武汉理工材料概论重点

Definition 材料的定义：The materials making up the surrounding world consist of discrete partic les, having a subm icr oscopic size.Atomic structure and the nature of bonds(原子结构和化学键)—metals and their alloys (metallic bonding 金属键) —organic polymer s 有机聚合物(c ovalent bonding and sec ondary bonding 共价键和二次键)—c er am ic s (ionic bonding and covalent bonding) Mechanical properties：力学性能Which r eflect the behavior of materials, defor med by a set of forc es （概念）Four basic types of stresses : tensile, c ompr essive, shear ,tor sion (拉力，压力，剪切力，扭转力) Physical properties:物理性能the behavior of materials subj ected to the action of temper ature, electric or magnetic fields, or light.电性能Electric properties磁性能Magnetic pr operties热性能Ther mal pr operties光性能Optic al pr opertiesChemical properties:化学性能Which char acterize the behavior of material in a reactive environment. （概念）The four basic aspects of materials scienc e and tec hnology ar e: manufacturing processing, structure,properties and performances结构－性能－工艺之间的关系：First, the processing of a materi al aff ects the structure, second the original structure and properties determine how we can process the material to produce a desired shape一、METAL:（金属）1、金属最显著的特性：good conductors of heat and electricity (热导性，电导性)2、性能:are opaque to visible light; are hard, rigid; can undergo plastic deformation; have a high melting temperature3、金属的晶体点阵：crystal structur e（晶体结构）: body-center ed c ubic structur e , fac e-center ed cubic structure , hexagonal close-pac ked structur e（体型、面型，六角形放射状）4、properties of alloys（合金的性能）:(more carbon ,more brittle.) have relatively high thermal and electrical conductivities; good energy absorption characteristics ;nonmagnetic properties 5、铸铁概念：c ast iron, essentially an alloy of ir on, carbon and silic on, is c omposed of ir on and fr om2 to 6.67 percent c ar bon, plus manganese, sulfur, and phosphorus, and shaped by being c ast in a mold. 6、The types and properties of cast iron ；white cast iron( hard , brittle ) , gray cast iron (brittle ,withstand large compressive loads but small tensile loads ), alloy cast iron , nodular or ductile cast iron (good castability ,toughness, good wear resistance ,low melting point ,and hardenability ), malleable cast iron (strength ,toughness, ductility ,and machinability)7、carbon steels（碳钢）：low carbon steels（含碳0.05~0.32%）；medium c ar bon steels（含碳0.35~0.55%）；high c ar bon steels（含碳0.60~1.50%）8、不锈钢：ther e are thr ee types of stainless steels: --the martensitic types；the ferritic types ；the austenitic types9、advantages of using Al: one-third of the weight of steel ;good thermal and electrical conductivity ;high strength-to-weight ratio ;can be given a hard surf ace by anodizing and hard coating ;most alloys are weldable ;will not rust ;high ref lectivity ;can be die cast ;easily machined ;good f ormability; nonmagnetic ;nontoxic and one–third of the stif f ness of steel.10、c opper is known for its high ther mal (热导性)and electric al conductivity.11、crystal structure : body-centered cubic structure (barium), face-centered cubic structure (copper),hexagonal close-packed structure (z inc)二、CERA MIC（陶瓷）1、The property of ceramics （陶瓷的性质）Extreme hardness（硬度高） Heat r esistanc e Corrosion r esistanc e Low electrical and ther mal conductivity Low ductility (brittleness)2、Porosity（孔隙度）Open porosity: refer s to the network of por es in a material that is open to the surfac e and into whic h a liquid such as water can penetr ate if the part were submer ged in it。

Closed porosity: refers to those pores that have bec ome sealed within the gr ain structur e 。

Pores affect the strength of ceramics in two ways：（影响强度的毛孔陶瓷两种方式）①、they produc e stress c onc entr ations. Once the str ess r eaches a critic al level, a crac k will for m andpropagate.②、por es r educ e the cross-sectional areas over whicha load c an be applied and,c onsequently, lower the str ess that these materials c an support。

Conventional ceramic processing（传统陶瓷处理）；manuf acture of the powder ,its calcinations ,milling ,grading and mixing ,incorporating additives ,shape f orming , drying and densif i cation.三、GLASS（玻璃）1、the measur ed mec hanic al strength of glass is much lower than the theor etical str engthcauses of this loss of str ength ：①、the pr esenc e of surfac e defects, suc h as c aused by c hem ic al c orrosion or mec hanic al abr asion。

②、If the glass is cooled too r apidly it does not have time to r elease str esses set up within it during cooling . these ar e "frozen-in" and c an c ause the glass to shatter when it becomes a solid.the transparency is explained by two properties : first ,it has no surface of internal structure which gives reflection or scattering。