable solid solutions is possible due to the method used to obtain the alloy (fast quenching process).This fact may explain the higher plane distances compared with those of pure Zn and the missing of diffraction planes as a consequence of interference effects.Here,the diffraction corresponding to high index planes suggests the presence of a Zn–Al solid solution.These results indicate that In precipitates of significance size,distributed in the Al matrix,are responsible for the localized attack observed within the grain(like holes).Further,the location of these particles along a straight line(Fig.4b)seems to be related to a segregation process of In to cell boundaries(Fig.3a and b).It has already suggested[5]that the presence of In as solid solution not only promotes a smooth and uniform attack but also a maximum current efficiency.This particular attack morphology is,however,still a matter of discussion and further work is needed on this issue.5.ConclusionsThe observed electrochemical behaviour of the ternary alloy may be explained in terms of the following statements:(i)The attack initiation of the Al–Zn–In alloy is related to In–Zn rich zones,lo-cated at grain or cell boundaries.(ii)The presence of In in true electric contact with Al and Zn promotes ClÀadsorp-tion at potentials more positive thanÀ1.1V,considered as the pzc of such inter-face.(iii)The presence of Zn facilitates a surface In enrichment by a displacement reac-tion.This,in turn,assures an accumulation of adsorbed ClÀwhich maintains an active state of the Al matrix.AcknowledgementsFinancial support from Secretar ıa de Ciencia y T e cnica UNS(UNS-CSU-170/99) is acknowledged.Also,one of us(A.G.M.)thanks CONICET for a grant. References[1]C.F.Schrieber,R.W.Murray,Mater.Performance27(1988)70.[2]S.L.Wolfson,Mater.Performance33(1994)22.[3]J.B.Bessone,R.A.Suarez Baldo,S.M.de De Micheli,Corrosion37(1981)533.[4]S.B.Saidman,A.G.Mu~n oz,J.B.Bessone,J.Appl.Electrochem.20(1999)245.[5]J.C.Lin,H.C.Shih,J.Electrochem.Soc.134(1987)817.[6]S.B.Saidman,S.G.Garc ıa,J.B.Bessone,J.Appl.Electrochem.25(1995)252.[7]C.B.Breslin,L.P.Friery,Corros.Sci.36(1994)231.[8]P.M.Natishan,E.Mc Cafferty,G.K.Hubler,J.Electrochem.Soc.135(1988)321.2182 A.G.Mu~n oz e t al./Corrosion Scie nce44(2002)2171–2182[9]F.Sato,R.C.Newman,Corrosion3(1999)55.[10]H.A.El Shayeb,F.M.Abd El Wahab,S.Zein El Abein,J.Appl.Electrochem.29(1999)601.[11]C.B.Breslin,L.P.Friery,W.M.Carroll,Corrosion49(1993)895.[12]S.N.Smith,J.T.Reding,R.L.Riley Jr.,Mater.Performance17(1978)32.[13]H.Baker,H.Okamoto(Eds.),ASM Handbook,vol.3,ASM International,Materials Park,Ohio,1992.[14]S.M.Moon,S.I.Pyun,Corros.Sci.39(1997)399.[15]H.Yan,J.Downes,P.J.Boden,S.J.Harris,J.Electrochem.Soc.143(1996)1577.[16]A.G.Mu~n oz,J.B.Bessone,Corros.Sci.41(1999)1447.[17]J.Ban a s,K.G.Sch€u tze,E.Heitz,J.Electrochem.Soc.133(1986)253.[18]L.M.Baugh,J.A.Lee,J.Electroanal.Chem.48(1973)55.[19]S.Asakura,K.Nobe,Corrosion40(1994)227.[20]L.M.Baugh,Electrochim.Acta24(1979)657.[21]D.R.Salinas,S.G.Garc ıa,J.B.Bessone,J.Appl.Electrochem.29(1999)1063.[22]A.G.Mu~n oz,J.B.Bessone,Electrochim.Acta43(1998)2033.[23]A.G.Mu~n oz,S.B.Saidman,J.B.Bessone,J.Electrochem.Soc.146(1999)2123.[24]S.B.Saidman,E.C.Bellocq,J.B.Bessone,Electrochim.Acta35(1990)329.[25]A.G.Mu~n oz,S.B.Saidman,J.B.Bessone,Corros.Sci.43(2001)1245.[26]S.B.Saidman,J.B.Bessone,J.Appl.Electrochem.27(1997)731.。
Zn粉辅助Al？Mg异种合金搅拌摩擦搭接连接
第44卷第4期2018年8月兰州理工大学学报Journal of Lanzhou University of TechnologyVol. 44 No. 4Aug. 2018文章编号：1673-5196(2018)04-002灢06Zn粉辅助Al/M g异种合金搅拌摩擦搭接连接金玉花，吴永武，毕胜，王希靖，郭廷彪(兰州理工大学省部共建有色金属先进加工与再利用国家重点实验室，甘肃兰州730050)摘要：对厚为2 m m的镁合金AZ31B和铝合金6061-T6板材搭接面涂敷Z n粉诱导搅拌摩擦搭接连接.采用光学显微镜（O M)、扫描电子显微镜（FEG-450)、能谱仪（E D S)研究了焊接速度为50 mm/m i n，不同转速600〜1 400 r/m i n下接头的组织，并用显微维氏数值硬度仪和剪切试验对接头的力学性能进行了表征，同时用XRD对剪切断口进行了分析.结果表明：Zn粉的加入可有效阻止镁铝之间的互扩散，降低脆性相A l-M g系金属间化合物的产生，提高了镁/铝搭接接头的抗剪切载荷，改善了接头的力学性能.关键词：镁合金；铝合金；锌粉涂层；搅拌摩擦焊；组织；接头力学性能中图分类号：TG457 文献标志码：AZn powder-assisted friction stir lap welding of Al/Mgheterogeneous alloying platesJI N Y u-h u a,W U Y o n g-w u,B i-S h e n g,W A N G X i-jin g,G U O T ing-biao(State Key Laboratory of Advanced Processing and Recycling of Nonferrous M etals, Lanzhou Univ.A b stra c t ：Zn powder was coaded on the lapping surface of 2 mm-thick AZ31B Mg and 6061-T6Al alloying plates to assist their friction stir lop welding.The microstruture of their joint was investigated under welding speed of 50 mm/min and rotation speed from 600 r/min to 1 400 r/min with optical microscope (OM),scanning electron microscope (SEM)FE G-450 and energy dispersion spectroscope(ED S),the mechanical properties of the-oint were characterized by means of microscopic Vickers numeric hardness and shear test,and the shearing fracture was analyzed with XRD.The result showed that the powder could effectively prevent the mutual diffusion between Mg and A l,reduce the formation of brittleAl-Mg intermetallic compounds,enhance the shearing strength of the-oint?and improve its mechanical properties.K ey w ords ：Mg alloy；Al alloy；zinc powder coating；friction stir welding；organization；mechanical property目前，车身轻量化已成为汽车行业节能减排的热点，轻质材料在车身上的广泛应用必将成为车体轻量化的关键要素，因镁合金和铝合金等具有高的比强度、低密度、良好的铸造性能以及优异加工性能 而备受青睐，其中A l/M g异种材料的优良连接是科 研工作者需要探究的问题之一.由于Mg/A l异种金 属焊接时焊合区容易产生大量的A-M g系金属间 化合物（intermetallic compounds，IMCs).IMC具有 硬脆特性，容易导致Mg/A l异种金属接头处产生裂收稿日期：2017-11-10基金项目：国家自然科学基金（51261016)作者简介：金玉花（1971-)女，甘肃兰州人，博士，副教授.纹而形成弱连接，从而对M g/A l合金接头的力学性能产生恶化作用[13].为了提高接头力学性能，许多 研究者在电阻点焊[4—5]、传统熔焊[6—7]、压力焊[8—12]或 者其他焊接技术[1316]的界面处添加中间层来有效抑 制异种金属过渡层金属间化合物的生成.Zhang等[]采用热补偿电阻点焊对夹人锌箔的镁铝异种金 属进行了焊接.焊核区存在M g-Zn化合物以及Al 固溶体使其相比于焊核区为M g-A l化合物的接头 性能获得进一步的提高.G a o等[]利用激光焊对加人T i夹层的M g/A l异种金属接头进行了分析，发 现A l-M g系金属间化合物的生成被抑制，进而生成 A l T i和少量的A l8T i2M g3化合物，界面硬脆性降第4期金玉花等：Z n 粉辅助Al /M g 异种合金搅拌摩擦搭接连接•27•低.王希靖等[]用T 2紫铜与H 62黄铜异种材料进 行了搅拌摩擦焊工艺研究.接头交界处存在过渡带， 宽度约为1〜1〇Mm 的过渡物质.研究还发现接头 显微硬度、平均抗拉强度介于黄铜与紫铜之间.Me - shram 等[2]将 A g 夹层置于 A A 6061 和 AISI 4340 界面处进行了摩擦焊，发现界面存在具有韧性的 A g -A l 化合物，该化合物的存在使得接头的力学性 能得到大幅度提升.但对于Mg /A l 搅拌摩擦搭接焊 (friction stir lap welding ，FSLW )，添加一^定厚度的 中间Z n 涂敷层改善接头组织与性能的研究仍然不 多.因此本文对A Z 31B /6061-T 6合金板材中间添加 Z n 粉涂层进行了搅拌摩擦搭接焊辅助的A l/M g 接 头搭接试验，并对其接头组织与性能进行了分析.1实验焊接试验选用6061-T 6铝合金和A Z 31B 镁合金轧制板材，其尺寸120 mmX 120 mmX 2 mm .铝 合金 6061 化学成分为 w (Mg ) = 0. 967 8%，w (Si ) = 0. 552 7%，w (Cu )=0. 217 5%，w (Fe )=0. 140 1%， Al -bal ;镁合金A Z 31B 的化学成分为w (A l )= 3.0%，w (Zn ) = 1. 0%，w (Mn ) = 0. 4%，w (S i ) = 0. 1%，Mg -bal .