Metal-matrix-composites

CompositesDefineacompositematerial,themajorconstituent,andvariousclassifications.Describetheroleoftheparticulate(fiber)andthematrix(resin).Namevariousformsofeach.Describehowonewouldestimatethematerialpropertiesofafiberreinforcedcompositemateialsbasedonmaterialpropertiesandvolumefractionofthematrixandfiberconstituents.ⅠLearningobjectivesWhatisacompositematerial?Unfortunatelythereisnowidelyaccepteddefinitionofwhatacompositematerialis.Adictionarydefinesacompositeassomethingmadeupofdistinctparts(orconstiutents).attheatomiclevelmaterialssuchascomemetalalloysandpolymericmaterialscouldbecalledcompositematerialssincetheyconsistofdifferentanddistinctatomicgroupings.ⅡIntroductionAtthemicrostructurallevel(about10-4to10-2cm)ametalalloysuchasplain-carbonsteelcontainingferriteandpearlitecouldbecalledacompositematerialsincetheferriteandpearlitearedistinctlyvisibleconstituentsasobservedintheopticalmicroscope.Atthemacrostructurallevel(about10-2cmorgreater)aglass-fiber–reinforcedplastic,inwhichtheglassfiberscanbedistinctlyrecongnizedbythenakedeye,couldbeconsideredacompositematerial.ⅡIntroductionNowweseethatthedifficultyindefiningacompositematerialisthesizelimitationsweimposeontheconstituentsthatmakeupthemateiral.Inengineeringdesignacompositematerialusuallyreferstomaterialconsistingofconstituertsinthemicro-tomacroscalerange,andevenfavorsthemacros.ⅡIntroductionAcompositematerialismaterialssystemcomposedofsuitablyarrangedmixtureorcombinationoftwoormoremicro-ormacroconstituentswithaninterfaceseparatingthemthatdifferinformandchemicalcompositionandareessentiallyinsolubleineachother.ⅢDefinitionTheengineeringimportanceofacompositematerialisthattwoormoredistinctlydifferentmaterialscombinetoformacompositematerialthatpossessespropertiesthataresuperior,orimportantinsomeothermanner,tothepropertiesoftheindividualcomponents.ⅢDefinitionUnit10Metal-matrixcompositesMMCReinforcingconstituentpowdermetallurgyDiffusionbondingliquidphasesinteringSqueeze-infiltrationstir-castingCarbideoxidenitridenitrogenoxygenSpecificelasticmodulusThermalexpansivitythermalconductivityⅠNewwordsTransversestrengthchemicalinertnessPRMselectronicpackagingIsotropicanisotropicMonofilament-reinforcedmetalsInterpenetratingphasecompositespercolatingphaseLiquidphasesinteredmetallicmaterialsInternalstressinterfacialbondstrengthⅠNewwords10.1IntroductionAmetal-matrixcomposite(MMC)combinesintoasinglematerialametallicbasewithareinforcingconstituent,whichisusuallynon-metallicandiscommonlyaceramic.Bydefinition,MMCsareproducedbymeansofprocessesotherthanconventionalmetalalloying.Liketheirpolymer-matrixcounterparts,thesecompositesareproducedbycombiningtwopre-existingconstituents,(e.g.ametalandaceramicfibre).Processescommonlyusedincludepowdermetallurgy,diffusionbonding,liquidphasesintering,squeeze-infiltrationandstir-casting,alternatively,thetypicallyhighreactivityofmetalsatprocessingtemperaturescanbeexploitedtoformthereinforcementand/orthematrixinsitu,i.e.bychemicalreactionwithinaprecursorofthecomposite.10.1IntroductionThereareseveralreasonswhyMMCshavegeneratedconsiderableinterestwithinthematerialscommunityfornearly30years.(1)The“composite”approachtometallurgicalprocessingistheonlypathwayfortheproductionofentireclassesofmetallicmaterials.Onlyinthiswaycanaluminium,copper,ormagnesiumbecombinedwithsignificantvolumefractionsofcarbide,oxideornitridephasesbecause,unlikeiron,thesolubilityofcarbon,nitrogenoroxygeninthemoltenmetalis(withtheexceptionofOinCu)fartoolow.10.1Introduction(2)theapproachfacilitatessignificantalterationsinthephysicalpropertiesofmetallicmaterials.Compositesofferscopeforexceedingthespecificelasticmodulusvalueofabout26J·kg-1,whichisexhibitedbyallthemainengineeringmetals.Compositesalsooffertheonlypath-wayforproducingmaterialswithtailoredphysicalpropertycombinations:anexampleisthatoflowthermalexpansivitycombinedwithhighthermalconductivity,acombinationofimportanceforelectronicpackaging.10.1Introduction(3)MMCsoffersignificantimprovementsovertheirpolymermatrixcounterpartswithregardtoseveralproperties,includingtoleranceofhightemperature,transversestrength,chemicalinertness,hardnessandwearresistance,whilesignificantlyoutperformingceramicmatrixcompositesintermsoftoughnessandductility.10.1Introduction(4)Exceptionalpropertiescanbeobtainedinsomecases.Anexampleisthatof3M'sNextel-reinforcedaluminiumcomposites,whichexhibitalongthefibredirectionatensilestrengthof1.5GPa，acompressivestrengthof3Gpaandatransversestrengthabove200MPa,inmaterialofdensityonlyslightlyabove3g·cm-3.10.1IntroductionMMCscomeinseveraldistinctclasses,generallydefinedwithreferencetotheshapeoftheirreinforcement.Particle-reinforcedmetals(PRMs)containapproximatelyequiaxedreinforcements,withanaspectlessthanabout5.Thesearegenerallyceramic(SiC,AL2O3,etc.).PRMscommonlycontainbelow25vol.%ceramicreinforcementwhenusedforstructuralapplications,butcanhaveasmuchas80vol.%ceramicwhenused10.1Introductionforelectronicpackaging.Ingeneral,PRMsareatleastapproximatelyisotropic.Theyareproducedusingbothsolids