材料科学概论复习题有点接近完整版

一、名词解释ReactionbondingAceramicprocessingtechnique,bywhichashapeismadeusingonematerialthatislaterconvertedintoaceramicmaterialbychemicalreactionandsintering.反应烧结：一种陶瓷加工技术,是用一种材料经过化学反应和烧结而转变成陶瓷材料的成型方法。Materialsscienceandengineeringisaninterdisciplinaryfieldconcernedwithinventingnewmaterialsandimprovingpreviouslyknownmaterialsbydevelopingadeeperunderstandingofthemicrostructure-composition-synthesis-processingrelationships.材料科学与工程：是一个关于开明新材料和通过对“微观结构——组成——合成——加工”关系加深理解而提高已有材料的跨学科领域Structuremeansadescriptionofthearrangementsofatomsorionsinamaterial结构：是对材料中原子或离子排列方式的描述Compositionmeansthechemicalmake-upofamaterial.组成：表示材料的化学组成Trans-granular(晶内的，穿晶的)Fracturefractureinwhichcrackswouldgothroughthegrains.穿晶断裂：沿着纹理断裂的断裂DuctileFractureInmetalsthathavegoodductilityandtoughness,ductilefracturenormallyoccursinatrans-granularmethod.Often,aconsiderableamountofdeformation-includingneckingisobservedinthefailedcomponent韧性断裂：金属有很好的延性和韧性，韧性断裂常常发生在穿晶断裂中。通常，可以在失效部件中看到可观的包括变细在内的变形。GlassIntermediatesOxidesthat,whenaddedtoaglass,helptoextendtheglassynetwork;althoughtheoxidesnormallydonotformaglassthemselves.网络中间体：加入玻璃中，有助于延伸玻璃网状结构的氧化物，但他们通常不能独自形成玻璃。shotpeeningAprocessinwhichmetalspheresareshotatacomponent.Thisleadstoaresidualcompressivestressatthesurfaceofacomponentandthisenhancesfatiguelife.喷丸硬化：把金属球喷入部件中的过程，导致部件表面产生残余压缩应力，这提高疲劳寿命。FlexuralmodulusThemodulusofelasticitycalculatedfromtheresultsofabendtest,givingtheslopeofthestress-deflection(偏转)curve弯曲模量：是从弯曲试验结果中计算出来的弹性模量，等于应力——偏转曲线的斜率。TemperingAlow–temperatureheattreatmentusedtoreducethehardnessofmartensite(马氏体)bypermittingthemartensitetobegintodecomposetotheequilibriumphase.回火：一种通过让马氏体分解成平衡相而减小马氏体硬度的低温热处理方法StressForceorloadperunitareaofcross-section(横界面)overwhichtheforceorloadisacting应力：在力或负荷作用下单位横截面积的力或负荷StrainElongation(延长)changeindimensionperunitlength.应变：在单位尺寸长度中改变的伸长度Young’smodulusTheslope(斜率)ofthelinear(线性的)partofthestress-straincurveintheelastic(弹性的)region(区域的),sameasmodulusofelasticity(弹性系数).杨氏模量：在应力—应变曲线的弹性区域中线性部分的斜率，和弹性模量相同。Synthesisistheprocessbywhichmaterialsaremadefromnaturallyoccurringorotherchemicalreaction合成：通过自然生成或其他化学反应而制成材料的过程Processingmeansdifferentwaysforshapingmaterialsintousefulcomponentsorchangingtheirproperties.加工：用不同的方法把材料成型成有用的部件或者改变他们的性能。AspectratioThelengthofafiberdividedbyitsdiameter.纵横比：纤维的长度除以它的直径DelaminationSeparationofindividualpliesofafiber-reinforcedcomposite.分层：在纤维增强复合材料中独特板层的分隔Ductiletobrittletransitiontemperature(DBTT)Thetemperaturebelowwhichamaterialbehavesinabrittlemannerinanimpacttest韧脆转变温度：在此温度下材料在冲击试验中表现脆性CreeprateTherateatwhichamaterialdeformswhenastressisappliedatahightemperature蠕变速率：材料在高温时应力作用下的变形速率。RupturetimeThetimerequiredforaspecimentofailbycreepataparticulartemperatureandstress断裂时间：在一定温度和应力下，样本因蠕变而失效所需的时间FatiguelifeThenumberofcyclespermittedataparticularstressbeforeamaterialfailsbyfatigue疲劳寿命：在一定应力下，材料在疲劳失效前所允许的循环使用次数EndurancelimitAnolderconceptthatdefinedastressbelowwhichamaterialwillnotfailinafatiguetest.