材料科学与工程专业英语课文自己整理的 可以打印匡少平 王世颖 第二版 化学工业出版社.docx

材料科学与工程专业英语课文自己整理的 可以打印匡少平 王世颖 第二版 化学工业出版社.docx

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材料科学与工程专业英语课文自己整理的可以打印匡少平王世颖第二版化学工业出版社

Unit1

Materialsareprobablymoredeep-seatedinourculturethanmostofusrealize.Transportation,housing,clothing,communication,recreation,andfoodproduction—virtuallyeverysegmentofoureverydaylivesisinfluencedtoonedegreeoranotherbymaterials.Historically,thedevelopmentandadvancementofsocietieshavebeenintimatelytiedtothemembers’abilitytoproduceandmanipulatematerialstofilltheirneeds.Infact,earlycivilizationshavebeendesignatedbytheleveloftheirmaterialsdevelopment（StoneAge,BronzeAge,IronAge）.1

Theearliesthumanshadaccesstoonlyaverylimitednumberofmaterials,thosethatoccurnaturally:

stone,wood,clay,skins,andsoon.Withtimetheydiscoveredtechniquesforproducingmaterialsthathadpropertiessuperiortothoseofthenaturalones;thesenewmaterialsincludedpotteryandvariousmetals.Furthermore,itwasdiscoveredthatthepropertiesofamaterialcouldbealteredbyheattreatmentsandbytheadditionofothersubstances.Atthispoint,materialsutilizationwastotallyaselectionprocessthatinvolveddecidingfromagiven,ratherlimitedsetofmaterialstheonebestsuitedforanapplicationbyvirtueofitscharacteristics.Itwasnotuntilrelativelyrecenttimesthatscientistscametounderstandtherelationshipsbetweenthestructuralelementsofmaterialsandtheirproperties.Thisknowledge,acquiredoverapproximatelythepast100years,hasempoweredthemtofashion,toalargedegree,thecharacteristicsofmaterials.Thus,tensofthousandsofdifferentmaterialshaveevolvedwithratherspecializedcharacteristicsthatmeettheneedsofourmodernandcomplexsociety;theseincludemetals,plastics,glasses,andfibers.

Thedevelopmentofmanytechnologiesthatmakeourexistencesocomfortablehasbeenintimatelyassociatedwiththeaccessibilityofsuitablematerials.Anadvancementintheunderstandingofamaterialtypeisoftentheforerunnertothestepwiseprogressionofatechnology.Forexample,automobileswouldnothavebeenpossiblewithouttheavailabilityofinexpensivesteelorsomeothercomparablesubstitute.Inourcontemporaryera,sophisticatedelectronicdevicesrelyoncomponentsthataremadefromwhatarecalledsemiconductingmaterials.

MATERIALSSCIENCEANDENGINEERING

Sometimesitisusefultosubdividethedisciplineofmaterialsscienceandengineeringintomaterialsscienceandmaterialsengineeringsubdisciplines.Strictlyspeaking,“materialsscience”involvesinvestigatingtherelationshipsthatexistbetweenthestructuresandpropertiesofmaterials.Incontrast,“materialsengineering”is,onthebasisofthesestructure–propertycorrelations,designingorengineeringthestructureofamaterialtoproduceapredeterminedsetofproperties.2Fromafunctionalperspective,theroleofamaterialsscientististodeveloporsynthesizenewmaterials,whereasamaterialsengineeriscalledupontocreatenewproductsorsystemsusingexistingmaterials,and/ortodeveloptechniquesforprocessingmaterials.Mostgraduatesinmaterialsprogramsaretrainedtobebothmaterialsscientistsandmaterialsengineers.

“Structure”isatthispointanebuloustermthatdeservessomeexplanation.Inbrief,thestructureofamaterialusuallyrelatestothearrangementofitsinternalcomponents.Subatomicstructureinvolveselectronswithintheindividualatomsandinteractionswiththeirnuclei.Onanatomiclevel,structureencompassestheorganizationofatomsormoleculesrelativetooneanother.Thenextlargerstructuralrealm,whichcontainslargegroupsofatomsthatarenormallyagglomeratedtogether,istermed“microscopic,”meaningthatwhichissubjecttodirectobservationusingsometypeofmicroscope.Finally,structuralelementsthatmaybeviewedwiththenakedeyearetermed“macroscopic.”

Thenotionof“property”deserveselaboration.Whileinserviceuse,allmaterialsareexposedtoexternalstimulithatevokesometypeofresponse.Forexample,aspecimensubjectedtoforceswillexperiencedeformation,orapolishedmetalsurfacewillreflectlight.Apropertyisamaterialtraitintermsofthekindandmagnitudeofresponsetoaspecificimposedstimulus.Generally,definitionsofpropertiesaremadeindependentofmaterialshapeandsize.

