材料科学与工程专业英语课件

HubeiUniversityofAutomotiveTechnologySpecialtyEnglish

1、语法较为简单，多用被动语态，从句等。2、专有名词多，有规律可循（构词法）（读音较为复杂，无规律）3、写作要求清晰明了如何学习？（1）记忆常见科技词汇（构词法）（2）多阅读科技文章，学习如何用英语表达。避免自创的新奇语句。（3）课后练习翻译，写作（Practicemakesperfect.）★CharacteristicsofSpecialtyEnglishChapter1

MaterialsandHeatTreatment◆

ReadingandanswerquestionsThenewwordsyoumaybemeet:

metallic金属的corrosion腐蚀ductile延展ballbearing滚珠轴承multiphase多相wrought加工的，精细的malleable可锻的有延展性的FerrousAlloysArbitrary专横的，独断的，任意的Smelt熔炼，精炼Intricate复杂的，精巧的Combination结合，合并，化合物FerrousAlloysMorethan90%byweightofthemetallicmaterialsusedbyhumanbeingsareferrousalloys.Thisrepresentsanimmensefamilyofengineeringmaterialswithawiderangeofmicrostructureandrelatedproperties.FerrousAlloysThemajorityofengineeringdesignsthatrequirestructuralloadsupportorpowertransmissioninvolveferrousalloys.asapracticalmatter,thesealloysfallintotwobroadcategoriesbasedonthecarboninthealloycomposition.FerrousAlloysSteelgenerallycontainsbetween0.05wand2.0wcarbon.Thecastironsgenerallycontainbetween2.0wand4.5wcarbon.

Withinthesteelcategory,weshalldistinguishwhetherornotasignificantamountofalloyingelementsotherthancarbonisused.

对于钢的区分，我们要弄清楚的是是否含有有效量的合金元素而不是碳的含量。

FerrousAlloysFerrousAlloysAcompositionof5wtotalnoncarbonadditionswillserveasanarbitraryboundarybetweenlowalloyandhighalloysteels.FerrousAlloysThesealloyadditionsarechosencarefullybecausetheyinvariablybringwiththemsharplyincreasedmaterialcosts.

TheyarejustifiedonlybyessentialimprovementsinpropertiessuchashigherstrengthorimprovedcorrosionresistancequestionsHowdoyoudistinguishsteelfromcastiron?Howdoyoudistinguishlowalloysteelfromhighalloysteel?1.1.1IronandSteelTheearthcontainsalargenumberofmetalswhichareusefultoman.Oneofthemostimportantoftheseisiron.Modernindustryneedsconsiderablequantitiesofthismetal,eitherintheformofironorintheformofsteel.1.1.1IronandSteelAcertainnumberofnon-ferrousmetals,includingaluminumandzinc,arealsoimportant,buteventodaythemajorityofourengineeringproductsareofironorsteel.Moreover,ironpossessesmagneticproperties,whichhavemadethedevelopmentofelectricalpowerpossible.1.1.1IronandSteelTheironorewhichwefindonearthisnotpure.Itcontainssomeimpuritiesthatmustberemovedbysmelting.Theprocessofsmeltingconsistsofheatingtheoreinablastfurnacewithcokeandlimestone,andreducingittometal.Blastsofhotairenterthefurnacefromthebottomandprovidetheoxygenthatisnecessaryforthereductionoftheore.1.1.1IronandSteelTheorebecomesmolten,anditsoxidescombinewithcarbonfromthecoke.Thenon-metallicconstituentsoftheorecombinewiththelimestonetoformaliquidslag.Thisfloatsontopofthemolteniron,andpassedoutofthefurnacethroughatap.Themetalwhichremainsispigiron.1.1.1IronandSteelWecanmeltthisdownagaininanotherfurnace-acupola-withmorecokeandlimestone,andtapitoutintoaladleordirectlyintomolds.Thisiscastiron.Castirondoesnothavethestrengthofsteel.Itisbrittleandmayfractureundertension.1.1.1IronandSteelButitpossessescertainpropertiesthatmakeitveryusefulinthemanufactureofmachinery.Inthemoltenstateitisveryfluid,therefore,itiseasytocastitintointricateshapes.Alsoitiseasytomachineit.Castironcontainssmallproportionofothersubstances.1.1.1IronandSteelThesenon-metallicconstituentsofcastironincludecarbon,siliconandsulphur,andthepresenceofthesesubstancesaffectsthebehaviorofthemetal.Ironwhichcontainsanegligiblequantityofcarbon,forexample,wroughtironbehavesdifferentlyfromironwhichcontainsalotofcarbon.1.1.1IronandSteelThecarbonincastironispresentpartlyasfreegraphiteandpartlyasachemicalcombinationofironandcarbonwhichiscalledcementite.Thisisaveryhardsubstance,anditmakestheironhardtoo.1.1.1IronandSteelHowever,ironcanonlyholdabout1.5%ofcementite.Anycarboncontentabovethatpercentageispresentoftheformofaflakygraphite.1.1.1IronandSteelSteelcontainsnofreegraphite,anditscarboncontentrangesfromalmostnothingto1.5%.Wemakewireandtubingfrommildsteelwithaverylowcarboncontent,anddrillsandcuttingtoolsfromhighcarbonsteel.questionsHowisthesteelmade?Ifyouwanttohaveahighstrengthironbasedmaterial,whatshouldyoudo?Whatisthefunctionofthecokewhenproducingpigiron?Whatisthedifferencebetweenthepigironandthecastiron?1.1.2CarbonandlowalloysteelThemajorityofferrousalloysbelongstothiscategory.Thereasonsforthisarestraightforward.Theyaremoderatelypricedduetotheabsenceoflargeamountsofalloyingelements,andtheyaresufficientlyductiletobereadilyformed.Thefinalproductisstronganddurable.Theseeminentlypracticalmaterialsfindapplicationfromballbearingstometalsheetformedintoautomobilebodies.Forexample,the10XX,11XX,12XX,15XXetc.(AISIstandards,inwhichthefirsttwonumbersgiveacodedesignatingthetypeofalloyadditionsandthelasttwoorthreenumbersgivethecarboncontentinhundredthsofaweightpercent).1.1.2CarbonandLowSteelAsanexample,theplaincarbonsteelwith0.40wcarbonisa1040steel,whereasasteelwith1.45wCrand1.5wcarbonisa52150steel.1.1.2CarbonandLowSteelOneshouldkeepinmindthatchemicalcompositionsquotedinalloydesignationsareapproximateandwillvaryslightlyfromproducttoproductwithinacceptablelimitsofindustrialqualitycontrol.1.1.2CarbonandLowSteelAninterestingclassofalloysknownashighstrengthlowalloy(HSLA)steelshasemergedinresponsetorequirementsforweightreductionofvehicles.1.1.2CarbonandLowSteelThecompositionsofmanycommercialHSLAsteelsareproprietaryandspecifiedbymechanicalpropertiesratherthancomposition.Butatypicalexamplemightcontain0.2wcarbonandabout1.0worlessofsuchelementsasMn,P,Si,Cr,Ni,orMo.1.1.2CarbonandLowSteel1.1.2CarbonandLowSteelThehighstrengthofHSLAsteelsistheresultofoptimalalloyselectionandcarefullycontrolledprocessingsuchashotrolling(deformationattemperaturessufficientlyelevatedtoallowsomestressrelief)questionWhatisthedifferencebetweenthecarbonsteelandHSLAsteel?WhytheHSLAsteelissopopular?HowarethegoodpropertiesoftheHSLAsteelsobtained?vocabularyDuctile延展Durable耐久的Quote引用援引Eminently杰出地Rust生锈Precipitation沉淀沉积Dislocation位错1.1.3HighAlloySteelAsmentionedabove,alloyadditionsmustbewithcareandjustificationbecausetheyareexpensive.Weshallnowlookatthreecasesinwhichengineeringdesignrequirementsjustifyhighalloycomposition(i.e.,totalnon-carbonadditionsgreaterthan5w).1.1.3HighAlloySteelStainlesssteelsrequirealloyadditionstopreventdamagefromacorrosiveatmosphere.Toolsteelsrequirealloyadditionstoobtainsufficienthardnessformachiningapplication..1.1.3HighAlloySteelSoitiscalled“superalloys”whichrequirealloyadditionstoprovidestabilityinhightemperatureapplicationssuchasturbineblades.1.1.3HighAlloySteelStainlesssteelsaremoreresistanttorustingandstainingthancarbonandlowalloysteels,dueprimarilytothepresenceofchromiumaddition.1.1.3HighAlloySteelTheamountofchromiumisatleast4wandusuallyabove10w.Levelsashighas30wCraresometimesused.Theausteniticstainlesssteelshavetheaustenitestructureretainedatroomtemperature