专业课课件中文版5第五章

应该说，我们对晶体缺陷的认识还不全面。随着理论深化、表征的完1234Alloy:合Ametallicsubstancethatiscomposedoftwoormore(Concentrationspecificationonthebasisofweight(ormass)ofaparticularelementrelativetothetotalalloyweight(ormass).Stoichiometry:正常价化合Forioniccompounds,thestateofhavingexactlytheratioofcationstoanionsspeci-fiedbythechemicalformula.在离子化合物中，正、负离子的比例严格遵守化学定义的化合价关系Imperfection:缺陷，不完整Adeviationfromperfection;normallyappliedtocrystallinematerialswhereinthereisadeviationfromatomic/molecularorderand/orcontinuity.对完美性的偏离，在材料科学领域中通常指晶体材料中原子/分子在排列顺序/Pointdefect:点缺Acrystallinedefectassociatedwithoneor,atmost,severalatomicVacancy:空AnormallyoccupiedlatticesitefromwhichanatomorionisVacancydiffusion:空位Thediffusionmechanismwhereinnetatomicmigrationisfromlatticesitetoanadjacentvacancy.Self-interstitial:自间隙原AhostatomorionthatispositionedonaninterstitiallatticeSchottkydefect:肖脱基缺Inanionicsolid,adefectconsistingofacation–vacancyandanion–vacancyAtomicvibration:原子ThevibrationofanatomaboutitsnormalpositioninaSubstitutionalsolidsolution:置换固溶AsolidsolutionwhereinthesoluteatomsreceorsubstituteforthehostInterstitialdiffusion:间隙Interstitialsolidsolution:间隙固溶Asolidsolutionwhereinrelativelysmallsoluteatomsoccupyinterstitialpositionsbetweenthesolventorhostatoms.Solidsolution:Ahomogeneouscrystallinephasethatcontainstwoormorechemicalspecies.Bothsubstitutionalandinterstitialsolidsolutionsarepossible.Solid-solutionstrengthening:固溶体强Hardeningandstrengtheningofmetalsthatresultfromalloyinginwhichasolidsolutionisformed.ThepresenceofimpurityatomsrestrictsdislocationSolute:溶Onecomponentorelementofasolutionpresentinaminorconcentration.Itisdissolvedinthesolvent.溶液（固溶体）中，含量较少的组元或元素。溶质溶解在溶剂Solutionheattreatment:固溶处理，均匀化退TheprocessusedtoformasolidsolutionbydissolvingprecipitateOften,thesolidsolutionissupersaturatedandmetastableatambientconditionsasaresultofrapidcoolingfromanelevatedtemperature.Solvent:溶Thecomponentofasolutionpresentinthegreatestamount.Itisthecomponentthatdissolvesasolute.溶液（固溶体）中，含量最大的组元，此组元溶解了溶质Burgersvectorb):柏氏矢AvectorthatdenotesthemagnitudeanddirectionoflatticedistortionassociatedwithaCompositionCi):成分，组Therelativecontentofaparticularelementorconstituent(i)withinanalloy,usuallyexpressedinweightpercentoratompercent.Defectstructure:缺陷结构，缺陷组RelatingtothekindsandconcentrationsofvacanciesandinterstitialsinaceramicDislocation:位Alinearcrystallinedefectaroundwhichthereisatomicsticdeformationcorrespondstothemotionofdislocationsinresponsetoanshearstress.Edge,screw,andmixeddislocationsareScrewdislocation:螺型位Alinearcrystallinedefectassociatedwiththelatticedistortioncreatedwhennormallyparallelnesarejoinedtogethertoformahelicalramp.TheBurgersvectorisparalleltothedislocationMixeddislocation:混合AdislocationthathasbothedgeandscrewDislocationdensity:位错Thetotaldislocationlengthperunitvolumeofmaterial;alternay,thenumberofdislocationsthatintersectaunitareaofarandomsurfacesection.Dislocationline:位错Thelinethatextendsalongtheendoftheextrahalf-neofatomsforanedgedislocation,andalongthecenterofthespiralofascrewdislocation.Edgedislocation:刃型位Alinearcrystallinedefectassociatedwiththelatticedistortionproducedinthevicinityoftheendofanextrahalfneofatomswithinacrystal.TheBurgersvectorisperpendiculartothedislocationElectroneutrality:电中Thestateofhavingexactlythesamenumbersofpositiveandnegativeelectricalcharges(ionicandelectronic),thatis,ofbeingelectricallyneutral.Frenkeldefect:弗仑克尔缺Inanionicsolid,acation–vacancyandcation–interstitialGrain:晶AnindividualcrystalinapolycrystallinemetalorGrainboundary:晶TheinterfaceseparatingtwoadjoininggrainshavingdifferentcrystallographicGraingrowth:晶粒Theincreaseinaveragegrainsizeofapolycrystallinematerial;formostmaterials,anelevated-temperatureheattreatmentisnecessary.Grainsize:晶粒尺TheaveragegraindiameterasdeterminedfromarandomcrossMicroscopy:显微术，显微镜TheinvestigationofmicrostructuralelementsusingsometypeofMicrostructure:显微组Thestructuralfeaturesofanalloy(e.g.,grainandphasestructure)thataresubjecttoobservationunderamicroscope.在显微镜下观察到的某合金的结构特征（例如：晶粒和相的组织结构特征Photomicrograph:显微组织Thephotographmadewithamicroscope,whichrecordsamicrostructural在显微镜下拍摄，记录显微组织结构形态的Scanningelectronmicroscope:扫描电子显微镜Amicroscopethatproducesanimagebyusinganelectronbeamthatscansthesurfaceofaspecimen;animageisproducedbyreflectedelectronbeams.Examinationofsurfaceand/ormicrostructuralfeaturesathighmagnificationsis使用一束电子流扫描样品表面用样品产生的反射产生图象的一种显微镜Scanningprobemicroscope:扫描探针显微镜Amicroscopethatdoesnotproduceanimageusinglightradiation.Rather,averysmallandsharpproberasterscansacrossthespecimensurface;out-of- deflectionsinresponsetoelectronicorotherinctionswiththeprobearemonitored,fromwhichatopographicalmapofthespecimensurface(onananometerscale)is一种不用光学射线产生图象，而是用非常的探针依次横扫描过样品表面Transmissionelectronmicroscope:透射电子显微Amicroscopethatproducesanimagebyusingelectronbeamsthataretransmitted(passthrough)thespecimen.ExaminationofinternalfeaturesathighmagnificationsisExampleProblem5.1(晶体中点缺陷的平衡浓度分析Calculatetheequilibriumnumberofvacanciespercubicmeterforcopperat1000℃.Theenergyforvacancyformationis0.9eV/atom;theatomicweightanddensity(at1000°C)forcopperare63.5g/moland8.40g/cm3,respectively.NNexp(Qv kTNAexp(Qv kT(6.0231023atoms/mol)(8.40g/cm3)(106cm3/m3)