疲劳极限：这是一个很老的概念，定义为一个应力，它低于材料在疲劳测试中永不会失效的临界应力TapecastingAprocessformakingthinsheetsofceramicsusingaceramicslurryconsistingofbinders(粘结剂),plasticizers(可塑剂),etc.Theslurryiscastwiththehelpofablade(刀片)ontoaplasticsubstrate.流延成型：用粘结剂和可塑剂等组成的陶瓷浆料制造陶瓷薄片的过程，陶瓷浆料在刀片帮助下浇铸到塑料基板上。TruestressTheloaddividedbytheactualcross-sectionalareaofthespecimenatthatload.真实应力：样本的负荷除以在该负荷下的实际横截面积FatiguestrengthThestressrequiredtocausefailurebyfatigueinagivennumberofcycles疲劳强度：在给定循环次数下导致材料疲劳失效所需的应力NotchsensitivityMeasurestheeffectofanotch,scratch(剐擦敏感度)-,orotherimperfection（不完整性,非理想性）onamaterial’sproperties,suchastoughnessorfatiguelife缺口灵敏度：衡量缺口、擦痕或其他不完整结构对材料性能的影响，比如对韧性和疲劳寿命的影响LinearpolymerAnypolymerinwhichmoleculesareintheformofspaghetti-likechains(类似与意大利细面条).线状聚合物：分子以类似意大利细面条的链的形式存在的所有聚合物Brittlestress-rupturefailuresusuallyshowlittleneckingandoccurmoreoftenatsmallercreepratesandhightemperatures.脆性应力断裂失效：常常展现比较小的颈缩，通常在很小的蠕变速率和高温下发生Creepatimedependent,permanentdeformationathightemperature,occurringatconstantloadorconstantstress蠕变：在高温下，加载恒定载荷或者恒定应力时发生的随时间变化的永久变形Stress-corrosionAphenomenoninwhichmaterialsreactwithcorrosivechemicalsintheenvironmentleadingtotheformationofcracksandloweringofstrength应力腐蚀：材料和环境中有腐蚀性的化学物质反应而导致裂纹形成和强度降低的一种现象RuleofmixturesThestatementthatthepropertiesofacompositematerialareafunctionofthevolumefractionofeachmaterialinthecomposite混合定律：表示复合材料的性能与复合材料中每种材料所占比例有关TrueporosityThepercentageofaceramicbodythatiscomposedofbothclosedandinterconnectedporosity真实孔隙率：陶瓷基体中闭口孔和连通孔所占的百分比ElectricalContactsMaterials,usedforelectricalcontactsinswitches（交换机）andrelays(继电器)musthaveagoodcombinationofwearresistanceandelectricalconductivity.电触头：在交换机和继电器中的电触头所使用的材料必须使耐磨性和导电性很好相结合Polymersthesematerialsaremadeupofmany(poly)identicalchemicalunits(mers)thatarejoinedtogethertoconstructgiantmolecules(巨大的分子).聚合物：这些材料由很多连结在一起的相同化学单元组成，构成巨大的分子Tensiletoughnesstheenergyabsorbedbyamaterialpriortofracturing(断裂)断裂韧性：在断裂前材料能吸收的能量Ductilitytheamountofdeformationthatamaterialcanwithstandwithoutbreaking延展性：一个材料所能承受的且不会断裂的变形大小Truestrain\Thestraincalculatedusingactual（notoriginal）dimensions,givenbyet=ln(l/l0)=ln(A/A0)真实应变：用实际尺寸计算的应变，也就是et=ln(l/l0)=ln(A/A0)Glass-ceramicsarecrystallinematerialsthatarederivedfromamorphousglasses.Usually,glass-ceramicshaveasubstantiallevelofcrystallinity(~>70-99%).微晶玻璃：起源于无定型玻璃的晶体材料，通常，微晶玻璃有很高的结晶度(~>70-99%)AdditionPolymerizationProcessbywhichpolymerchainsarebuiltupbyaddingmonomers(单体)togetherwithoutcreatingabyproduct(副产品).加聚反应：通过加上单体而形成聚合物链且不产生副产品的一个过程CondensationPolymerizationApolymerizationmechanisminwhichasmallmolecule(e.g.,water,methanol,etc.)iscondensedoutasabyproduct缩聚反应：有小分子（比如水、甲醇等）作为副产品从反应中凝结出来的聚合机理DeflectiontemperatureThetampertureatwhichapolymerwilldeformagivenamountunderastandardload.变形温度：在给定大小的标准负荷下使聚合物变形的温度DegreeofPolymerizationTheaveragemolecularweightofthepolymerdividedbythemolecularweightofthemonomer.聚合度：聚合物平均分子量除以聚合单元分子量InjectionmoldingAprocessingtechniqueinwhichathermoplasticmass(loadedwithceramicpowder)ismixedinanextruder-likesetupandtheninjectedintoadietoformcomplexparts.Inthecaseofceramics,thethermoplasticisburntoff.