焊前利用钢丝刷去母材表面的氧化 层，利用丙酮去除表面的油污，用丙酮调制Z n 液并 均匀地涂于铝板与镁板搭接界面处，然后利用夹具 对两板进行固定，采用锥台形搅拌头进行焊接实验. 锥台形搅拌头基本尺寸为：轴肩直径16 mm ，轴肩 面内凹（内凹角2°)，搅拌针长度为1.8 mm ，搅拌针 根部直径为5 mm ，端部直径为4 mm .搅拌针旋转 速度为600〜1 400 r/min ，焊接速度恒定50 mm /min ， 下压量为0. 15 mm .搅拌摩擦搭接焊如图1所示. 将每个参数下得到的焊件沿垂直于焊缝方向切割， 得到尺寸为20 mmX 12 mmX 3. 8 m m 的金相试样，拋光后用腐蚀剂（3 g 苦味酸+ 2.5 m L 乙酸+ 5 mL 蒸馏水+ 45 m L 乙醇）腐蚀30 s 左右，然后分析微 观组织和显微硬度.拉伸剪切试样尺寸为120 mmX 15 m m X 3. 8 mm ，每个参数下准备3个剪切试样. 用扫描电镜对A l/M g 异种金属界面处的IM C 的形 貌和分布进行观察和分析.用扫描电镜能谱分析仪 对Mg /A l 异种金属界面元素成分进行检测和分析， 采用H V -1000B (0. 025 kgf )硬度仪对接头界面处进 行了显微硬度测量，利用拉伸试验机对不同参数下 的试样进行了力学性能测试.图1搅拌摩擦辅助A l/Z n/M g 搭接接头扩散连接示意图Fig. 1 Schematic diagram of Zn powder-assisted diffusionbond of Al/Mg friction stir lop welding2结果及分析2.1 Z n 粉辅助Al /M g 搭接接头宏观形貌镁、铝异种材料搅拌摩擦连接时由于大量Mg -A l 脆性相的产生而影响接头强度，为了改善接头脆 性相的产生，在镁、铝搭接面涂敷一层锌粉，研究其 对接头组织及性能的影响.图2a 、b 、c 分别为旋转速 度为600、800、1 000 r/m in 的A l/M g 搭接接头表 面形貌.图2d 、e 、f 为图2a 、b 、c 对应的界面结合宏 观形貌.1mm(d) 600 r/min图2不同参数下Z n 粉辅助A l/M g 搭接接头表面及其横截面宏观形貌Fig. 2 Macroscopic Morphology of surface andcross-section of Zn powder-assisted Al/Mg FSLW joint under different parameters暋28 •兰州理工大学学报第44卷由图可知，旋转速度在600〜1000r/m in变化 时，A l/M g搭接表面成型良好；界面均出现一白色过渡层.随搅拌针转速的提高，白色过渡层厚度减薄，旋转速度高于1000r/m in时搅拌针轴肩覆盖区白色过渡层消失，该区域涂覆的锌扩散进入铝合金基体中（如图2e、f )而中间Z n粉层由于熔点较 低，随着焊核区热输入逐渐增加使Z n粉液化，在搅 拌针的热剪切、搅拌头的旋转力以及塑化金属的流动作用下一部分进入A l侧焊核区或流入到焊缝表面（如图2b，c方框所示），一部分会沿着搭接层被挤 压出来形成小锌珠（如图2c所示），导致A l/M g搭 接接头界面处Z n扩散层变薄.随转速的提高，界面 过渡层也由平直型（如图2d所示）转化为波浪型（如 图2e所示）可见Z n粉的加入改善了铝、镁的界面 结合状态，且界面的形态随焊接旋转速度的提高发生显著的变化.2.2 Z n粉辅助Al/M g搭接接头界面微观组织图3为图2中各区域的微观组织.图3a为区域 1的放大图，白亮层厚度约为10M m，对点A经电子 探针点扫分析其成分见表1，该层化学成分为大量的Z n以及少量的A l和Mg.进一步放大倍数观察，该白亮层分别为与铝合金、镁合金基体的结合界面.微区4为Z n层与铝合金接触的一侧，该区域组织为 Z n扩散到铝基体构成的固溶体及固溶体中析出的金 属间化合物A lM g n Zn4(颗粒尺寸大约2.5毺m)靠 近Z n层为Zn-M g共晶相及少量伸入铝基体的A lM g2相.与Z n层舭邻的镁侧微观组织如微区5放大(如图3c)所示，该结合界面主要是纤细致密的 M g+M gZ n共晶组织以及少量的未溶化的Z n相 (区域6的F点）锌层与镁基体的界面由于二者晶体结构相同、二者相遇后更易生成金属间化合物，界 面结合良好(如图3d所示）同一参数下，接头界面 不同位置Z n的扩散行为随热输入大小而变化.图3e为区域2的微观组织放大图，该区域不仅Z n扩 散进入A l基体中，大量的M g元素也扩散进入铝基 体中，镁的固溶体与铝的固溶体呈带状交替分布，起 到界面的机械结合的效果.图3f为区域3的放大 图，由于旋转速度的提高使热输入增加，塑化的金属 流动加剧，焊核区温度升高，A l、M g原子的扩散能力以及塑化金属流动性增强，不仅液化的Z n被搅 拌针挤入到A l侧，塑化的A l也进入M g侧呈深灰 色，使得A l、M g直接接触或依靠扩散后能够迅速形 成大量A l-M g系金属间化合物以及A l-Mg-Z n化 合物.图3不同区域的扩散层微观组织形貌Fig. 3 Microstructural morphology of diffusion layer in different areas图4为旋转速度800 r/m in的Z n粉辅助A l/Mg搭接接头扩散层的扫描电镜能谱线扫描分析 结果.在整个扩散层中A l质量分数从A l侧到Mg 侧略呈下降的趋势；M g质量分数在整个扩散层中从镁侧到铝侧呈下降趋势分布，Z n质量分数在整个 扩散层发生跳跃，以Z n层为界限，靠近镁侧的扩散 层中Z n质量分数明显低于靠近铝侧扩散层中Zn 质量分数.分别根据Mg-Zn、A l-Z n二元相图，Z n 在第4期金玉花等：Z n粉辅助Al/M g异种合金搅拌摩擦搭接连接•29暋M g中的最大溶解度为3. 5%，Z n在A l中的最大溶解度为16. 5%.因此涂敷的锌向两侧扩散，两侧的镁、铝也向涂敷的Z n层进行扩散，通过互扩散，铝基体一侧形成A l-Z n固溶体为主的扩散层，镁基体一侧形成Mg-Z n固溶体为主的扩散层，由于搭接焊时铝合金在镁合金的上面，轴肩与铝合金板摩擦产生的热量使得铝合金板温度高于镁合金板，有助于提高Z n在铝基体中扩散速度，导致铝侧的扩散层较镁侧的扩散层厚，在旋转速度为800 r/m in时，铝侧扩散层约为镁侧扩散层的1. 4倍.表1不同区域各点的成分（原子分数）Tab. 1 Compositions at different points in different areas(mass-fraction) %点Al Mg Zn相A 2. 5612.2485. 20富Zn相B30. 1043. 6826. 22AlM gn Zn4C 6. 5458. 8434. 62AlM g2+Mg-Zn 固溶体D 6. 4262. 3732. 21Mg-Zn固溶体E7. 1849. 2643. 65MgZnF30. 843. 7426. 18AlM gn Zn4G52. 437. 0640. 51富 Mg 相H32. 1242. 7225. 16AI5 Mgn Zn4I61 2435. 04 3. 72AI3 Mg2J33. 6561. 22 5. 13AI12 Mgi7图4 Z n粉辅助的A l/M g搭接接头扩散层线扫描Fig. 4 Line scanning of diffusion layer in Zn powder-assisted Al/M g FSLW joint2.3 Z n粉辅助Al/M g搭接接头力学性能分析对焊接旋转速度为800 r/m in工艺下得到的Zn 粉辅助Al/M g搅拌摩擦焊搭接接头进行维氏显微硬 度测量，测量位置依次距离搅拌针中心0、1、2、3 mm，从搭接缝向铝合金、镁合金基体延伸约1.5 mm，硬度 值结果如图5所示.扩散层（约200 M m宽）的显微 硬度要明显高于两侧A l、M g基体的显微硬度；搅拌 针中心处所在截面各点硬度值最大，离搅拌针中心 距离越远，硬度值降低.这是由于在搅拌针中心位置 产生的热量高，在搅拌力以及热量的共同作用下Zn 粉转移导致大量A l-M g系金属间化合物产生，而偏 离搅拌针中心位置处扩散层主要由Mg-Z n的共晶 组织甚至Z n的固溶体构成.Mg-Z n扩散层的显微硬度低于A l-M g扩散层的显微硬度，使基体与扩散 层之间结合强韧性增加，有效地抑制了焊件裂纹萌生与快速扩展.通过对Z n粉辅助的A l/M g搅拌摩 擦焊搭接扩散接头进行拉剪试验，其结果如图6所 示.采用A l/M g直接搅拌摩擦搭接焊，其所能承受 的最大载荷只有3. 24 kN左右，而在界面处涂覆Zn 粉能够使承受的最大载荷达3. 92k N，能使Al/M g 接头抗剪切强度进一步提升.这是因为M g与Z n的晶格类型相同，在界面处生成呈韧脆性的Zn-M g共 晶组织，其脆性要明显低于A l与M g生成的金属间 化合物，提高了界面的结合强度.同时，锌粉的加入 在很大程度上降低了焊接温度，降低了接头的残余 热应力，提高了接头韧性.Z n粉辅助的A l/M g搭接 接头的强度大小依赖于热输入的高低，搅拌针转速 低，扩散层厚，脆性相数量多，强度低.搅拌针旋转速 度提高，Z n容易蒸发，扩散层减薄，Zn-M g共晶组织 的产生降低扩散层的脆性.进一步提高旋转速度，热Fig. 5 Microhardness distribution from weld center of Zn powder-assisted Al/Mg FSLW joints600 800 1 000 1 200 1 400旋转速度/(“min-1)图6不同参数下Z n粉辅助A l/M g搅拌摩擦焊搭接接头断 裂载荷Fig. 6 Failure loads of Zn powder-assisted Al/Mg FSLWjoints with different parameters暋30 •兰州理工大学学报第44卷输入的提高促使Z n扩散进入A l基体，导致界面出现大量A l-M g系化合物，恶化了接头的力学性能.旋转速度为800 r/m in的Z n粉辅助的Al/M g搅拌摩擦搭接接头断裂位置以及断口形貌如图7所示.断裂发生在搭接接头铝基体一侧，断裂面呈韧窝状.镁合金侧断口形貌主要为层流状以及一些解理小平面，小平面两侧有撕裂棱，且M g侧的断裂面上有未完全从基体剥落的颗粒.对比铝侧断裂面，容易找到一些凹坑，这些凹坑尺寸大小与镁侧未剥落的颗粒大小相一致.剪切试验中在剪切力作用下，镁基体中的强化相颗粒从铝基体上脱落下来，表明Zn粉辅助的A l/M g搭接接头对镁合金基体的强化效果高于对铝基体的强化效果.断口特征为韧脆混合型断裂.对A l侧与M g侧的断口进行X R D分析如图8所示，断口两侧X射线衍射结果中均发现金属间化合物A l5Mgn Zn4，M g侧断口处除A l5Mgn Z n外还有A l5Mgn、M gZ n金属间化合物及少量的Zn存在.A l侧断口无其他Mg-Z n化合物.接头断口物相检测的结果进一步解释了断裂面发生在靠近Al(c) Mg侧断口图7接头断口形貌 Fig. 7 Morphology of joint fractureFig. 8 XRD analysis result of joint fracture侧扩散层的原因.3结论1)相比于搅拌摩擦A l/M g搭接连接，夹层敷Z n粉辅助的A l/M g搅拌摩擦焊搭接接头成型性能良好.2) Z n粉辅助A l/M g搅拌摩擦焊搭接接头界面由A l-Z n固溶体，金属间化合物A l5Mgn DZn4以及Mg-Z n共晶区组成，取代了 A l-M g系金属间化合物，只有旋转速度过大时，扩散层出现A l-M g系金属间化合物.3)由于Mg-Zn、A l-Mg-Z n金属间化合物层的出现，扩散层硬度得到提高并具有一定的韧性，使剪切断裂载荷达到3.92k N，断裂发生在铝基体一侧，镁侧断口呈现韧脆混合型断裂.致谢：本文得到甘肃省高等学校基本科研业务费（01-0071)和兰州理工大学博士基金项目（01- 0765)的资助，在此表示感谢.参考文献：[]YAMAMOTO N,LIAO J, WAT A N A BE S,etal. Effect of intermetallic compound layer on tensile strength of dissimilarfriction-stir weld of a high strength Mg alloy and Al alloy [J].第4期金玉花等：Z n 粉辅助A /M g 异种合金搅拌摩擦搭接连接• 31暋Materials Transactions»2009»50(12) ：2833-2838.[]刘政军，宫颖，苏允海.镁铝异种金属TIG 焊接头性能的研 究[].材料工程，2015,43(3):18-22.[3]MOHAMMADI J，BEHNAMIAN Y，MOSTAFAE A，d a/. Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys ： Microstructure studies and mechanical characterizations [J]. Materials Characterization »2015 »101(1)：189-207.[]黄健康，刘宁，何翠翠，等.铝/镀锌钢焊接接头金属间化合物 热力学分析[J].哈尔滨工程大学学报，2016，37(6): 837-841.[5]ZHANG Y ，LUO Z ，LI Y »ei a M icrostructure characterization and tensile properties of Mg/ A 1 dissimilar joints manufactured by thermo-compensated resistance spot welding with Zninterlayer [J]. Materials & Design ，2015,75(6) :166-173.[6] GAO M，MEI S，LI a l .C haracterization and formation mechanism of laser-welded MgandAlAlloysusingTiinter-layer[J]. 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Labspark1000直读光谱仪测定铝合金中Mg、Ni、Ti含量的不确定度评定
100《针量£测试牧木》2019耳第46欺第3輛Labspark1000直读光谱仪测定铝合金中Mg.Ni.Ti含量的不确定度评定黄敏杨洁（自贡检验检测院，四川自贡643000）摘要:本文依据JJG768-2005（发射光谱仪》检定规程，对Labspark1000直读光谱仪测定铝合金中Mg、Ni、Ti元素含量进行了不确定度评定。
关键词：直读光谱仪;铝合金;元素含量;不确定度评定中图分类号：043文献标识码：A国家标准学科分类代码：460.4030D01：10.15988/ki.1004-6941.2019.3.031Evaluation of Uncertainty of Mg、Ni and Ti Contents in Aluminum Alloy by Labspark1000Direct-Reading SpectrometerHuang Min Yang JieAbstract:According to the verification regulation of JJG768-2005Emission Spectrometer,the uncertainty of determination of Mg,Ni and Ti in aluminium alloy by Labspark1000direct reading spectrometer was evaluated. Keywords:direct reading spectrometer；aluminium alloy；element content；uncertainty evaluation1概述钢研纳克开发技术有限公司生产的Labspark1000直读光谱仪用于Fe、Al、Cu、Ni、Co、Mg、Ti、Zn、Pb、Sn、Ag等多种金属及其合金样品分析，分析快速、运行成本低、维护方便、抗干扰能力强,广泛应用于钢铁、铸造、金属回收、冶炼、军工、电力、化工以及高等院校金属加工实验室和质检行业等。
icp-aes测定锌铝镁板镀层中镁、铝、硅、锑的含量
铝标准溶液(1.2.6)100 jxg/mL,由市售标准溶
Mg
285.213
可选径向
液配置；
Al
394.401
可选径向
镁标准溶液(1.2.7)1 000 |ig/mL；
Si
251.611
-
镁标准溶液(1-2.8)100 pcg/mL,由市售标准溶
Sb
231.146
-
液配置；
1.1.2光谱仪的分辨率 测定峰高一半处的峰宽，计算出分辨率,仪器分
积，用ICP - AES测定4个不同厂家的镀锌铝镁板镀层中镁、铝、硅、铸含量。铝的相对标准偏差测定结
果分别为3.34% ,3.74% ,4.20% ,2. 51 % ( n = 11),镀层中铝的回收率为96. 12% - 98. 38%。与常规检
测方法相比,ICP-AES测定法快速、简单、准确率高、精密度好，可满足实际生产样品的分析。 关键词：ICP-AES；镀锌铝镁板；镀层；元素含量
1.3实验步骤 用乙醇将试样表面清洗干净，晾干后称量，样品
在镀层素浓度最高的校准溶液的绝对强度或强
0 引言
随着钢铁材料及涂镀技术的发展，人们对镀层 钢材耐蚀性提出了更高、更苛刻的要求，传统热镀锌 镀层(纯锌镀层)钢材已经不能满足应用要求⑴"。
高耐蚀的 55% Al - Zn、Zn - 5% Al 和 Zn-Al - Mg 合金镀层成为镀层材料发展的重点。尤其是Zn Al - Mg合金镀层，由于具有高耐蚀性和端口耐蚀
Wang Xian , Wang Wenyan
(Technological Center of HBIS Group Tangsteel Company, Tangshan, Hebei, 063000) Abstract: Taking the ethanol as washing solution of sample, the hydrochloric acid solution containing hexa methylenetetramine was used to peel off the coating. The solution was diluted to the specified volume. And the contents of Mg, Al, Si and Sb in the coating of four different manufacturers were determined by ICP AES. The relative standard deviation of aluminum is 3. 34% , 3.74% , 4. 20% , 2.51% (/i = 11 ) , and the recovery of aluminum in the coating is 96. 12% - 98. 38% . Compared with the conventional method, ICP AES is fast, simple, accurate and precise, which can meet the needs of the actual production samples. Key Words： ICP - AES； galvanized aluminum magnesium plate； coating； element content
化学成分对Al—Zn—Mg系模具材料组织和性能的影响分析
化学成分对Al—Zn—Mg系模具材料组织和性能的影响分析对常用的铸造Al-Zn-Mg系合金通过实验研究和金相分析，分析Mg、Zn元素及其它元素对合金的组织和性能的影响，为塑料成型模具材料的选材提供了参考依据。
只有掌握了每种化学元素对合金组织和性能的影响，以及各元素之间的相互作用，才能制出更加符合要求的Al-Zn-Mg系模具材料，发挥铝合金的最大使用性能。
标签：Al-Zn-Mg合金；组织；材料性能；分析近年来，随着工业的高速发展，塑料成型加工量越来越大，在生产中塑料成型模具得到了广泛的运用，并在模具生产中占据了比重较大的地位。
铝合金作为一种应用较早的铸造合金，以其力学性能好，加工性能优良，容易加工与制造，具有表面质量高等优点，成为塑料成型模具优先选用的材料。
研究常用元素对铝合金的组织和性能的影响，使塑料成型模具对合金成分在选材时具有规律可循。
以目前常用的Al-Zn-Mg系铸造铝合金为研究对象，研究Mg、Zn等化学元素对铝合金性能和组织的影响。
1 塑料成型模具的性能要求1.1 具有一定的综合力学性能塑料成型模具材料同其它模具材料一样，应适应工作要求，要具有一定的强度、硬度、塑性、韧性，和一定的耐磨性，同时在工作过程中要承受高温、侵蚀等恶劣工作条件。
1.2 切削加工性好塑料模具形状多变，结构复杂，在模具生产过程中不利于切削加工的实施，切削加工成本常占到模具成本2/3以上，为便于加工，降低成本，模具材料要求具有良好切削性和图案蚀刻性。
1.3 材料具有良好的导热性和低的热膨胀系数。
2 化学成分对Al-Zn-Mg系合金组织的影响2.1 Al-Zn-Mg系铸造铝合金的化学成分Al-Zn-Mg系铸造铝合金以Al元素为主，含有一定的Mg、Zn元素，少量的Cu元素，和微量杂质元素Si和Fe。
2.2 Mg、Zn元素的作用Al-Zn-Mg合金中的Zn、Mg是主要添加合金元素，作为独立组元存在时，Zn 和Mg在Al中的溶解度较高，Zn固溶在Al基体中，起到固溶强化作用，Zn使合金保持适度的耐磨性和润滑性，Zn含量过低，合金的耐磨性和抗咬合性能差；Zn含量过高时，韧性变差，加大了应力腐蚀的倾向。
晶粒组织对7020-T5铝合金型材强度和抗腐蚀性能的影响
第 54 卷第 7 期2023 年 7 月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.54 No.7Jul. 2023晶粒组织对7020-T5铝合金型材强度和抗腐蚀性能的影响柯彬1，叶凌英1, 2，王鹏宇1，刘晓东1，董宇1，张勇1, 2，唐建国1, 2，刘胜胆1, 2(1. 中南大学 材料科学与工程学院，湖南 长沙，410083；2. 中南大学 教育部有色金属材料和工程重点实验室，湖南 长沙，410083)摘要：通过室温拉伸试验、剥落腐蚀试验、慢应变速率拉伸试验和四点弯曲试验，并结合金相观察、电子背散射衍射(EBSD)和透射电镜(TEM)等微观组织分析技术，研究晶粒组织对7020-T5铝合金型材的强度、抗剥落腐蚀性能以及抗应力腐蚀性能的影响。
研究结果表明：完全再结晶型材的室温拉伸强度较低，其抗剥落腐蚀性能达到N 级，但型材的抗应力腐蚀性能严重恶化，应力腐蚀敏感指数I SSRT 为9.55%，四点弯曲试验中应力腐蚀裂纹沿着再结晶晶粒向内快速扩展，24 h 即发生应力腐蚀断裂。
表层粗晶和内部再结晶晶粒降低材料的力学性能，使应力腐蚀裂纹在型材表面深度方向上的扩展速率加快。
晶粒细小、不含表层粗晶、再结晶分数低的均匀变形组织有利于获得更高的综合性能，具有该种晶粒组织的7020-T5铝合金型材的抗拉强度和屈服强度分别达到366.6 MPa 和314.2 MPa ，断后伸长率达到15.7%，抗剥落腐蚀性能达到PB 级，应力腐蚀敏感指数I SSRT 为2.38%，四点弯曲应力腐蚀试验中表面产生腐蚀裂纹和发生应力腐蚀断裂的时间分别为580 h 和1 736 h ，抗应力腐蚀性能优异。
关键词：Al-Zn-Mg 铝合金；晶粒组织；再结晶；剥落腐蚀；应力腐蚀中图分类号：TG146.2 文献标志码：A 文章编号：1672-7207（2023）07-2618-12Effect of grain structures on strength and corrosion resistance of7020-T5 aluminum alloy profilesKE Bin 1, YE Lingying 1, 2, WANG Pengyu 1, LIU Xiaodong 1, DONG Yu 1,ZHANG Yong 1, 2, TANG Jianguo 1, 2, LIU Shengdan 1, 2(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central SouthUniversity, Changsha 410083, China)Abstract: The effect of grain structures on the strength and corrosion resistance 7020-T5 alloy profiles was studied through tensile test, exfoliation corrosion test(EXCO), slow strain rate tensile test(SSRT) and four-point收稿日期： 2022 −09 −09； 修回日期： 2022 −11 −05基金项目(Foundation item)：国家重点研发计划项目(2016YFB0300901) (Project(2016YFB0300901) supported by the National KeyResearch and Development Program of China)通信作者：叶凌英，博士，教授，从事高性能铝合金材料加工制备研究；E-mail ：******************.cnDOI: 10.11817/j.issn.1672-7207.2023.07.009引用格式： 柯彬, 叶凌英, 王鹏宇, 等. 晶粒组织对7020-T5铝合金型材强度和抗腐蚀性能的影响[J]. 中南大学学报(自然科学版), 2023, 54(7): 2618−2629.Citation: KE Bin, YE Lingying, WANG Pengyu, et al. Effect of grain structures on strength and corrosion resistance of 7020-T5 aluminum alloy profiles[J]. Journal of Central South University(Science and Technology), 2023, 54(7): 2618−2629.第 7 期柯彬，等：晶粒组织对7020-T5铝合金型材强度和抗腐蚀性能的影响bending test, combined with microstructure analysis such as optical microscope(OM), electron backscatterdiffraction(EBSD) and transmission electron microscopy(TEM). The results show that the tensile strength of the fully recrystallized profile is remarkably low, and the EXCO resistance reaches N grade, but its stress corrosion resistance is seriously deteriorated, the stress corrosion cracking sensitivity index ISSRTis 9.55%, and the stress corrosion crack propagates rapidly along the recrystallized grains in the four-point bending test, and fracture occurs within 24 h. Coarse grain layers on the surface and internal recrystallized grains decrease the mechanical properties, and accelerate the propagation rate of stress corrosion cracks in the depth direction. Uniform deformed microstructures with small grains, and no surface coarse grain layers and low recrystallization fraction favor to obtain higher comprehensive properties. The tensile strength and yield strength of 7020-T5 alloy profile with this grain structure reaches 366.6 MPa and 314.2 MPa, respectively, the elongation after fracture reaches 15.7%, theEXCO resistance reaches PB level, the ISSRTis 2.38%, the time of the corrosion crack appeared on surface and fractured by stress corrosion cracking(SCC) in the four-point bending stress corrosion test are 580 h and 1 736 h, respectively, showing excellent stress corrosion resistance.Key words: Al-Zn-Mg aluminum alloys; grain structures; recrystallization; exfoliation corrosion test; stress corrosion resistance7020铝合金作为典型的Al-Zn-Mg合金，因为具有高比强度、良好的成型性能和焊接性能，在航空航天、轨道交通上获得了广泛地应用[1−3]。