.1.1.3HighAlloySteelTheaustenitehasthefccstructureandisstableabove910℃.Thisstructurecanoccuratroomtemperaturewhenitisstabilizedbyanappropriatealloyadditionsuchasnickel.1.1.3HighAlloySteelWithoutthehighnickelcontent,thebccstructureisstable,asseenintheferriticstainlesssteels.Formanyapplicationsnotrequiringthehighcorrosionresistanceofausteniticstainlesssteels,theseloweralloy(andlessexpensive)ferriticstainlesssteelsarequiteserviceable.1.1.3HighAlloySteelArapidquenchheattreatmentdiscussedlaterallowstheformationofamorecomplexbodycenteredtetragonalcrystalstructurecalledmartensite.Thiscrystalstructureyieldshighstrengthandlowductility.1.1.3HighAlloySteelAsaresult,thesemartensiticstainlesssteelsareexcellentforapplicationssuchascutleryandsprings.Precipitationhardeningisanotherheattreatment.1.1.3HighAlloySteelEssentially,itinvolvesproducingamultiphasemicrostructurefromasinglephaseone.Theresultisincreasedresistancetodislocationmotionand,thereby,greaterstrengthorhardness.Precipitationhardeningstainlesssteelscanbefoundinapplicationssuchascorrosionresistantstructuralmembers.1.1.3HighAlloySteelToolsteelsareusedforcutting,formingorotherwiseshapinganothermaterial.Plaincarbonsteelcanalsobetoolsteel.Forshapingoperationsthatarenottoodemanding,suchamaterialisadequate.1.1.3HighAlloySteelInfact,toolsteelswerehistoricallyoftheplaincarbonvarietyuntilthemid-nineteenthcentury.Nowhighalloyadditionsarecommon.Theiradvantageisthattheycanprovidethenecessaryhardnesswithsimpleheattreatmentsandretainthathardnessathigheroperatingtemperature.1.1.3HighAlloySteelTheprimaryalloyingelementsusedinthesematerialsaretungsten,molybdenum,andchromium.1.1.3HighAlloySteelThetermsuperalloysreferstoabroadclassofmetalwithespeciallyhighstrengthatelevatedtemperatures(evenabove1000℃).Manystainlesssteelsserveadualroleasheatresistantalloys.Exceptironbasedsuperalloys,therearealsocobaltandnickelbasedalloys.1.1.3HighAlloySteelMostsuperalloyscontainchromiumadditionsforoxidationandcorrosionresistance.Thesematerialsareexpensiveand,insomecases,extremelyso.Buttheincreasinglysevererequirementsofmoderntechnologyarejustifyingsuchcosts.1.1.3HighAlloySteelBetween1950and1980,theuseofsuperalloysinaircraftturbojetenginesrosefrom10%to50%byweight.Atthispoint,ourdiscussionofsteelshastakenusintocloselyrelatedtonon-ferrousalloys.1.1.3HighAlloySteelBeforegoingontothegeneralareaofallothernon-ferrousalloys,wemustdiscussthetraditionalandimportantferroussystem,thecastirons.questionsGenerallyspeaking,whatistheroleoftheelementssuchaschromium,nickelandtungsteninthehighalloysteel?Whatisthemainpropertyofthesuperalloysteel?Byaddingwhatelementsintosteelcanweobtainausteniteatroomtemperature?1.1.4CastironsAsstatedearlier,wedefinecastironsastheferrousalloyswithgreaterthan2wcarbon.Theyalsogenerallycontainupto3wsiliconforcontrolofcarbideformationkinetics.1.1.4CastironsCastironshaverelativelylowmeltingtemperaturesandliquidphaseviscosities,donotformundesirablesurfacefilmswhenpoured,andundergomoderateshrinkageduringsolidificationandcooling.1.1.4CastironsThecastironsmustbalancegoodformabilityofcomplexshapesagainstinferiormechanicalpropertiescomparedtowroughtalloys.Acastironisformedintoafinalshapebypouringmoltenmetalintoamold.Theshapeofthemoldisretainedbythesolidifiedmetal.Inferiormechanicalpropertiesresultfromalessuniformmicrostructure,includingsomeporosity.