注射成型：Conchoidalfracture(贝壳状的断裂)Fracturesurfacecontainingaverysmoothmirrorzoneneartheoriginofthefracture,withtearlinescomprisingtheremainderofthesurface.贝壳状断裂:;裂纹表面包含一个在断裂起源处非常平滑的镜带，剩下的表面由撕裂线组成。Poisson’sratiolongitudinalelasticdeformation(纵向变形)tothelateraldeformation（横向变形）occurringatthesametimebyatensileorcompressivestress.泊松比：在相同时间下由拉应力或压应力产生的纵向弹性变形和横向变形之比BulkdensityThemassofaceramicbodyperunitvolume,includingclosedandinterconnectedporosity体积密度：单位体积（包括闭口空和连通孔）陶瓷体的质量PowdermetallurgyPowderprocessingroutesusedforconvertingmetalandalloypowdersintousefulshapes粉末冶金：把金属和合金粉末变成有用形状的粉体加工方法。Temperedglassisproducedbyquenching(淬火)thesurfaceofplateglasswithaircausingthesurfacelayerstocoolandcontract.Whenthecentercools,itscontractionisrestrainedbythealreadyrigidsurface,whichisplacedincompression淬火玻璃：平板玻璃表面在空气中淬火导致表面层冷却并契合，当中心冷却时，紧缩被刚性表面限制，表现出压应力GlasstemperatureAtemperaturebelowwhichanotherwiseductile(延展性)materialbehavesasifitisbrittle玻璃化温度：在此温度下拥有延展性的金属表现出脆性GlassformersOxideswithahigh-bondstrengththateasilyproduceaglassduringprocessing玻璃形成体：在加工过程中很容易形成玻璃的一种高键能氧化物。IntermediatesOxidesthat,whenaddedtoaglass,helptoextendtheglassynetwork;althoughtheoxidesnormallydonotformaglassthemselves.中间体：是一种氧化物，加入玻璃中时有助于延伸玻璃网状结构，尽管这种氧化物不能独自形成玻璃。stiffnessAqualitativemeasureoftheelasticdeformationproducedinamaterial.刚度：在金属中产生的弹性变形的定性表述FracturemechanicsThestudyofamaterial’sabilitytowithstandstressinthepresenceofaflaw断裂力学：在存在裂纹时材料所能承受的应力的研究Synthesisistheprocessbywhichmaterialsaremadefromnaturallyoccurringorotherchemicals合成：通过自然生成或其他化学反应而制成材料的过程ApparentporosityThepercentageofaceramicbodythatiscomposedofinterconnectedporosity虚表孔率：连通的的孔隙度占陶瓷体的百分比。TrueporosityThepercentageofaceramicbodythatiscomposedofbothclosedandinterconnectedporosity真实气孔率：由闭合的和连通的的孔隙度所组成的占陶瓷体的百分比。VulcanizationCross-linkingelastomerchainsbyintroducingsulfurorotherchemicals.橡胶的硫化：通过引入硫或其它化学物质使弹性体链交联。DegradationtemperatureThetemperatureabovewhichapolymerburns,chars,ordecomposes降解温度：高于聚合物燃烧,烧焦,或分解的温度ThermoplasticelastomersThesearepolymers(thermoplasticsorlightlycross-linkedthermosets)thathaveanelastic(弹性形变)deformation>200%.热塑性弹性体这些都是具有弹性形变>200%聚合物(热塑性塑料或轻度交联热固性材料)。UnsaturatedbondThedouble-oreventriple-covalentbondjoiningtwoatomstogetherinanorganicmolecule.不饱和键：在一个有机分子中两个原子之间的双键或是三键。FunctionalityThenumberofsitesonamonomeratwhichpolymerization(聚合作用)canoccurBranchedpolymerInabranchedpolymer,thereareprimarypolymerchainsandsecondaryoffshoots(分支)ofsmallerchainsthatstemfromthesemainchains.支链型高分子Crystallinityreferstothedegreeofstructuralorderinasolid结晶度：是指在固体中结构秩序的程度。TacticityDescribesthelocationinthepolymerchainofatomsoratomgroupsinnon-symmetricalmonomers(非对称性单体).立构规整度NeckingLocalizeddeformation(局部变形)ofaductilematerialduringatensiletestproducesaneckedregion(收缩区).颈缩：拉伸试验时塑性材料局部变形产生一个收缩区。Elasticlimitthecriticalstress(临界应力)valueneededtoinitiateplasticdeformation(开始塑性变形)ordislocationmotion(位错运动).弹性极限：开始塑性变形或位错运动临界应力值。TensilestrengththestressatwhichNeckingbeginsinductilematerials.抗张强度：塑性材料开始颈缩时的压力。Stress-corrosionAphenomenoninwhichmaterialsreactwithcorrosivechemicalsintheenvironmentleadingtotheformationofcracksandloweringofstrength应力腐蚀：材料对于环境中的腐蚀性化学物质反应导致裂缝的形成和强度的降低的现象。ChevronpatternAcommonfracturefeatureproducedbyseparatecrackfrontspropagatingatdifferentlevelsinthematerial回纹状图案：由材料的不同层次上单独的裂纹扩散引起的常见断裂特征ClimbMovementofadislocationperpendicular(垂直的)toitsslipplanebythediffusionofatomstoorfromthedislocationline攀移：位错线的运动垂直于原子运动的滑动面或位错。ImpactenergyTheenergyrequiredtofractureastandardspecimenwhentheloadisappliedsuddenly冲击能量：标准试样突然施加外加载荷时断裂所需的能量。ImpacttoughnessEnergyabsorbedbyamaterial,usuallynotched(有凹槽的),duringfracture,undertheconditionsofimpacttest冲击韧性：在冲击试验的条件下，通常切口(有凹槽的)的材料断裂过程中所吸收的能量。,ParticulatecompositesRuleofmixturesThestatementthatthepropertiesofacompositematerialareafunctionofthevolumefractionofeachmaterialinthecomposite混合物的颗粒混合法则：复合材料中每个材料的体积分数的函数的复合材料的性质RelaxationtimeApropertyofapolymerthatisrelatedtotherateatwhichstressrelaxationoccurs.松弛时间：与发生应力松弛速率相关的聚合物的性能。CrackGrowthRatetherateofpropagationofacrack裂纹扩展速率：裂纹扩展的速度Copolymer共聚物MacrohardnessOverallbulkhardnessofmaterialsmeasuredusingloads>2N.宏观硬度：使用加载>2N测得的材料的整体硬度。MicrohardnessHardnessofmaterialstypicallymeasuredusingloadslessthan2NusingsuchtestasKnoop(HK努普硬度).微观硬度：通常使用努普测试方法使用负载小于2N测得的材料硬度。Nano-hardnessHardnessofmaterialsmeasuredat1-10nmlengthscaleusingextremelysmall(~100µN)forces纳米硬度：在1-10纳米尺度使用非常小（〜100μN）力所测的材料的硬度Shearmodulus(G，剪切模量)-Theslopeofthelinearpartoftheshearstress-shearstraincurve剪切模量：剪切应力剪切应变的线性部分的斜率。ViscosityMeasureofresistancetoflow,definedastheratioofshearstresstoshearstrainrate(unitsPoiseorPa·s).粘度：流动阻力的衡量指标,定义为剪切应力与剪切应变率的比率(单位是~)。Strainratetherateatwhichstraindevelops应变速率：应变变化的速率Load.Theforceappliedtoamaterialduringtesting.载荷：在测试期间施加于材料的力。ThermoplasticsLinearorbranchedpolymersinwhichchainsofmoleculesarenotinterconnectedtooneanother.热塑性塑料EngineeringstressTheappliedload,orforce,dividedbytheoriginal(原始的)cross-sectional(交叉的)areaofthematerial.工程应力：外加负载,或力,除以材料的原始(原始的)横截面(交叉的)区域。EngineeringstrainTheamountthatamaterialdeformsperunitlengthinatensiletest工程应变：材料在拉伸试验单位长度的变形量。GeometricisomerAmoleculethathasthesamecompositionas,butastructuredifferentfrom,asecondmolecule.同分异构体：拥有相同的成分,但结构不同于第二个分子的分子。Cross-linking交联Attachingchainsofpolymerstogethertoproduceathree-dimensionalnetworkpolymer.TheRuleofMixturesinFiber-ReinforcedCompositesAsforparticulatecomposites,theruleofmixturesalwayspredictsthedensityoffiber-reinforcedcomposites:wherethesubscriptsmandfrefertothematrixandthefiber.Notethatfm=1-ff.纤维增强复合材料的混合法则对于颗粒复合材料,混合定理总是预测纤维增强复合材料的密度:下标m和f代表基底和纤维。注意,fm=1-ff。二、英译汉1.Ceramicmaterialsaregenerallycomposedofatleasttwoelements:one(ormore)ametallicelementandonenon-metallic.Metaloxides(Al2O3,ZrO2,FeO,etc.)arecommonexamplesofceramics,butothercompoundssuchascarbidesandnitridesarealsoincluded.Themostcommonelementsintheearth‘scrustaresiliconandoxygen,andsilica(SiO2)isthemostcommoncomponentofceramicsandglasseseventhoughformostpurposeswewouldnotconsiderSiametallicelement.Thetypeofchemicalbonds:covalentbond,ionicbondandvanderwaalsbond.