alznmg合金电子理论研究
攘簧３＋对Ａ１一Ｚｎ－Ｍｇ燕合金固溶体中可戆的ＡＩ－Ｚｎ，ＡＩ—Ｍｇ及Ｍｇ－Ｚｎ二元缡蘩晶舞墓翔Ａ１一Ｚｎ－Ｉｖｌｇ三元缡聚鑫齄麴徐毫孚皱褥避褥计萁，分糈了该合金中玎‘、，７＇／／出桕的结构模戮。
４，辩Ａ１－Ｚｎ系禽金过饱和嗣溶体在时效过程审脱滚的Ｇ．Ｐ逐蒜母摇的界面能做了计算，并对英界霹的匿电荷密度进行计黧。
关键谲：Ａｌ—Ｚｎ．Ｍｇ繇合金ＥＥＴ堙论＋价电子结构界面能＋本文为国撤自然科学基盒资助课题（５００６１００１）广话大学硬：｝学位论文ＴＨＥＳＴＵＤＹＯＦＡｔ－Ｚｎ—ＭｇＡＬＬＯＹＳＷｌＴ鞋ＥＬＥＣＴＲＯＮＴＨＥＯＲＹＡＢＳＴ＆ＡＣ下ＡＩ＊Ｚｎ－ＭｇＡｌｌｏｙｓｐｌａｙｅｄａｌｌｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｔｈｅａｖｉｇａｔｉｏｎａｎｄａｎｄｐｒｅｆｅｒａｂｌｅａｇｅｈａｒｄｎｅｓｓ．ｓｐａｃｅｆｌｉｇｈｔｄｕｅｔｏｔｈｅｉｒｌｏｗｄｅｎｓｉｔｙ，ｈｉｇｈｓｔｒｅｎｇｔｈＯｎｅｄｒａｗｂａｃｋｏｆｔｈｅｓｅａｌｌｏｙｓⅥ髓ｔｈｅｉｒｓｕｓｃｅｐｔｉｂｉｌｉｔｙｔｏｓｔｒｅｓｓｃｏｒｒｏｓｉｏｎｃｒａｃｋｉｎｇ（ＳＣＣ）。
Ａｌｔｈｏｕｇｈｏｖｅｒａｇｉｎｇｐｒｏｃｅｓｓｅｓｃｏｕｌｄｉｍｐｒｏｖｅｔｈｅｐｅｒｆｏｒｍａｎｃｅｏｆｒｅｓｉｓｔａｎｃｅｔｏｓｔｒｅｓｓｃｏｒｒｏｓｉｏｎｃｒａｃｋｉｎｇ，ｉｔｃｏｕｌｄｒｅｄｕｃｅｔｈｅａｌｌｏｙｓ’ｓｔｒｅｎｇｔｈｓｉｍｕｌｔａｎｅｏｕｓｌｙ．Ｔｈｅｓｔｕｄｙｏｆｔｈｅｍｉｃｒｏｃｏｓｍｉｃｍｅｃｈａｎｉｓｍｂｅｔｗｅｅｎｓｔｒｕｃｔｕｒｅａｎｄｐｅｒｆｏｒｍａｎｃｅｓｗａｓｏｆｇｒｅａｔｉｍｐｏｒｔａｎｃｅ遮ｏｒｄｅｒｔｏｋｅｅｐｔｈｅａｌｌｏｙｓ’ｐｒｏｇｒｅｓｓｉｖｅｓｔｒｅｓｓｃｏｒｒｏｓｉｏｎｃｒａｃｋｉｎｇｔｏｇｅｔｈｅｒｗｉｔｈｔｈｅｉｒｈｉｇｈ—ｓｔｒｅｎｇｔｈａｆｔｅｒａｐｐｒｏｐｒｉａｔｅｈｅａｔｔｒｅａｔｎｌｅｎｔ．ＵｎｆｏｒｔｕｎａｔｅｌｙｄｕｓｔｖｅｒｙｌｉｍｉｔｅｄｗｏｒｋｈａｓｂｅｅｎｄｏｎｅＯｎｓｔｕｄｙｉｎｇｔｈｅｍｉｃｒｏｃｏｓｍｉｃｍｅｃｈａｎｉｓｍｂｅｔｗｅｅｎｔｈｅｓｔｒｕｃｔｕｒｅａｎｄｐｅｒｆｏｒｍａｎｃｅｓ．确ｅｖａｌｅｎｃｅｅｌｅｃｔｒｏｎｓｔｒｕｃｔｕｒｅｓａｎｄｉｎｔｅｒｐｈａｓｅｐｅｒｆｏｒｍａｎｃｅｓｏｆｅａｃｈｓｏｌｉｄｓｏｌｕｔｉｏｎａｎｄｐａｒｔｏｆｔｈｅｐｒｅｃｉｐｉｔａｔｉｏｎｓｉｎＡ１一ＺｎａｎｄＡ１－Ｚｎ－－ＭｇａｌｌｏｙｓｖｃｅｒｅａｎａｌｙｚｅｄｓｙｓｔｅｍａｔｉｃａｌｌｙａｃｃｏｒｄｉｎｇｔｏｔｈｅＥｍｐｉｒｉｃａｌＥｌｅｃｔｒｏｎｉｃＴｈｅｏｒｙｉｎｓｏｌｉｄａｎｄｍｏｌｅｃｕｌｅｓ（ＥＥＴ）ａｎｄｉｍｐｒｏｖｅｄＴＦＤｍｅｔｈｏｄｂｙＣｈｅｎｇＫａｉｊｉａ。
锌合金压铸件电镀前的质量要求
锌合金压铸件电镀前的质量要求英文回答：Quality Requirements for Zinc Alloy Die Casting before Electroplating.Zinc alloy die castings are widely used in various industrial applications due to their excellent mechanical properties, dimensional accuracy, and cost-effectiveness. Electroplating is a common surface treatment technique applied to zinc alloy die castings to enhance their corrosion resistance, wear resistance, and aesthetic appeal. However, the quality of the electroplated finish is highly dependent on the quality of the substrate, which is thezinc alloy die casting. To ensure a successfulelectroplating process, it is crucial to adhere to specific quality requirements for the zinc alloy die castings priorto electroplating.Surface Quality: The surface of the zinc alloy diecasting should be smooth and free of any defects, such as burrs, scratches, or pits. Any imperfections on the surface can create weak spots in the electroplated coating, leading to premature failure. Therefore, it is essential to carefully inspect the die castings for any surface imperfections and remove them using appropriate methods, such as polishing or grinding.Dimensional Accuracy: The dimensional accuracy of the zinc alloy die casting is another important factor that affects the quality of the electroplated finish. Excessive dimensional variations can make it difficult to achieve a uniform electroplated coating, resulting in uneven thickness or gaps in the coating. It is crucial to ensure that the dimensions of the die casting are within the specified tolerances to facilitate a successful electroplating process.Chemical Composition: The chemical composition of the zinc alloy die casting plays a vital role in determiningits suitability for electroplating. Zinc alloys typically contain various alloying elements, such as aluminum,magnesium, and copper, to enhance their mechanical properties. However, these alloying elements can alsoaffect the electroplating process. For example, high levels of aluminum can lead to the formation of an unstable intermetallic layer between the zinc alloy and the electroplated coating, compromising its adhesion. Therefore, it is important to control the chemical composition of the zinc alloy die casting to ensure compatibility with the electroplating process.Cleanliness: The surface of the zinc alloy die casting should be thoroughly cleaned prior to electroplating to remove any dirt, grease, or other contaminants. These contaminants can act as barriers between the zinc alloy and the electroplated coating, preventing proper adhesion. Therefore, it is essential to use appropriate cleaning methods, such as ultrasonic cleaning or solvent degreasing, to ensure that the surface of the die casting is free from any contaminants.Conclusion: Adhering to these quality requirements for zinc alloy die castings prior to electroplating is crucialto ensure a successful electroplating process. By carefully inspecting and preparing the die castings, it is possible to achieve a high-quality electroplated finish that meets the desired performance and aesthetic requirements.中文回答：锌合金压铸件电镀前的质量要求。
变形镁锂超轻合金研究镁锂合金MgLi合金超轻镁锂合金
图 1 镁合金压铸件
3
• 镁锂合金则是目前最轻的金属结构材料，比普通镁合金轻 1/4-1/3，比铝合金轻1/3-1/2所以镁锂合金故又被称为超轻 合金，由于金属锂可以与镁形成立方结构的β相，使镁合 金获得具有良好的塑性、比强度和比刚度在汽车、3C、航 空、航天等领域具有较好的应用前景
图 2 变形镁锂合金
89Biblioteka 图 3 宇航领域应用4
2、实验过程
5
实验过程
• 研究内容
• 由于Mg-Li合金化学性质活泼，熔炼条件要求较高，限制 了它的应用，本次研究拟进行合金成分设计、铸造工艺、 挤压工艺和轧制工艺等措施，成功生产出相对密度1.5，
强度200MPa以上的Mg-Li合金板材； • 试验方法
• 采用真空熔炼方式获得MgLi9RE、MgLi16RE和MgLi45RE 铸锭，经过均匀化退火之后，分别挤压成60×6mm的板 材，在此基础上继续进行轧制，最终得到厚度为0.5mm的 薄板。通过DTA、XRD、SEM分析以及显微硬度、金相 观察等分析所得合金试样的各方面性能。
内容
1、应用背景 2、实验过程 3、结论
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1、应用背景
2
应用背景
镁合金是继钢铁和铝合金之后发展起来的第三类金属结 构材料，按成型工艺可分为铸造镁合金和变形镁合金。目 前比较常见的镁合金材料大部分是压铸工艺生产的铸造镁 合金，主要应用于汽车零件和机件壳罩等构件（如图1所 示）；由于镁合金晶体结构为密排六方造成其变形困难且 容易开裂，因此研究变形镁合金的成型性能，对于提高镁 合金的推广和应用具有重要的意义。
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图 4 镁锂合金铸锭
图 5 可浮于水面的MgLi45合金铸锭
图4为浇注成型的镁锂合金铸锭，图5为MgLi45合金，由于 合金中含有大量金属锂，合金密度迅速下降，整块铸锭 可完全漂浮于水面上。
Al、Zn、Cd对MG-Li合金界面结构及性能影响的第一性原理研究的开题报告
Al、Zn、Cd对MG-Li合金界面结构及性能影响的
第一性原理研究的开题报告
研究背景
MG-Li合金具有密度低、强度高等优良性能，在航空、航天及汽车等领域有着广泛的应用前景。
然而，当碱金属Li溶于MG基体中时，易出现与其他杂质元素的反应，从而引起合金的界面结构和性能的变化。
其中Al、Zn、Cd等元素常常作为合金中的杂质元素存在，影响了MG-Li合金的性能表现。
因此，了解这些杂质元素对于MG-Li合金的影响，对其更好的设计和应用具有重要意义。
研究目的
本文旨在通过第一性原理研究方法，探究杂质元素Al、Zn、Cd对MG-Li合金界面结构和性能的影响机理。
具体目的包括：
1. 分析Al、Zn、Cd等元素与MG-Li合金界面的化学反应机理以及元素间的互相影响。
2. 探究元素掺杂对MG-Li合金原子结构和晶体性质的影响。
3. 分析元素掺杂对MG-Li合金电子结构和物理性质的影响。
研究方法
本文将基于第一性原理计算方法，采用材料计算软件VASP、Quantum Espresso等计算软件，对MG-Li合金及其与杂质元素Al、Zn、Cd之间界面的原子结构、电子结构和物理性质进行建模和计算分析。
预期结果
本文将通过模拟计算得到MG-Li合金与不同杂质元素Al、Zn、Cd界面的原子结构、电子结构、物理性质等参数，分析这些元素的掺杂对MG-Li合金性能的影响机理。
预期结果将有助于深入了解MG-Li合金中杂
质元素的掺杂行为和其对合金性能的影响，从而为其应用开发和材料改良提供科学依据。
Mg-Zn-Al基镁合金组织和性能的研究的开题报告
Mg-Zn-Al基镁合金组织和性能的研究的开题报告一、研究背景和意义镁合金作为轻量化材料，近年来受到越来越多的关注和研究。
由于其具有低密度、高比强度和良好的可回收性等优异性能，广泛应用于航空、汽车、船舶、电子等领域。
Mg-Zn-Al基镁合金是一种重要的镁合金，具有良好的塑性和韧性，适合用于制造各种结构件和零件。