Virtuallyallimportantpropertiesofsolidmaterialsmaybegroupedintosixdifferentcategories:

mechanical,electrical,thermal,magnetic,optical,anddeteriorative.Foreachthereisacharacteristictypeofstimuluscapableofprovokingdifferentresponses.Mechanicalpropertiesrelatedeformationtoanappliedloadorforce;examplesincludeelasticmodulusandstrength.Forelectricalproperties,suchaselectricalconductivityanddielectricconstant,thestimulusisanelectricfield.Thethermalbehaviorofsolidscanberepresentedintermsofheatcapacityandthermalconductivity.Magneticpropertiesdemonstratetheresponseofamaterialtotheapplicationofamagneticfield.Foropticalproperties,thestimulusiselectromagneticorlightradiation;indexofrefractionandreflectivityarerepresentativeopticalproperties.Finally,deteriorativecharacteristicsrelatetothechemicalreactivityofmaterials.Thechaptersthatfollowdiscusspropertiesthatfallwithineachofthesesixclassifications.

Inadditiontostructureandproperties,twootherimportantcomponentsareinvolvedinthescienceandengineeringofmaterials—namely,“processing”and“performance.“Withregardtotherelationshipsofthesefourcomponents,thestructureofamaterialwilldependonhowitisprocessed.Furthermore,amaterial’sperformancewillbeafunctionofitsproperties.Thus,theinterrelationshipbetweenprocessing,structure,properties,andperformanceisasdepictedintheschematicillustrationshowninFigure1.1.Throughoutthistextwedrawattentiontotherelationshipsamongthesefourcomponentsintermsofthedesign,production,andutilizationofmaterials

WHYSTUDYMATERIALSSCIENCEANDENGINEERING?

Whydowestudymaterials?

Manyanappliedscientistorengineer,whethermechanical,civil,chemical,orelectrical,willatonetimeoranotherbeexposedtoadesignprobleminvolvingmaterials.Examplesmightincludeatransmissiongear,thesuperstructureforabuilding,anoilrefinerycomponent,oranintegratedcircuitchip.Ofcourse,materialsscientistsandengineersarespecialistswhoaretotallyinvolvedintheinvestigationanddesignofmaterials.

Manytimes,amaterialsproblemisoneofselectingtherightmaterialfromthemanythousandsthatareavailable.Thereareseveralcriteriaonwhichthefinaldecisionisnormallybased.Firstofall,thein-serviceconditionsmustbecharacterized,forthesewilldictatethepropertiesrequiredofthematerial.Ononlyrareoccasionsdoesamaterialpossessthemaximumoridealcombinationofproperties.Thus,itmaybenecessarytotradeoffonecharacteristicforanother.Theclassicexampleinvolvesstrengthandductility;normally,amaterialhavingahighstrengthwillhaveonlyalimitedductility.Insuchcasesareasonablecompromisebetweentwoormorepropertiesmaybenecessary.

Asecondselectionconsiderationisanydeteriorationofmaterialpropertiesthatmayoccurduringserviceoperation.Forexample,significantreductionsinmechanicalstrengthmayresultfromexposuretoelevatedtemperaturesorcorrosiveenvironments.Finally,probablytheoverridingconsiderationisthatofeconomics:

Whatwillthefinishedproductcost?

Amaterialmaybefoundthathastheidealsetofpropertiesbutisprohibitivelyexpensive.Hereagain,somecompromiseisinevitable.Thecostofafinishedpiecealsoincludesanyexpenseincurredduringfabricationtoproducethedesiredshape.

Themorefamiliaranengineerorscientistiswiththevariouscharacteristicsandstructure–propertyrelationships,aswellasprocessingtechniquesofmaterials,themoreproficientandconfidentheorshewillbetomakejudiciousmaterialschoicesbasedonthesecriteria.

Unit2

CLASSIFICATIONOFMATERIALS

Solidmaterialshavebeenconvenientlygroupedintothreebasicclassifications:

metals,ceramics,andpolymers.Thisschemeisbasedprimarilyonchemicalmakeupanatomicstructure,andmostmaterialsfallintoonedistinctgroupingoranother,althoughtherearesomeintermediates.Inaddition,therearethecomposites,combinationsoftwoormoreoftheabovethreebasicmaterialclasses.Anotherclassificationisadvancedmaterials—thoseusedinhigh-technologyapplications—viz.semiconductors,biomaterials,smartmaterials,andnanoengineeredmaterials;

Metals

Materialsinthisgrouparecomposedofoneormoremetallicelements（suchasiron,aluminum,copper,titanium,gold,andnickel）,andoftenalsononmetallicelements（forexample,carbon,nitrogen,andoxygen）inrelativelysmallamounts.3Atomsinmetalsandtheiralloysarearrangedinaveryorderlymanner（asdiscussedinChapter3）,andincomparisontotheceramicsandpolymers,arerelativelydense（Figure1.3）.Withregardtomechanicalcharacteristics,thesematerialsarerelativelystiff（Figure1.4）andstrong（Figure1.5）,yetareductile（i.e.,capableoflargeamountsofdeformationwithoutfracture）,andareresistanttofracture（Figure1.6）,whichaccountsfortheirwidespreaduseinstructuralapplications.Metallicmaterialshavelargenumbersofnonlocalizedelectrons;thatis,theseelectronsarenotboundtoparticularatoms.Manypropertiesofmetalsaredirectlyattributabletotheseelectrons.Forexample,metalsareextremelygoodconductorsofelectricity（Figure1.7）andheat,andarenottransparenttovisiblelight;apolishedmetalsurfacehasalustrousappearance.Inaddition,someof