陶瓷材料一般是由至少两个元素:一个(或多个)金属元素和非金属。金属氧化物(氧化铝、氧化锆、FeO说等等)是常见的陶瓷的例子,但其他化合物碳化物和氮化物等也包括在内。硅和氧是地壳中最常见的元素,石英(二氧化硅)是最常见的陶瓷和玻璃的成分,尽管在大多数情况下我们不会考虑硅是一种金属元素。化学键的类型:共价键、离子键和范德瓦耳斯键。2Theroleofmaterialsintheadvanceofcivilizationandcultureispowerfullysummarizedbythefactthatitisthenameofeachdominantnewmaterialthathasbeenusedtodescribetheculture-theStoneAge,theBronzeAge,theIronAge,andsoforth.材料在文明和文化的进步中的作用可以有力地被概括以这个的事实：每一个占主导地位的新材料的名称已经被用于描述当时的文化——石器时代,青铜时代,铁器时代,等等。3.Metallicfibers,glassfibers,andpolymerfiberscanbeformedbydrawingprocesses,Boron,carbon,andceramicsaretoobrittleandreactivetobeworkedbyconventionaldrawingprocesses.Boronfiberisproducedbychemicalvapordeposition.Carbonfiberismadebycarbonizing,orpyrolizinganorganicfilament,whichismoreeasilydrawnorspuninto,continuouslengths.Theorganicfilament,knownasaprecursorisoftenrayon,polyacrylonitrile,orapitch.金属纤维，玻璃纤维和聚合物纤维可以通过回火加工来形成，硼，碳和陶瓷由于高脆性和化学活性而不能在传统的回火加工中工作。硼纤维是通过化学气相沉积法来生产。碳纤维是通过碳化和热解有机纤维来生产的，这种方法更容易回火或者纺丝成连续的长度。这种有机纤维就是人们熟知的前驱体，通常是人造纤维，聚丙烯腈，或者是沥青。4MaterialsScienceandEngineeringformsthebedrockfortheengineeringdisciplinesbecausethestructures,components,anddevicesthatengineersdesignandusemustbemadeoutofsomething,andthatisamaterial.Thepropertiesofthematerialsthatareavailabledefineandlimitthecapabilitiesthatthedeviceorstructurecanhave,andthetechniquesthatcanbeusedtofabricateit.材料科学与工程构成了工程学科的根基，因为结构，成分，和由工程师设计和使用的设备必须由某些东西所组成，这个就是材料。材料的性能可以定义和限定为设备或结构拥有的性能，以及可以运用于制造的技术。5Themechanicalbehaviorofmaterialsisdescribedbytheirmechanicalproperties,whicharemeasuredwithidealized,simpletests.Thesetestsaredesignedtorepresentdifferenttypesofloadingconditions.Thepropertiesofamaterialreportedinvarioushandbooksaretheresultsofthesetests.Consequently,weshouldalwaysrememberthathandbookvaluesareaverageresultsobtainedfromidealizedtestsand,therefore,mustbeusedwithcare.材料的力学特性用它们的机械性质来描述，而机械性质是用理想化的，简单的测试来测量的。这些测试被设计成代表不同荷载条件的类型。被各种各样的手册记录的材料性质就是这些测试的结果。总之，我们必须记住，这些手册上的数值是从理想化的测试得出来的平均值，因此，我们必须小心使用它们。6Microstructureincludesstructureatdimensionsrangingfromtheatomsinthematerialandtheorder(orlackofit)oftheirarrangement,uptothetinygrainsofindividualcrystalsthatpacktogethertoformmostsolids,andevenuptothenearlymacroscopicleveloffibersinpaper,sandinconcrete,andthethin,multiplelayersofplastic,metal,andpaperinamicrowavepopcornbag.微观结构包括结构尺寸从材料的原子层面和它们排列的顺序（或者没有这个）到结合在一起来构成大多数固体材料的单晶的微小晶粒，甚至到纸张上的纤维，混凝土上的沙粒的接近宏观层面，以及在微波爆米花袋上的塑料，金属和纸张的薄的多层的层面。7Toughnessreferstotheabilityofmaterialstoabsorbenergybeforetheyfracture.Tensiletoughnessisequaltotheareaunderthetruestress-truestraincurve.Theimpacttoughnessismeasuredusingtheimpacttest.Thiscouldbeverydifferentfromthetensiletoughness.Fracturetoughnessdescribeshoweasilyacrackorflawinamaterialpropagates.TheplanestrainfracturetoughnessKICisacommonresultofthesetests.