然而，Mg-Zn-Al基镁合金在使用过程中存在一些问题，如易产生孔洞和裂纹、易氧化和腐蚀、力学性能差等。
因此，需要对Mg-Zn-Al基镁合金进行相关研究，以改善其组织和性能，提高其应用价值和推广应用。
二、研究内容和方法（一）研究内容1.分析Mg-Zn-Al基镁合金的组织结构特点和缺陷问题，探究其形成机理。
2.采用不同的制备工艺（如熔铸、等静压、挤压等方法）制备Mg-Zn-Al基镁合金试样，探究各种工艺条件对合金组织和性能的影响。
3.分析Mg-Zn-Al基镁合金试样的力学性能、腐蚀性能和耐热性能，并对其进行比较分析。
（二）研究方法1.采用金相显微镜和扫描电子显微镜等方法，对Mg-Zn-Al基镁合金试样的组织结构进行分析和观察。
2.使用万能试验机和冲击试验机等设备，测试合金试样的力学性能，并分析各种工艺条件对力学性能的影响。
3.采用盐雾试验、腐蚀性能测试和高温氧化实验等方法，评价合金试样的腐蚀性能和耐热性能。
三、预期结果和意义通过研究Mg-Zn-Al基镁合金的组织和性能，可以得出以下预期结果：1.分析Mg-Zn-Al基镁合金的组织结构和缺陷问题，探究其形成机理，为后续研究提供基础。
2.通过比较分析不同工艺条件下合金试样的组织和性能，得出较优的制备工艺参数，为制备高性能的Mg-Zn-Al基镁合金提供技术支持。
3.评价Mg-Zn-Al基镁合金试样的腐蚀性能和耐热性能，并对其进行比较分析，为合金的应用推广提供参考。
本研究对Mg-Zn-Al基镁合金的组织和性能进行系统研究，具有重要的理论和应用价值，对推动镁合金材料的发展，构建低碳、环保的社会经济环境具有重要的意义。
Ag、Y、Gd掺杂体系的Mg-Li-Al-Zn合金的微观结构及性能研究的开题报告
Ag、Y、Gd掺杂体系的Mg-Li-Al-Zn合金的微观结构及性能研究的开题报告1. 研究背景Magnesium (Mg) alloys are considered as one of the most promising lightweight structural materials due to their low density, high specific strength, and excellent corrosion resistance. However, the poorductility, limited strength, and low creep resistance of Mg alloys limit their industrial applications. Alloying with other elements can improve the mechanical and physical properties of Mg alloys. Among these elements, Al, Li, Zn, and rare earth (RE) elements have attracted much attention due to their high solubility in Mg and their positive effect on the properties of Mg alloys.AG, Y, and Gd are common rare earth elements that have high atomic numbers and large ionic radii. These elements are expected to have significant solid solution strengthening effects in Mg alloys. Nevertheless, their interaction with other elements and their effect on the microstructure and properties of Mg alloys are not fully understood. This study aims to investigate the microstructure and properties of Mg-Li-Al-Zn alloys doped with AG, Y, and Gd.2. 研究内容和方法The proposed research will focus on the following aspects:2.1. Alloy synthesis and characterizationMg-Li-Al-Zn alloys doped with AG, Y, and Gd with different concentrations will be prepared using a gravity casting method. The as-cast alloys will be subjected to microstructural and chemical characterizations, including optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction.2.2. Mechanical properties testingThe tensile and compression strengths, ductility, and fatigue resistance of the alloys will be evaluated through mechanical testing. Tensile samples will be prepared according to ASTM standards, and the tensile testing will be carried out using a servo-hydraulic testing machine. The compression testing will be performed using acompressive testing machine, while the fatigue testing will be carried out using a fatigue testing machine.2.3. Microstructure and properties correlationThe microstructure-property correlation of the alloys will beestablished based on the results of the microstructural and mechanicalcharacterizations. The effect of AG, Y, and Gd on the microstructureand properties of Mg-Li-Al-Zn alloys will be analyzed and discussed.3. 研究意义和创新点This study will provide valuable insights into the effect of AG, Y, and Gd on the microstructure and properties of Mg-Li-Al-Zn alloys. The correlation between the microstructure and properties of the alloys willbe established, which can help researchers and engineers to design andoptimize new Mg alloys. The study will also contribute to thedevelopment of new lightweight structural materials for variousapplications, such as aerospace, automotive, and biomedical industries.The main innovation of this research is to investigate the effect ofAG, Y, and Gd on the properties of Mg-Li-Al-Zn alloys. The study willprovide a systematic understanding of the interaction between theserare earth elements and other alloying elements in Mg alloys, which canhelp to develop new alloys with improved properties.。
Mg-Zn-Al新型镁合金开发及半固态触变成形的开题报告
Mg-Zn-Al新型镁合金开发及半固态触变成形的开题报告一、研究背景及意义镁合金是轻质的金属材料，具有良好的可塑性、高比强度和良好的热导性能等优点，因此在航空航天、汽车工业、电子器件等领域得到了广泛的应用。
随着科技的进步和经济的发展，镁合金的需求量越来越大。
而在镁合金中，Mg-Zn-Al系列合金是一种新型的镁合金，具有高强度、较好的耐腐蚀性和较高的塑性等优点，因此受到了广泛的关注。
半固态触变成形是一种新兴的金属成形技术，能够在较低的温度下实现高精度、高质量、高效率的金属零件制造，具有很高的应用前景。
而Mg-Zn-Al系列合金在半固态触变成形中具有很大的潜力。
因此，开展Mg-Zn-Al新型镁合金的研究，探究其在半固态触变成形中的应用，具有十分重要的研究意义。
二、研究内容及技术路线本文的研究内容主要包括以下几个方面：1. Mg-Zn-Al新型镁合金的制备：选择合适的原料，采用熔铸、挤压等方法制备Mg-Zn-Al合金，并对合金进行组织结构和成分分析。
2. Mg-Zn-Al新型镁合金的力学性能测试：通过拉伸、压缩等试验，测试Mg-Zn-Al新型镁合金的力学性能，包括屈服强度、延伸率、断裂强度等参数。
3. 半固态触变成形工艺研究：首先确定半固态触变成形的工艺参数，包括温度、应变速率等；然后利用实验验证Mg-Zn-Al新型镁合金在半固态触变成形中的可行性，并分析影响成形质量及产品性能的因素。
4. 复合成形技术研究：将半固态触变成形技术与其他成形技术结合，如注射成形技术、挤压成形技术等，形成多种复合成形技术，并对其进行比较分析。
技术路线如下：三、预期研究成果1. 成功制备出Mg-Zn-Al新型镁合金，并对其组织结构和成分进行了分析。
2. 测试出Mg-Zn-Al新型镁合金在拉伸、压缩等试验中的力学性能。
3. 确定了Mg-Zn-Al新型镁合金在半固态触变成形中的工艺参数，并对其成形性能进行了分析。
4. 研究出了Mg-Zn-Al新型镁合金的多种复合成形技术，并进行了比较分析。
Al--Zn--Mg--Cu合金析出相的电子显微学研究的开题报告
Al--Zn--Mg--Cu合金析出相的电子显微学研究的开题报告研究背景：Al--Zn--Mg--Cu合金是一种先进的高强铝合金，在航空航天、交通运输、轻工业等领域有广泛的应用。
该合金具有优异的力学性能、疲劳性能和耐腐蚀性能，在提高航空器及轨道交通运输工具的性能和降低燃料消耗方面具有重要的应用价值。
合金中的析出相对其性能和应用具有重要的影响，因此对Al--Zn--Mg--Cu合金析出相的研究具有重要的学术意义和实际应用价值。
电子显微学技术是一种有效的材料表征手段，已经在合金中析出相的研究中得到广泛应用。
该方法通过细微结构的表征，可以揭示合金中的析出相的组成、形貌、位置等信息，为进一步优化合金制备工艺，提高性能提供理论基础。
研究内容和目的：本研究旨在通过电子显微学技术对Al--Zn--Mg--Cu合金中的析出相进行表征，研究其形貌、组成、位置等。
具体研究内容如下：1. 采集Al--Zn--Mg--Cu合金析出相的电子显微图像。
2. 对采集的电子显微图像进行处理，分析合金中析出相的组成成分。
3. 分析合金中析出相的形貌、位置等微观结构特征，揭示Al--Zn--Mg--Cu合金中析出相的基本形成规律。
4. 结合力学性能测试等方法，研究Al--Zn--Mg--Cu合金中析出相的性能影响机制。
本研究的目的是揭示Al--Zn--Mg--Cu合金中析出相的形成规律和性能影响机制，为进一步优化合金制备工艺，提高性能提供理论基础。
研究方法：本研究主要采用以下电子显微学技术：1. 扫描电子显微镜（SEM）：用于获得高分辨率的断口表面形貌图像。
2. 透射电子显微镜（TEM）：用于获得高分辨率的析出相晶体学结构图像。
3. X射线衍射（XRD）：用于确定析出相的晶体相结构和组成。
同时，本研究将结合力学性能测试等方法，探究析出相的性能影响机制。
预期成果：通过对Al--Zn--Mg--Cu合金析出相的电子显微学研究，预计达到以下成果：1. 确定合金中析出相的组成成分。
Al-Zn-Mg(Cu)合金的热处理、微观结构与性能研究的开题报告
Al-Zn-Mg(Cu)合金的热处理、微观结构与性能研究的开题报告一、研究背景及意义随着工业化的发展，航空航天、交通运输、建筑等领域对高强度、轻量化、耐腐蚀的材料需求越来越高，而铝合金作为一种优良的轻质结构材料，应用广泛，其中Al-Zn-Mg(Cu)合金因其良好的综合性能，成为研究的热点。
但是，该合金在加工过程中由于晶粒细化、析出相形态、分布等因素的影响，容易产生一系列的变形和力学性能损失的问题，因此需要对其进行热处理，提高其综合性能。
本论文的意义在于，通过热处理方式的选择和控制，研究Al-Zn-Mg(Cu)合金的微观结构与性能变化关系，为其合理应用和工业化生产提供科学依据。
二、研究内容及方法本研究将以Al-Zn-Mg(Cu)合金为研究对象，通过不同的加热温度、时间和冷却方式对其进行热处理，并采用光学显微镜、扫描电镜、X射线衍射仪、差热分析仪等测试手段，研究热处理对合金中晶粒细化、析出相形态与分布、硬度、拉伸强度、屈服强度等力学性能的影响。
具体研究内容包括：1.利用T6和T7两种常用的热处理工艺对合金进行处理，并比较其差异性；2.探究不同热处理参数（加热温度、时间、冷却方式）对合金性能的影响；3.分析热处理后合金的微观结构变化，如晶粒细化、析出相形态与分布等；4.分析热处理后合金的力学性能变化，如硬度、拉伸强度、屈服强度等。
三、预期结果及创新点通过本研究，预计可以得到以下的结果：1.热处理工艺对Al-Zn-Mg(Cu)合金的微观结构和力学性能有显著影响；2.合理选择和控制热处理参数可以有效改善合金的综合性能，提高其在工业应用中的使用价值；3.研究结果对该合金的热处理技术和应用具有一定的参考意义。
本研究的创新点在于，通过对Al-Zn-Mg(Cu)合金的微观结构及其与力学性能的关系进行研究，并探究合理热处理工艺参数对其的影响，为该合金的精细化生产和应用提供了理论和实践基础。
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JMEPEG(2001)10:596–601᭧ASM International Evaluation of an Al-Zn-Mg-Li Alloy/Potential Candidateas Al-Sacrificial AnodeS.Valdez,J.Genesca,B.Mena,and J.A.Juarez-Islas(Submitted22March2000;in revised form5June2000)This paper forms part of an overall effort to develop Al-sacrificial In/Hg free anodes;our research hasbeen directed toward developing Al alloys appropriate for cathodic protection.The Al-Zn-Mg system hasbeen particularly selected due to the presence of precipitates in the␣-Al matrix,which are capable ofbreaking down passive films while presenting good electrochemical efficiencies.At the same time,the effectof Li additions on superficial activation of the anode by means of precipitation of AlLi-type compoundswas examined.The microstructure was characterized in the as-cast and as-aged ingots,showing the presenceof␣-Al dendrites as well as eutectic of Al2Mg3Zn3and precipitates of Mg7Zn3in interdendritic regions.Electron microscopic observations performed on specimens with and without heat treatments showed inthe␣-Al matrix the presence of a uniform distribution of precipitates of(-Al2Zn3Mg3,Mg7Zn3,and␦-AlLi type.The electrochemical behavior of the alloy was investigated in a3%NaCl solution simulatingseawater at room temperature.After evaluation of the electrochemical efficiency,values up to67%wereobtained.The relationship between microstructure and electrochemical efficiency is discussed in this workand suggestions of future research are given in order to improve the electrochemical behavior of Al anodesin the field.to environmental protection.Particularly,the use of In alone Keywords Al-sacrificial anodes,electrochemical efficiency,or coupled with Hg in Al alloys during dissolution results in microstructure,precipitatessea life pollution and gives rise to great environmental issues.In order to avoid sea life pollution due to elements such as Hg 1.Introductionand In,and at the same time provide an Al alloy adequate forcathodic protection application,the Al-Zn-Mg system has been Presently,the most commonly used sacrificial metals for investigated in terms of distribution of intermetallics in the␣-cathodic protection systems are alloys of Mg,Zn,and Al.Al matrix capable of breaking down passive films as well The Al anodes are keenly related to alloy chemistry and to as presenting good electrochemical efficiencies.[3]Regarding environmental application.Aluminum has attained considerable electrochemical efficiency or anode current capacity,this should merit as the basis for a galvanic anode mainly due to its lowbe expressed in A-h/kg(where A-h is ampere-hour)and density,large electrochemical equivalent,availability,and rea-represents a figure of the effectiveness of the anode alloy.The sonable cost.The low electrode potentials of Al anodes areelectrochemical capacity is often expressed as percent of readily adaptable to a variety of saline environments such asefficiency.seawater,marine muds,and brackish waters.Unalloyed AlFor instance,it has been reported,[4]in the as-cast condition, adopts a relatively noble solution potential in saline media asthe existence of a microstructure consisting of␣-Al solid solu-a result of its protective oxide film.The oxide is the cause oftion with precipitation of thephase and a eutectic consisting rapid polarization when aluminum is placed under a corrosionof a fine dispersion of the␣ϩsegregated at grain boundaries. load in a cathodic protection circuit.Nevertheless,the successFurther dispersion of thephase in the matrix has been of the Al anode depends upon the alloying of certain metalsincreased by means of thermal treatments applied to as-cast whose surface role is to ultimately prevent the formation of aingots,by taking advantage of the fast kinetic reactions taking continuous,adherent,and protective oxide film on the alloy,place in solid state at400ЊC,giving as a result Al anodes with thus permitting continuous galvanic activity of the aluminum.electrochemical efficiencies up to78%.[5]Research carried out toward the development of Al alloys appro-This research has as its main scope to identify the possibility priate for cathodic protection has considered the influence ofalloying elements such as Zn,Ti,Hg,and In.[1,2]The use of each of the substitution of Al-Zn-In and Al-Zn-In-Hg sacrificial of those elements has shown an improvement of Al activation in anodes,by alloys of the Al-Zn-Mg type,in order to avoid sea neutral chloride media.However,the seemingly good results life pollution without decreasing the current efficiency of the obtained in this field are in contrast with the increased sensitivity resulting anodes.The first part of this research was focused onthe identification and distribution of precipitates in the Al alloy,in order to achieve two targets:the first one is to obtain a good S.Valdez,B.Mena,and J.A.Juarez-Islas,Instituto de Investigaciones surface activation of the anode and the second to yield corrosion en Materiales-UNAM,Circuito Escolar S/N,Cd.Universitaria,04510,products similar to those found in seawater in order to avoid Mexico,D.F.Mexico;and J.Genesca,Fac.de Quimica,Depto depollution of sea life.As a first step,reference was made of Metalurgia-UNAM,Circuito Escolar S/N,Cd.Universitaria.Contacte-mail:julioalb@servidor.unam.mx.the work of Barbucci[5]producing Al-Zn-Mg alloys but withadditions of Li.The resulting microstructure was then character-ized,with particular attention paid to identification of precipi-tates in the␣-Al matrix and eutectics in interdendritic regions,in both as-cast ingot and aged samples.The research was alsodirected toward the effect of Li additions on superficial activa-tion of the anode by means of precipitation of the␦-AlLiintermetallic at grain boundaries and/or matrix,and by takingadvantage of the fact that the Zn decreases the solid solubilityof Li in the␣-Al phase.[6]2.Experimental ProcedureAn Al-5at.%Zn-5at.%Mg-0.1at.