1.1.4CastironsWroughtalloysareinitiallycastbutarerolledorforgedintofinal,relativelysimpleshapes(infact,“wrought”simplymeans“worked”)1.1.4CastironsTherearefourgeneraltypesofcastirons.Whiteironhasacharacteristicwhite,crystallinefracturesurface.LargeamountsofFe3Careformedduringcasting,givingahard,brittlematerial.1.1.4CastironsGrayironhasagrayfracturesurfacewithafinelyfacetedstructure.Asignificantsiliconcontent(2wto3w)promotesgraphite(C)precipitationratherthancementite(Fe3C).1.1.4CastironsThesharp,pointedgraphiteflakescontributetocharacteristicbrittlenessingrayiron.Byaddingasmallamount(0.05w)ofmagnesiumtothemoltenmetalofthegrayironcomposition,spheroidalgraphiteprecipitatesratherthanflakesareproduced.1.1.4CastironsThisresultingductileironderivesitsnamefromtheimprovedmechanicalproperties.Ductilityisincreasedbyafactorof20,andstrengthisdoubled.1.1.4CastironsAmoretraditionalformofcastironwithreasonableductilityismalleableiron,whichisfirstcastaswhiteironandthenheattreatedtoproducenodulargraphiteprecipitates.1.1.4CastironsThename“castiron”derivesfromthefactthatthereisonlyironincastirons(T/F)Howismalleablecastironobtained?Whatisthefunctionoftheelementofmagnesiumwhenitisaddedintothecastiron?questions1.2HeatTreatmentofSteelWecanalterthecharacteristicsofsteelinvariousways.Inthefirstplace,steelwhichcontainsverylittlecarbonwillbemilderthansteelwhichcontainsahigherpercentageofcarbon,uptothelimitofabout1.5%.1.2HeatTreatmentofSteelSecondly,wecanheatthesteelaboveacertaincriticaltemperature,andthenallowittocoolatdifferentrates,Atthiscriticaltemperature,changesbegintotakeplaceinthemolecularstructureofthemetal.1.2HeatTreatmentofSteelIntheprocessknownasannealing,weheatthesteelabovethecriticaltemperatureandpermitittocoolveryslowly.Thiscausesthemetalsofterthanbefore,andmucheasiertobemachined.1.2HeatTreatmentofSteelAnnealinghasasecondadvantage,ithelpstorelieveanyinternalstresseswhichexistinthemetal.Thesestressesareliabletooccurthroughharmmeringorworkingthemetal,orthroughrapidcooling.1.2HeatTreatmentofSteelMetalwhichwecausetocoolrapidlycontractsmorerapidlyontheoutsidethanontheinside.Thisproducesunequalcontractions,whichmaygiverisetodistortionorcracking.Metalwhichcoolsslowlyislessliabletohavetheseinternalstressesthanmetalwhichcoolsquickly.1.2HeatTreatmentofSteelOntheotherhand,wecanmakesteelharderbyrapidcooling.Weheatitupbeyondthecriticaltemperature,andthenquenchitinwaterorsomeotherliquid.1.2HeatTreatmentofSteelTherapidtemperaturedropfixesthestructuralchangeinthesteelandthishardenedsteelismoreliabletofracturethannormalsteel.Wethereforeheatitagaintoatemperaturebelowthecriticaltemperature,andcoolitslowly.Thistreatmentiscalledtempering1.2HeatTreatmentofSteel.Ithelpstorelievetheinternalstresses,andmakesthesteellessbrittlethanbefore.Thepropertiesoftemperedsteelenableustouseitinthemanufactureoftoolswhichneedafairlyhardsteel.Highcarbonsteelisharderthantemperedsteel,butitismuchmoredifficulttowork.1.2HeatTreatmentofSteelTheseheattreatmentstakeplaceduringthevariousshapingoperations.Wecanobtainbarsandsheetsofsteelbyrollingthemetalthroughhugerollsinarollingmill.Therollpressuresmustbegreaterforcoldrollingthanforhotrolling,butcoldrollingenablestheoperatorstoproducerollsofgreataccuracyanduniformity,andwithabettersurfacefinish.1.2HeatTreatmentofSteelOthershapingoperationsincludedrawingintowire,castinginmolds,andforging.questionsIfaworkpiecemadeofsteelistoohardtowork,whatwouldyoudo?Generallyspeaking,whatkindofsteelissofter,andwhatkindisharder?Ifyouwantapieceofsteeltobeharderorsofter,whatwouldyoudo?1.3PrincipleofHeatTreatmentofSteelTheoreticalstudyofheattreatmentsteelwasinitiatedbythediscoveryofthecriticalpointsinsteelmadebyD.K.Chernovin1868.Chernov’sassumptionthatthepropertiesofsteelsaredeterminedbythestructureandthatthelatterdependsontheheatingtemperatureandrateofcoolinghasbeengenerallyrecognized.1.3PrincipleofHeatTreatmentofSteelDuringthedecadeswhichfollowedtheresearcherswereengagedinestablishingtherelationshipsbetweenthestructureandconditionsofitsformation(mainlytheheatingtemperatureandcoolingrate)1.3PrincipleofHeatTreatmentofSteelTheprincipalachievementsinthetheoryofheattreatmentwere,however,madein1920’sand1930’s.1.3PrincipleofHeatTreatmentofSteelMetallurgistshavegraduallycometotheconclusionthatthetypeofstructure(itstexture,properties,etc.)isdeterminedbythetemperatureofitsformation.1.3PrincipleofHeatTreatmentofSteelIthasbecomeclearthattheprocessesoccuringinheattreatmentcanbeexplainedbystudyingthekineticsoftransformationsatvarioustemperaturesandthefactorsaffectingthekinetics.1.3PrincipleofHeatTreatmentofSteelTheseconceptsformedthebasisofextensiveexperimentalworkundertakenbyS.S.Steinbergandcoworkersin1930~1940.Theycollectedavastexperimentalmaterialwhichhasconstitutedthebasisofthemodernconceptsontransformationsinsteelandthetheoryofheattreatmentofsteel.1.3PrincipleofHeatTreatmentofSteelStudiesinthesamedirectionwerestartedbymanyresearchersinothercountriesatthesametimeorsomewhatlater.Amongthepioneersinthisfield,thenamesofR.F.MehlandE.C.Bain(USA),andF.Wever,H.Esser,and

H.Hannemann(Germany)shouldbementionedfirst;1.3PrincipleofHeatTreatmentofSteeltheycarriedoutnumerousanddetailedstudiesintothekineticsoftransformationsinvarioussteels.ThenatureofhardenedsteelcouldonlybeexaminedbyusingXraysandothermethodsofphysicalanalysisofmetals(electronmicroscopy,internalfriction,etc)1.3PrincipleofHeatTreatmentofSteelNumerousworksofG.V.Kurdymovandhisfollowers,anumberofotherforeignmetallophysicistshaverevealedimportantpeculiaritiesinthefinestructureofsteel.1.3PrincipleofHeatTreatmentofSteelthetheoryofheattreatmentofsteelisunderstoodastheanalysisoftheprocessesofstructureformation(ontransformations)andtheparticularitiesofstructuralstateofalloys(innon-equilibrium).1.3PrincipleofHeatTreatmentofSteelHerethetheoryofheattreatmentofsteel,basedonthegeneraltheoryofphasetransformationsinundercooledsystemswillbediscussed.questionsWhoisthefirstmetallurgistwhosuggestedthatthepropertiesofsteelweredeterminedbythestructure?Whataretheimportantfactorsaffectingthestructureofsteelduringheattreatmentprocess?1.4Non-ferrousAlloysAlthoughferrousalloysareusedinthemajorityofmetallicapplicationsincurrentengineeringdesigns,non-ferrousalloysplayalargeandindispensableroleinourtechnology.SurfacecoatingSurfacecoatingaremixturesoffilmformingmaterialspluspigment,solvents,andotheradditives