韧性指的是在材料断裂之前，材料所吸收能量的能力。拉伸韧性等于在真实应力与真实应变曲线下的区域。冲击韧性是用冲击实验来测量的。这和拉伸韧性十分不同。断裂韧性描述裂纹或者缺陷在材料中扩散的难易程度。平面应变断裂韧性KIC是这些实验的普遍结果。8Materialsmaybefabricatedintoobjectsinavarietyofways,includingcastingintoamold,machiningtoremoveextramaterial,joiningparts(e.g.,bysolderingorwelding),forming(forging,rolling,bending,etc.),orcompactingparticleswhicharethenfusedtogether(sintering,usedforbothmetalpowdersandmostceramics).Theseoperationsalsomodifythefinalmicrostructureandmustbetakenintoaccount.材料可能通过很多方法来制造成物体，包括铸到模具中，加工去掉多余的材料，通过焊接连接部件，通过锻造，旋转，弯曲等成型，或者压实微粒成熔融状态，例如烧结，可用在金属粉末和大多数的陶瓷。这些操作也会修饰最终的微观结构，必须加以考虑。9Whenamaterialisdesignedforagivenapplication,anumberoffactorsmustbeconsidered.Thematerialmustacquirethedesiredphysicalandmechanicalproperties,mustbecapableofbeingprocessedormanufacturedintothedesiredshape,andmustprovideaneconomicalsolutiontothedesignproblem.Satisfyingtheserequirementsinamannerthatprotectstheenvironment–perhapsbyencouragingrecyclingofthematerials–isalsoessential.当一种材料要设计成给定的用途时，很多因素必须要考虑到。这种材料必须获得想要的物理和力学性能，必须可以加工或者生产成需要的形状，和必须提供一个经济性的方案来解决设计上的困难。以保护环境的形式满足这些要求或者是通过鼓励这种材料的循环利用也是必要的。10Thepropertiesofthesevariousclassesofmaterialsareusuallyratherdistinct.Forinstance,metalsarerequiredtolightandreflective.Theyare(usually)ductile,meaningthattheycanbebentbeforetheybreak.Theyareelectricallyandthermallyconducting.Ontheotherhand,ceramicsandglassesareusuallybrittle,canbetransparenttolight,andaregoodinsulators.Theyareparticularlyusefulathightemperaturesorincorrosiveenvironments,sincetheyretaintheirproperties.Mostpolymers,ontheotherhand,cannotwithstandhightemperatures.Mostareinsulators,andmanyarehighlydeformable(whichistherealmeaningoftheword,"plastic"),andsomehaveuniqueelasticproperties(rubberbands).Semiconductors,ofcourse,aredistinguishedbytheirelectricalbehavior.Allofthesepropertycharacteristics,andthereasonstheyexist,arediscussedinsomedetailinthechaptersthatfollow.这些各种各样材料的种类的性质通常是相当明显的，例如，金属能够吸收光和反射光，它们通常是有延性的，意味着它们在断裂之前可以弯曲。它们能够导电导热。另一方面，陶瓷和玻璃通常是脆性的，可以对光透明，是良好的绝缘体。它们特别在高温或者腐蚀性的环境中使用，因为它们可以保留它们的性质。另外的，大多数的聚合物不能承受高温。大多数是绝缘体，很多是可以高度变形的（这就是“塑料”这个词的真实含义），和一些有独特的弹性性能（橡皮筋）。当然，半导体可以从它们的电学行为来区别出来。它们全部的性能特点和它们存在的原因将被在下面的章节中详细讨论。11Elastomersarethermoplasticsorlightlycross-linkedthermosetsthatexhibitgreaterthan200%elasticdeformation.Chainsareeventuallycross-linkedusingvulcanization.Thecross-linkingmakesitpossibletoobtainverylargeelasticdeformationswithoutpermanentplasticdeformation.Increasingthenumberofcross-linksincreasesthestiffnessandreducestheamountofelasticdeformationoftheelastomers.弹性体是热塑性塑料或轻度交联热固性材料,表现出弹性变形大于200%。链最终通过硫化交联。交联可以使它在没有永久塑性变形的条件下获得非常大的弹性变形。增加交叉连接的数量提高刚度和降低弹性体的弹性变形量。