%Li alloy was preparedwith commercially available Al,Zn,and Mg with purities of99.98%.The Li was used as a wire of3.2mm in diameter Fig.1As-cast microstructure of the Al-Zn-Mg ingotand99.9%of purity with4.5mg/cm of Na.Due to previousexperiences during melting of these kinds of alloys and in orderto avoid losses of Mg,Zn,and Li,these elements were placedin Al capsules.Initially,the Al was placed in an alumina/graphite coated crucible and melted in a resistance furnaceunder an argon atmosphere.Once the Al was melted,the liquidbath was overheated150ЊC and the Al capsules containing Znand Mg were added.The bath was stirred with argon for10minin order to have uniform distribution of Zn and Mg.Immediatelyafter this operation,the Al capsule containing Li was added tothe liquid bath,which was stirred with a flux of argon foranother5min after which the liquid alloy was poured into acopper mold of dimensions8ϫ8ϫ50cm.The top and bottomof the ingot were cut off for chemical analysis,giving a nominalcomposition of Al-4.8at.%Zn-5.1at.%Mg and0.09at.%Li.In order to perform the characterization of the resultingmicrostructure,the ingots were sectioned transversally to theFig.2Microstructure observed in samples aged at400ЊC(5h).Inset heat flow,ground,polished,and etched in Keller’s reagent toshows the coarsening and growth of the spherical particles aligned as reveal the different phases,precipitates,and/or intermetallicrows in the eutecticcompounds present in the ingot.Aged treatments were per-formed in the as-cast ingot in order to enhance precipitation,following the aging steps(1)aging at400ЊC for5h and(2)aging at400ЊC for5h with an additional heating of160ЊCfor2h.The resulting microstructure was characterized usinga Stereoscan440scanning electron microscope(SEM,LeicaElectron Optics,England)and a2100Jeol scanning transmis-sion electron microscope(STEM,Japan Electron Optics,Tokyo).Both electron microscopes were equipped with wave-length dispersive x-ray(WDX)microanalyses facilities.X-raydiffractometry on aluminum samples in all conditions was per-formed using a Siemens5000x-ray diffractometer with Cu K␣radiation,a Ni filter,and a scan velocity of2Њ/min.A laboratory procedure was carried out for determining thecurrent capacity characteristics of the new aluminum alloy.Asample of dimensions1ϫ1ϫ0.2cm of the Al alloy waselectrically connected to a steel screen cathode forming a gal-vanic pair with a cathode/anode area ratio of50:1and immersed Fig.3Microstructure observed in samples aged at400ЊC(5h)with in a3%NaCl solution at ambient temperature for45days.A an additional heating of160ЊC(2h).Inset shows the development of 500cm3plastic container was filled with the NaCl solution a dendrite-like morphology in the eutecticand used as the anode test cell.Anode current capacity wasdetermined by weight loss.The total current that passed throughthe system was measured by a coulometer.Anode weight loss capacities are thus determined from knowledge of the total was determined at the end of the45day test when the samplescharge passed through the system and the weight loss of the were removed,cleaned,and weighed.Weight loss current anode sample.particles following the contours of the secondary dendritic arms.3.Results and DiscussionThe width of the space occupied by the black spherical particlesincreased from2m(in the as-cast ingot)toϳ6m(in thisA representative microstructure observed in the as-cast ingot,aging stage).Also,an additional feature was observed in regions as shown in Fig.1,consisted of␣-Al dendrites with sizesof the eutectic that correspond to the development of a dendrite-between130to150m.In the interdendritic regions,the pres-like pattern(inset in Fig.3).ence of eutectic and black spherical particles was observed.In order to qualitatively identify the species present in the The eutectic showed a white color with a maximum width ofas-cast ingot and in the aged specimens,x-ray diffractometry 10m,always following the contour of the dendritic arms.was applied;and,from the collected data,seven peaks were This eutectic,instead of presenting a platelet morphology asdetected in each condition.As expected,the main peaks corres-that reported in Ref5,showed the presence of rows formed byponded to the␣-Al phase.Also,the presence of binary precipi-gray spherical particles.tates of MgZn,Mg4Zn7,Mg7Zn3,MgZn2,AlMg,Al3Mg2, Figure2shows the microstructure observed in samples agedMg17Al12,Al4Li9,LiZn,and AlLi were detected;ternary at400ЊC(5h).The dendritic structure was modified,givingprecipitates of AlMg4Zn11,Al2MgLi,LiMgZn,and Al2Mg3Zn3 place to the coarsening of primary and secondary arms.Theand quaternary precipitates of Al0.9Li34.3Mg64.5Zn and white eutectic(with a maximum width of7m)started toAl0.9Li34.3Mg64.5Zn also appeared.The kind of precipitates and migrate toward future grain boundaries,leaving traces of thetheir respective d-spacings are shown in Table1.An interesting interdendritic species in the␣-Al matrix,which takes the mor-feature of these x-ray diffractograms was an increase in the phology of spherical particles.Also,it was observed that therelative intensity(I/I o)of peaks II,III,and VII for both aged spherical particles present as rows inside the white eutecticconditions,indicating,from a qualitative point of view,the started to growth(inset in Fig.2).The black spherical particlesprecipitation of particles containing Li.located at a secondary,dendritic arm spacing did not show anyIn addition,WDX microanalyses were carried out in speci-change at this stage.mens in both as-cast and as-aged conditions(Table2).For In order to evaluate the effect of a secondary aging treatment,example,in the as-cast specimens,it was possible to retain4.7 the samples aged at400ЊC for5h received an additional agingat.%Zn and4.2at.%Mg in␣-Al solid solution.The Li was treatment a160ЊC for2h more.The observed microstructurenot detected due to the characteristics of the detector.under this aging condition is shown in Fig.3,where thereappears to be an increase in the amount of black spherical In the first as-aged condition(400ЊC,5h),the amount of Table1Phases and compounds identified by x-ray diffractionAs cast Aged(a)Aged(b)Peak d(A˚)I/I o D(A˚)I/I o d(A˚)I/I o PhasesI 2.340100 2.334100 2.344100␣-Al,MgZn,Mg4Zn7,Mg7Zn3,AlMg,Al3Mg2,Al4Li9,AlMg4Zn11 II 2.02819 2.02353 2.02835␣-Al,AlMg4Zn11,Al2MgLiIII 1.43444 1.43249 1.43554␣-Al,MgZn,MgZn2,Mg17Al12,LiZn,LiMgZn,Al3Mg2IV 1.22438 1.22338 1.22414␣-Al,AlMg,AlLiV 1.1725 1.1714 1.1724Al0.9Li34.3Mg64.5ZnVI0.93260.932120.9325␣-Al,Al0.7Zn0.3,Al2Mg3Zn3VII0.90840.906190.90612AlLi,Al0.7Zn0.3,Al0.9Li34Mg64Zn,Al2Mg3Zn3(a)Aged at400ЊC,5h(b)Aged at400ЊC with an additional heating of160ЊC for2hTable2WDX microanalyses results of as-cast and aged specimens(in at.