机械工程材料双语课件2)

2.2Crystalstructuresofmetals2.2.1CrystalstructuresofpuremetalsMetalatomsarecombinedbytheinteractionbetweenthepositiveionsandthefreeelectrons,namedmetallicbonds.Metalstendtoarraytightly.价电子云正离子MetallicbondsMetalshavegoodthermalconductivity,electricconductivity,ductilityandmetallicbrightness.Thecommoncrystallatticetypeofpuremetalsarebodycenteredcubic(bcc),facecenteredcubic(fcc),andclose-packedhexagonal.二、金属的晶体结构•1、纯金属的晶体结构•金属原子是通过正离子与自由电子的相互作用而结合的，称为金属键。•金属原子趋向于紧密排列。价电子云正离子金属键示意图具有良好的导热性、导电性、延展性及金属光泽。常见纯金属的晶格类型有体心立方(bcc)、面心立方(fcc)和密排六方(hcp)晶格。⑴BodycenteredcubiccrystallatticeBodycenteredcubiccrystallatticeParametersforbodycenteredcubiccrystallatticeBodycenteredcubiccrystallatticeAtomicity:2Coordinationnumber:8Tightness:0.68Frequentmetals:-Fe,Cr,W,Mo,V,Nb,etc.Crystallatticeconstants:a(a=b=c)ar43Atomradius:•体心立方晶格原子个数：2配位数：8致密度：0.68常见金属：-Fe、Cr、W、Mo、V、Nb等晶格常数：a(a=b=c)ar43原子半径：⑵FacecenteredcubiccrystallatticeFacedcenteredcubiccrystallatticeParametersforfacecenteredcubiccrystallatticea42r：Atomradius:Atomicity:4Coordinatenumber:12Tightness:0.74Frequentmetals:-Fe,Ni,Al,Cu,Pb,Au,etc.Crystallatticeconstant:aFacecenteredcubiccrystallatticea42r：原子半径原子个数：4配位数：12致密度：0.74常见金属：-Fe、Ni、Al、Cu、Pb、Au等晶格常数：a•面心立方晶格⑶Closed-packedhexagonalcrystallatticeParametersforclosed-packedhexagonalcrystallatticea21r：Atomradius:Atomicity:6Coordinatenumber:12Tightness:0.74Frequentmetals:Mg,Zn,Be,Cd,etc.Crystallatticeconstant:sidelengthofbasefaceaandc,c/a=1.633Closed-packedhexagonalcrystallatticea21r：原子半径原子个数：6配位数：12致密度：0.74常见金属：Mg、Zn、Be、Cd等晶格常数：底面边长a和高c，c/a=1.633•密排六方晶格⑷closed-packedplanesandorientationsofthethreeordinarycrystallatticesAtomicityonunitareaofthecrystalplaneiscalledcrystalplaneatomicdensity.Atomicityonunitlengthofthecrystalorientationiscalledcrystalorientationatomicdensity.Thecrystalplaneorcrystalorientationwiththelargestatomicdensityiscalledclosedpackedplaneorclosedpackedorientation.Closed-packedplanesamountClosed-packedorientationsamountBodycenteredcubiccrystallattice{110}61114Facecenteredcubiccrystallattice{111}41106Closed-packedhexagonalcrystallatticeBottomofthehexagonal1Diagonallineofthebottom3•⑷三种常见晶格的密排面和密排方向•单位面积晶面上的原子数称晶面原子密度。•单位长度晶向上的原子数称晶向原子密度。•原子密度最大的晶面或晶向称密排面或密排方向。密排面数量密排方向数量体心立方晶格{110}61114面心立方晶格{111}41106密排六方晶格六方底面1底面对角线3•closed-packedplanesandorientationsofthethreeordinarycrystallattices六方底面底面对角线密排六方晶格面心立方晶格体心立方晶格•三种常见晶格的密排面和密排方向六方底面底面对角线密排六方晶格面心立方晶格体心立方晶格体心立方(110)面面心立方(111)面密排六方底面Stacksequenceoftheclosed-packedplaneinfacecenteredcubiccrystallatticeandclosed-packedhexagonalcrystallatticeStacksequenceofclosed-packedhexagonalcrystallatticeisABABAB…StacksequenceoffacecenteredcubiccrystallatticeisABCABCABC…•面心立方晶格与密排六方晶格密排面的堆垛顺序•密排六方晶格的堆垛顺序为ABABAB…•面心立方晶格的堆垛顺序为ABCABCABC…•Atomstackoffacecenteredcubiccrystallattice•面心立方晶格的原子堆垛