12Thefactorsthataffectamaterial’sresistancetocrackpropagation:AThesizeofaflawLargerflawsreducethepermittedstress.Specialmanufacturingtechniques,suchasfilteringimpuritiesfromliquidmetalsandhotpressingorhotiso-staticpressingofpowderparticlestoproduceceramicorsuperalloycomponentsreduceflawsizeandimprovefracturetoughness.BeformationabilityTheabilityofamaterialtodeformiscritical.Inductilemetals,thematerialnearthetipoftheflawcandeform,causingthetipofanycracktobecomeblunt,reducingthestressintensityfactor,andpreventinggrowthofthecrack.Increasingthestrengthofagivenmetalusuallydecreasesductilityandgivesalowerfracturetoughness.Brittlematerialssuchasceramicsandmanypolymershavemuchlowerfracturetoughnessthanmetals.CthicknessorrigidityofasampleThicker,morerigidpiecesofagivenmaterialhavealowerracturetoughnessthanthinmaterials.DstrainrateIncreasingtherateofapplicationoftheload,suchasinanimpacttest,typicallyeducesthefracturetoughnessofthematerial.EservicetemperatureIncreasingthetemperaturenormallyincreasesthefracturetoughness,justasintheimpacttest.FgrainsizeanddefectdensityAsmallgrainsizenormallyimprovesfracturetoughness,whereasmorepointdefectsanddislocationsreducefracturetoughness.Thus,afine-grainedceramicmaterialmayprovideimprovedresistancetocrackgrowth.GtensileorcompressivestressIncertainceramicmaterialswecanalsotakeadvantageofstress-inducedtransformationsthatleadtocompressivestressesthatcauseincreasedfracturetoughness.以下是影响材料抵抗裂纹扩展能力的因素：A缺陷的尺寸大的缺陷会降低许用应力。特殊的生产技术，例如从液态金属中过滤杂质，粉体颗粒通过热压或者热等静压来生产陶瓷和超耐热不锈钢的部件来减小裂纹尺寸并提高断裂韧性。B热变形温度的能力材料的变形能力是至关重要的。在韧性金属中，缺陷附近的材料可以变形，因为任何裂纹的尖端会变钝从而减小了应力强度因子，阻碍了裂纹生长。增加一个给定的金属的强度通常降低它的延展性和断裂韧性。脆性材料比如陶瓷和许多高聚物拥有比金属低得多的断裂韧性。C样品的厚度和刚度给定材料越厚，越硬，比薄的材料拥有更低的断裂韧性。D应变速率增加施加负载的速率，比如在一次冲击测试中通常降低材料的断裂韧性。E使用温度就像在冲击测试中，提高温度通常提高材料的断裂韧性。F晶粒尺寸和缺陷密度通常小的晶粒尺寸提升断裂韧性，而更多的点缺陷和位错减少断裂韧性。因此，细粒度的陶瓷材料材料可以增加断裂韧性。G拉伸或压缩应力在某些陶瓷材料中我们也可以利用提高断裂韧性的压应力所诱发的转变的优点。13Alumina(A12O3)isusedtocontainmoltenmetalorinapplicationswhereamaterialmustoperateathightemperatures,butwherehighstrengthisalsorequired.Aluminaisalsousedasalowdielectricconstantsubstrateforelectronicpackagingthathousessiliconchips.Oneclassicalapplicationisforinsulatorsinsparkplugs.Someuniqueapplicationsarealsobeingfoundindentalandmedicaluse氧化铝被用来容纳熔融金属或是材料必须在高温下工作的应用，但是高强度也是必需的。氧化铝也通常用来当做一种用于硅芯片里面的电子封装的低介电常数的基底。一种传统的运用是火花塞的绝缘体。一些独特的应用也被发现在牙科和医学运用。14Manyfactorsmustbeconsideredwhendesigningafiber-reinforcedcomposite,includingthelength,diameter,orientation,amount,andpropertiesofthefibers;thepropertiesofthematrix;andthebondingbetweenthefibersandthematrix.Fibercanbeshort,longorevencontinuous.TheirdimensionsareoftencharacterizedbytheaspectratioI/d,whereIisthefiberlengthanddisthediameter.Typicalfibershavediametersvaryingfrom10mm(10x10-4cm)to150mm(150x10-4cm).当设计纤维增强复合材料时，许多因素都必须要考虑到，这包括纤维的长度、直径、取向、数量和性能；基底的性能；以及纤维和基底之间的键合作用。纤维可以很短，很长甚至是连续的。他们的尺寸通常以I/d来表征，I指纤维的长度，d指直径。典型的纤维有直径范围从10微米((10x10-4cm)到150微米(150x10*4)。15.Theimpacttestdescribestheresponseofamaterialtoarapidlyappliedload.TheCharpyandIzodtestsaretypical.Theenergyrequiredtofracturethespecimenismeasuredandcanbeusedasthebasisforcomparisonofvariousmaterialstestedunderthesameconditions.Inaddition,atransitiontemperatureabovewhichthematerialfailsinaductile,ratherthanabrittle,mannercanbedetermined.材料的冲击试验描述了迅速外加负载材料的反应。简支梁和悬臂梁测试是经典的。断裂试样所需的能量被测量并且被用来当做在相同条件下各种材料测试比较的基础。