63.5g/

exp(8.62105eV/K)(1273K) 2.21025vacancies/FartherNvexp(QN exp(Q

(8.62105eV/K)(1273K)2.74由此可见材料中缺陷数是一个非常大的绝对量，但是一个非常小的比例5.28CopperandtinumbothhavetheFCCcrystalstructureandCuformsasubstitutionalsolidsolutionforconcentrationsuptoapproximay6wt%Cuatroomtemperature.Computetheunitcelledgelengthfora95wt%Pt-5wt%Cualloy.5.29CitetherelativeBurgersvector–dislocationlineorientationsforedge,screw,andmixeddislocations.5.31(a)Thesurfaceenergyofasinglecrystaldependsonthecrystallographicorientationwithrespecttothesurface.Exinwhythisisso.(b)ForanFCCcrystal,suchasaluminum,wouldyouexpectthesurfaceenergyfor(100)netobegreaterorlessthanthatfora(111)ne?Design5.D1*Aluminum-lithiumalloyshavebeendevelopedbytheaircraftindustryinordertoreducetheweightandimprovetheperformanceofitsaircraft.Acommercialaircraftskinmaterialhavingadensityof2.55g/cm3isdesired.ComputetheconcentrationofLi(inwt%)thatisrequired.5.D2*IronandvanadiumbothhavetheBCCcrystalstructureandVformsasubstitutionalsolidsolutioninFeforconcentrationsuptoapproximay20wt%Vatroomtemperature.DeterminetheconcentrationinweightpercentofVthatmustbeaddedtoirontoyieldaunitcelledgelengthof0.289nm.五、背景资晶体缺陷的研究于矿物学的研究。矿物学家从有的石英晶体中发现它18世纪末冶金学家注意到从白炽状态缓冷下来的熟铁晶粒中有亚结构存在。19世纪下半叶冶金学家研究晶粒间界，猜测其厚度为原子尺度。20世纪初期物理学家研究金属的范性，首先在钠单晶上发现滑移带，W.H.布喇格猜测1912M.von劳厄用X射线入射晶体而产生衍射斑，方始证实晶体内1914年，C.G.达尔文从X射线衍射动力学理论出发计算，得出完整晶体的