%)Condition(→)As cast Aged(a)Aged(b) Microstructure(↓)(at.%)(at.%)(at.%)␣-Al dendrites Al91.00Ϯ2.0……Mg 4.20Ϯ0.50 3.50Ϯ0.50 3.50Ϯ0.10Zn 4.70Ϯ0.20 3.22Ϯ0.65 4.00Ϯ0.15 White eutectic Al41.00Ϯ3.039.00Ϯ4.041.00Ϯ3.0 Mg32.00Ϯ1.033.00Ϯ2.032.00Ϯ2.5Zn27.00Ϯ3.028.00Ϯ1.527.00Ϯ3.6 Black particles Al………Mg71.00Ϯ2.072.00Ϯ2.5070.00Ϯ4.00Zn29.00Ϯ6.028.00Ϯ4.029.00Ϯ2.00(a)Aged at400ЊC,5h(b)Aged at400ЊC with an additional heating of160ЊC for2hFig.4(a)A photomicrograph of the specimen in the as-cast condition where the presence of a platelet-like precipitate is observed.(b)Selected area diffraction pattern of-Al2Zn3Mg3phase.(c)Spherical precipitates of Mg7Zn3.(d)Selected area diffraction pattern of the Mg7Zn3phase Zn and Mg present in the␣-Al solid solution decreased.This particles in the interdendritic region was observed,with an decay in both elements was attributed to the coarsening of thealmost constant composition.The only detected change in com-eutectic located in interdendritic regions.Regarding composi-position corresponded to the transition of the eutectic to a tion of this eutectic,the amount of Mg detected was in thedendritelike precipitate,whose composition corresponded to range of32to33at.%and the amount of Zn was in the range Al-16.6at.%Zn-13.25at.%Mg with a contamination of3.3 of27to28at.%,the remaining being Al.As mentioned before,at.%Fe.the black spherical particles observed in the interdendritic The TEM observations were performed in the specimens regions did not present any change,and their composition waswith and without heat treatment in order to identify the main almost constant,corresponding to precipitates of Mg7Zn3.In species present in the␣-Al matrix.Figure4(a)shows a photomi-the second aging stage,an increase in the amount of blackcrograph of the specimen in the as-cast condition,where theshowed an average value of67%,and the aged sample at400ЊC for5h with an additional heating of160ЊC for2h showedan average value of65%.It should be mentioned that recent research directed towardthe development of aluminum sacrificial anodes of the Al-Mg-Zn type reported[5]values of electrochemical efficiency between63and78%(Ϫ1082mV;SCE).These results were attributedto a good dispersion of thephase[7]in the␣-Al matrix,whichwas reached by a long-term aging treatment(400ЊC,24h),being the intermetallic compound responsible for the break-down of the passive film and at the same time leading to aquite generalized dissolution.When additions of In,Ga,andCa were made to the Al-Mg-Zn alloy,[8]and the resulting alloywas thermally treated at500ЊC(4h),the Al anodes reachedefficiencies up to95.6%(Ϫ1090mV;SCE).This excellentvalue of efficiency was attributed to a homogeneous distributionof Ga and a precipitation of In and Ca.Therefore,the researchhas shifted to the production of Al alloys,which can showhigh electrochemical efficiencies.To reach that goal,during thepresent research,the as-cast microstructure must be improved inorder to increase the electrochemical efficiency of Al anodesby means of decreasing or eliminating the presence of Mg7Zn3precipitates in interdendritic regions.The reason for moving tothis direction is that,during dissolution of the Al anode,theMg7Zn3particles did not dissolve.This provokes the isolationof some␣-Al dendrites,giving place to a localized pittingcorrosion mechanism and at the same time decreasing the elec-trochemical efficiency of the Al anode.On the other hand,itwas detected that precipitates of the-Al2Zn3Mg3and␦-AlLitype played an important role in terms of breaking down thealuminum oxide passive film,permitting at the same time acontinued galvanic activity and an increase of the electrochemi-cal efficiency of the Al anode.4.Conclusions•The resulting Al-Zn-Mg-Li alloy showed two kinds ofspecies in the interdendritic spacing,which correspondedto a eutectic of Al2Zn3Mg3and precipitates of Mg7Zn3. Fig.5(a)Morphology of precipitates rich in lithium.(b)Selectedarea diffraction pattern of the␦-AlLi precipitates•By means of TEM observations,the presence of the-Al2Mg3Zn3intermetallic compound,precipitates ofMg7Zn3,and␦-AlLi precipitation in the␣-Al matrix were presence of a platelet-like precipitate of about1800nm in lengthidentified,the presence of those species for the activation may be observed.Spherical precipitates(40to200nm),linkedof the aluminum electrode being relevant by means of by dislocations,are shown in Fig.4(c).Selected area diffractionpassive film breakdown,which can lead to a quite general-patterns taken in those precipitates identified them as the inter-ized dissolution of the Al anode.metallic-Al2Zn3Mg3(Fig.4b)and Mg7Zn3(Fig.4d).In bothaged conditions,besides detecting the presence of precipitates•In order to improve the electrochemical efficiency of theAl anode,it was apparent that research must be focused of the-Al2Zn3Mg3and the Mg7Zn3type,the presence of aprecipitate rich in lithium was also detected,as shown in Fig.toward the role played by the-Al2Zn3Mg3,Mg7Zn3,and␦-AlLi compounds in the␣-Al matrix,and toward the effect 5(a).This was identified by its selected area diffraction patternas␦-AlLi(Fig.5b),with an average size of80nm.of the decay of the eutectic and particles in interdendritic Regarding the electrochemical behavior in terms of effi-regions.This will result in the prevention of the formation ciency of the as-cast ingot and aged samples,it can be said of a continuous,adherent,and protective oxide film by that the efficiency of the as-cast ingot showed an average valueparticle precipitation,leading to a uniform dissolution of of62%,while the efficiency of aged samples at400ЊC(5h)the Al anode.Acknowledgments3.J.B.Clark:Trans.Am.Soc.Met.,1961,vol.53,p.295.4.G.M.Kuznetsov and A.D.Barsukov:Izv.Akad.Nauk,SSSR Met.,1986,The authors are grateful for the financial support by DGAPA,vol.4,p.198.Grant No.IN109398.The participation of Mr.E.Caballero and 5.A.Barbucci,G.Cerisola,G.Bruzzone,and A.Saccone:Electrochem. Eng.L.Ban˜os is also gratefully acknowledged.Acta,1997,vol.42,p.2369.6.R.J.Kilmer and G.E.Stonere:Light Weight Alloys for Aerospace Appli-cations II,TMS,Warrendale,PA,1991,p.3.References7.D.A.Petrov:in Ternary Alloys,G.Petzow and G.E.Effemberg,eds.,1993,vol.7,p.57.1.A.R.Despic:J.Appl.Electrochem.,1976,vol.6,p.499.2.M.Salleh:Ph.D.Thesis,UMIST,Manchester,United Kingdom,1978.8.X.Zhand and Y.Wang:Corr.Sci.Protection,1995,vol.7(1),p.53.。