此外，转变温度高于材料的韧性失效,而不是脆的,可以确定。16Examinationofthefracturesurfaceatahighmagnification-perhapsusingascanningelectronmicroscoperevealsadimpledsurface.Thedimplesaretracesofthemicrovoidsproducedduringfracture.Normally,thesemicrovoidsareround,orequiaxed,whenanormallytensilestressproducesthefailure,However,ontheshearlipthedimplesareoval-shaped,orelongated,withtheovals,pointingtowardtheoriginofthefracture.用扫描电镜在设定的高放大率下观察到的断裂表面是一个酒窝形表面，这些酒窝是在断裂中产生的微孔的痕迹。通常情况下，这些微孔是圆的或者各向等大的，然而当一个正常拉应力导致失效时，在切变裂痕处的酒窝是椭圆状的或者瘦长的，并且椭圆朝向断裂起源处。Thestrengthofceramicsandglassdependsupontheprobabilityoffindingaflawthatexceedsacertaincriticalsize.Forlargecomponentsorlargerfibersthisprobabilityincreases.Asaresult,thestrengthoflargercomponentsandfibersislikelytobelowerthanthatofsmallercomponentsorshorterfibers.陶瓷和玻璃的强度由它们的最大裂纹决定，对大型元件或长纤维来说这很可能增加。结果，大型元件和长纤维的强度低于拥有相同结构的小型元件和短纤维18.Inmaterialsscience,theemphasisisontheunderlyingrelationshipsbetweenthesynthesisandprocessing,structure,andpropertiesofmaterials.Inmaterialsengineering,thefocusisonhowtotranslateortransformmaterialsintoausefuldeviceorstructure.在材料科学中，重点在于研究合成和加工、材料的结构和性能之间潜在关系。在材料工程中，重点在于研究如何把材料转化或改造成有用的设备或结构19Fractureinfiber-reinforcedcompositematerialsismorecomplex,Typically,thesecompositescontainstrong,brittlefiberssurroundedbyasoft,ductilematrix,asinboron-reinforcedaluminum.Whenatensilestressisappliedalongthefibers,thesoftAluminumdeformsinaductilemanner,withvoidformationandcoalescenceeventuallyproducingadimpledfracturesurface.Asthealuminumdeforms,theloadisnolongertransmittedeffectivelytotilefibers;thefibersbreakinabrittlemanneruntiltherearetoofewofthemleftintacttosupportthefinalload.在纤维增强复合材料中的断裂更加复杂，通常，这些复合物中包含由软的延性基体环绕的硬的脆性纤维，就像在硼增强铝基复合材料中一样。当一个伸长应力作用独自作用在纤维上时，软的铝发生延性变形，孔隙和接合处逐渐产生一个酒窝形断裂表面。由于铝变形，负载就不能有效传送到纤维上，直到完整的纤维太少以致不能支撑最终负载时纤维会发生脆性断裂。20Onewayistodefineceramicsbasedontheirclassofchemicalcompounds(e.g.,oxides,carbides,nitride,sulfides,etc.).Anotherwaywhichwewillusehereistoclassifyceramicsbytheirmajorfunction(Table4-1).Ceramicsareusedinawiderangeoftechnologiessuchasrefractories,sparkplugs,dielectricsincapacitors,sensors,abrasives,magneticrecordingmedia,etc.Thespaceshuttlemakesuseof~25,000reusable,light-weight,highlyporousceramictilesthatprotectthealuminumframefromtheheatgeneratedduringre-entryintotheEarth’satmosphere.定义陶瓷的一种方法是根据他们的化合物种类（例如氧化物、碳化物、氮化物、硫化物等）。我们将在这使用的另一种方法是通过他们的主要功能来分类陶瓷。陶瓷应用于很宽的技术领域，比如耐火材料、火花塞、电容器的绝缘体、传感器、耐磨材料、磁记录介质等。21FiberlengthanddiameterFibercanbeshort,longorevencontinuous.TheirdimensionsareoftencharacterizedbytheaspectratioI/d,whereIisthefiberlengthanddisthediameter.纤维可以是短的、长的或者甚至是连续不断的。他们的尺寸特征表现在I/d比，I是纤维长度，d是直径。Typicalfibershavediametersvaryingfrom10mm(10x10-4cm)to150mm(150x10-4cm).典型纤维的直径在10mm到150mm变化范围内Thestrengthofacompositeimproveswhentheaspectratioislarge.Fibersoftenfracturebecauseofsurfaceimperfections.Makingthediameterassmallaspossiblegivesthefiberlesssurfacearea,andconsequently,fewerflawsmightpropagate.AmountofFiberAgreatervolumefractionoffibersincreasesthestre