,which,whenappliedtoasurfaceandcuredordried,yieldathinfilmthatisfunctionalandoftendecorative.Theyincludepaints,dryingoilsandvarnishes,syntheticclearcoatings,andotherproductswhoseprimaryfunctionistoprotectthesurfaceofanobjectfromtheenvironment.Theseproductscanalsoenhancetheaestheticappealofanobjectbyaccentuatingitssurfacefeaturesorevenbyconcealingthemfromview.Mostsurfacecoatingsemployedinindustryandbyconsumersarebasedonsyntheticpolymers-thatis,industriallyproducedsubstancescomposedofextremelylarge,ofteninterconnectedmoleculesthatformtough,flexible,adhesivefilmswhenappliedtosurfaces.Theothercomponentmaterialsofsurfacecoatingarepigments,whichprovidecolour,opacity,gloss,andotherproperties;solventsorcarrierliquids,whichprovidealiquidmediumforapplyingthefilmformingingredients;andadditives,whichprovideanumberofspecialproperties.1.4Non-ferrousAlloysAsforferrousalloys,thelistofnon-ferrousalloysis,ofcourse,longandcomplex.Weshallbrieflylistthemajorfamiliesofnon-ferrousalloysandtheirkeyattributes.1.4Non-ferrousAlloysAluminumalloysarebestknownforlowdensityandcorrosionresistance.Electricalconductivity,easeoffabrication,andappearancearealsoattractivefeatures.1.4Non-ferrousAlloysBecauseofthese,theworldproductionofaluminumroughlydoubledinonerecent10yearperiod.Orereservesforaluminumarelarge(representing8%oftheerath’scrust)andaluminumcanbeeasilyrecycled.1.4Non-ferrousAlloysMagnesiumalloyshaveevenlowerdensitythanaluminumand,asaresult,appearinnumerousstructuralapplicationssuchasaerospacedesigns.1.4Non-ferrousAlloysAluminumisafccmaterialandthereforehasnumerousslipsystems,leadingtogoodductility.Bycontrast,magnesiumishcpwithonlythreeslipsystemsandcharacteristicbrittleness.1.4Non-ferrousAlloysTitaniumalloyshavebecomewidelyusedsinceWorldWarⅡ.Beforethattime,apracticalmethodofseparatingtitaniummetalfromreactiveoxidesandnitrideswasnotavailable.1.4Non-ferrousAlloysOnceformed,titanium’sreactivityworkstoitsadvantage.Athin,tenaciousoxidecoatingformsonitssurface,givingexcellentresistancetocorrosion.This“passivation”willbediscussedindetaillater.Titaniumalloys,likeAlorMg,areoflowerdensitythaniron.1.4Non-ferrousAlloysAlthoughmoredensethanAlorMg,titaniumalloyshaveadistinctadvantageofretainingstrengthatmoderateservicetemperatures,leadingtonumerousaerospacedesignapplications.1.4Non-ferrousAlloysTitaniumsharesthehcpstructurewithmagnesiumleadingtocharacteristicallylowductility.However,ahightemperaturebccstructurecanbestabilizedatroomtemperaturebycertainalloyadditionssuchasvanadium.1.4Non-ferrousAlloysCopperalloyspossessanumberofsuperiorproperties.Theirexcellentelectricalconductivitymakescopperalloystheleadingmaterialforelectricalwiring.Theirexcellentthermalconductivityleadstoapplicationsforradiatorsandheatexchangers.1.4Non-ferrousAlloysSuperiorcorrosionresistanceisexhibitedinmarineandothercorrosiveenvironments.Thefccstructurecontributestotheirgenerallyhighductilityandformability.Theircolorationisfrequentlyusedforarchitecturalappearance.1.4Non-ferrousAlloysWidespreadusesofcopperalloythroughhistoryhasledtoasomewhatconfusingcollectionofdescriptiveterms.Themechanicalpropertiesofthesealloysrivalthesteelsintheirvariability.1.4Non-ferrousAlloysHighpuritycopperisanexceptionallysoftmaterial.Theadditionof2wberylliumfollowedbyaheattreatmenttoproduceCuBeprecipitatesissufficienttopushthetensilestrengthbeyond1000MPa.1.4Non-ferrousAlloysNickelalloyshavemuchincommonwithcopperalloys.WehavealreadyusedtheCu-Nisystemastheclassicexampleofcompletesolidsolubility.MonelisthenamegiventocommercialalloyswithNi-Curatiosofroughly2:1byweight.1.4Non-ferrousAlloysThesearegoodexamplesofsolutionhardening.Nickelisharderthancopper,butMonelisharderthannickel.Nickelexhibitsexcellentcorrosionresistanceandhightemperaturestrength.1.4Non-ferrousAlloysZincalloysareideallysuitedfordiecastingduetotheirlowmeltingpointandlackofcorrosivereactionwithsteelcruciblesanddies.Automobilepartsandhardwarearetypicalstructuralapplications.Zinccoatingonferrousalloysreimportantmeansofcorrosionprotection.Thismethodistermedasgalvanization.1.4Non-ferrousAlloysLeadalloysaredurableandversatilematerials.TheleadpipesinstalledbytheRomansatthepublicbathsinBath,England,nearly2000yearsagoarestillinuse.Lead’shighdensityanddeformabilitycombinedwithalowmeltingpointaddstoitsversatility.1.4Non-ferrousAlloysLeadalloysfinduseinbatterygrids(alloyedwithcalciumorantimony),solders(alloyedwithtin),radiationshielding,andsoundcontrolstructures.Thetoxicityofleadrestrictsdesignapplicationsandthehandlingofitsalloys.1.4Non-ferrousAlloysTherefractorymetalsincludemolybdenum,niobium,tantalum,andtungsten.Theyare,evenmorethanthesuperalloys,especiallyresistanttohightemperatures.However,theirgeneralreactivitywithoxygenrequiresthehightemperatureservicetobeinacontrolledatmosphereorwithprotectivecoatings.1.4Non-ferrousAlloysThepreciousmetalsincludegold,iridium,osmium,palladium,platinum,rhodium,ruthenium,andsilver.Excellentcorrosionresistancecombinedwithvariousinherentpropertiesjustifythemanycostlyapplicationsofthesemetalsandalloys.1.4Non-ferrousAlloysGoldcircuitryintheelectronicsindustry,variousdentalalloys,andplatinumcoatingsforcatalyticconvertersareafewofthebetterknownexamples.questionsTherearealotofalloysinwhichthereisnoiron.(T/F)Tungstencanbearthetemperatureof2000℃inair.(T/F)Listtheapplicationsthatthecopperalloymayhave.1.5CompositesOnecategoryofstructuralengineeringmaterialsisthatofcomposites.Thesematerialsinvolvesomecombinationoftwoormorecomponentsfromthe“fundamental”materialtypes.1.5CompositesAkeyphilosophyinselectingcompositematerialsisthattheyprovidethe“bestofbothworlds,”thatis,attractivepropertiesfromeachcomponent.Aclassicexampleisfiberglass.1.5CompositesThestrengthofsmalldiameterglassfibersiscombinedwiththeductilityofthepolymericmatrix.Thecombinationofthesetwocomponentsprovidesaproductsuperiortoeithercomponentalone.1.5CompositesManycomposites,suchasfiberglass,involvecombinationsthatcrossovertheboundariesofdifferentkindsofmaterials.Others,suchasconcrete,involvedifferentcomponentfromwithinasinglematerialtype.1.5CompositesIngeneral,weshalluseafairlynarrowdefinitionofcomposites.Weshallconsideronlythosematerialsthatcombinedifferentcomponentsonthemicroscopic(ratherthanmacroscopic)scale.1.5CompositesWeshallnotincludemultiphasealloysandceramics,whicharetheresultofroutineprocessing.Similarly,themicrocircuitsbediscussedlate