EFFECTOFPARTICULATESIZEANDCONTENTONSTRENGTHO FSiC_p/2024AlCOMPOSITEANDITSRELATIONSHIPWIT HT6-TREATMENT¥Ma,Zongyi;Liang,Yanan;Lu,Yuxi ong;Bi,Jing(InstituteofMetalResearch,Chines eAcademyofSciences,Shenyang110015)Abstract: Tensiletestsandfracturesurfaceobservationso ntheSiCp/2024Alcompositesfabricatedbypowder metallurgytechniguewerecarriedout.Itisindic atedthattheSiCparticulatesizeandcontenthave asmalleffectonthestrengthoftheas-extrudedco mposites.AftertheT6-treatment,theeffectincr easesobviously,andthestrengthofthecomposite sincreasesobviouslywithdecreasingSiCparticu latesizeandincreasingSiCparticulatecontent. T6-treatmenthasnoobviouseffectonthefracture surfaceofsmallparticulatecomposites.Forthel argeparticulatecomposites,thefracturedSiCpa rticulatesonthefracturesurfacesincreaseafte rT6-treatment.Theexperimentalresultswereacc ountedforbythemicrostructuralcharacteristic sandstrengtheningmechanismofthecomposites.K eywords:composite,particulate,aluminum,T6-t reatment,strength1INTRODUCTIONSiliconcarbid eparticulatesareutilizedtoproducecomposites withhigherstrengthandelasticmoduluscompared totheunreinforcedmatrixalloy.Thecompositesa rebeingincreasinglyconsideredforstructurala pplicationsintheaerospaceandautomotiveindus try.Generally,themodulus,fracturetoughness, strengthandductilityofthecompositesaredeter minedbytheparticulatesizeandthevolumefracti on,thematrixflowstressandtheinterfacebondin gbetweenparticulateandmatrixF[1-3].Itwasind icatedthatthestrengthofthecompositesincreas eswithincreasingparticulatevolumefractionan dwithdecreasingparticulatesize[4].Itwasrepo rtedthattheparticulatesinthecompositecracke dtypicallyforthosesizeabove15-20μm[3,5].The presentworkaimstoinvestigatetheeffectoftheS iCparticulatesizeandthevolumefractiononthes trengthandfracturebehavioroftheextrudedandT 6-treatedSiCp/2024Alcompositestounderstandt herelationshipbetweenpropertyandmicrostruct ure.2EXPERIMENTALPROCEDUREAtomized2024Alcon sistedof(%):4.20Cu,1.47Mg,0.56Mn,0.02Zr,0.4 0Si,0.27Fe)powderwithameansizeof60μmwasempl oyedasthematrix.α-SiCparticulatewithmeansiz eof3.5,10and20μmwereusedasthereinforcements .Thecompositescontaining15,20and30%(volumef raction)SiCparticulateswerefabricatedbyaP/M techniquewhichinvolvedmixingSiCparticulatew ithaluminumalloypowder,hotcompactioninvacuu m,andthenhotextrusionat450℃atanextrusionrat ioof20:1.Thespecimensfortensionandhardnesst estsweremachinedfromextrudedrods.Ahalfofthe specimenswasT6-treated(500℃/1hsolutionized, waterquenched,and170℃/5haged).Allthetensile specimensweretestedatastrainrateof8.33×10-4 s-1.Thetensilefracturesurfaceswereexaminedo nascanning①ReceivedJul.6,1994electronmicros cope(SEM).TheRockwellhardness(HRB)ofthepoli shedspecimenswasmeasured.Datawereobtainedfo reachspecimenbyaveragingfivemeasurements.3R ESULTSANDDISCUSSIONFig.1showsthedependenceo ftensilestrengthofthecompositesontheSiCpart iculatesize.Thestrengthoftheextrudedcomposi tesdecreasesveryslowlywithincreasingSiCpart iculatesize,indicatingthattheparticulatesiz ehasamarginaleffectonthestrengthoftheextrud edcomposites.AftertheT6treatment,thestrengt hofthecompositesissignificantlyimprovedduet otheprecipitationstrengthening,andincreases by100-150MPacomparedtotheextrudedcomposites .ItcanbenotedthattheeffectoftheSiCparticula tesizeonthestrengthofthecompositesincreases obviouslyaftertheT6-treatment,andthestrengt hoftheT6-treatedcompositesissubstantiallyra isedwithdecreasingtheSiCparticulatesize.The dependenceoftensilestrengthoftheextrudedand T6-treatedcompositesonSiCparticulatevolumef ractionisshowninFig.2.WithincreasingSiCpart icustrengthofbothextrudedandT6-treatedcompo sitesincreasesslowlyintheapproximatelysamew ay.WithincreasingSiCparticulatevolumefracti onfrom15%~30%,thestrengthoftheextrudedcompo sitesincreasesslowly,whereasthestrengthofth eT6-treatedcompositesincreasesobviously.For theceramicparticulatereinforcedaluminummatr ixcomposites,thestrengtheningmechanismismai nlyattributedtotheparticulate-dislocationinteractionbymeansoftheOrowanbowingmechanism[6],atthesametimetheparticulateload-bearingbymeansofinterfacialshearingalsocontributest
More abstracts about the EFFECT OF PARTICULATE SIZE AND CONTENT ON STRENGTH OF SiC_p/2024Al COMPOSITE AND ITS RELATIONSHIP WI