ImprovementofSiC_pReinforcedCastAluminiumCom positesbytheROCMethodZhengQifei,XieShuishen g,YuanGuansen,ShiLikai(郑弃非)(谢水生)(袁冠森)(石力开)J in.Qijian,NiuHuiling(金其坚)(牛慧铃)(GeneralResea rchInstituteforNon-ferrousMetals,'Beijing10 0088,China)Received4January1996Improvemento fSiC_pReinforcedCastAluminiumCompositesbyth eROCMethod¥ZhengQifei;XieShuisheng;YuanGuan sen;ShiLikai(郑弃非)(谢水生)(袁冠森)(石力开)Jin.Qijian; NiuHuiling(金其坚)(牛慧铃)(GeneralResearchInstitu teforNon-ferrousMetals,'Beijing100088,China )Received4January1996AbstractTheprocessofra pidomnidirectionalcompaction(ROC)ofSiC_p/ca stAlcompositieswasinvestigated.Anapparatusf orROCprocesswasestablished.Fullcompactibili tyofvariousSiC_p/castAlcompositeswasaccompl ished.TheeffectsinthematerialsWereeliminate d.ItisfoundthatafterROC,thetensilestrengtho fthe30%SiC_p/Z1109compositeincreasedby35%.I tisdemonstratedthattheROCprocessisaneffecti vemethodforimprovingtheperfermanceofSiC_p/A lcompletes.KeyWords:RapidOmnidirectionalCom paction,SiC_p/Alcomposite,ROC1.Introduction SiC_p/Alcompositeisanattractivema-terialfor bothstructureandnon-structureapplicationbec auseoftheiruniquecombina-tionofhighstrength -to-weightratio,highstiffness-to-weightrati o,excellentwearre-sistanceandgoodthermostab ility.Formostmanufactureofthematerial,casti soneofthecompetitiveprocesses,becauseofthel owcost.Generally,therearemanyde-fectssuchas porosityinthecastmaterial,whichaffectstheir propertiesandapplica-tions.Soitisnecessaryt ousesubsequentformingorthehigh-costHIP(hot- isosta-tic-pressing)processtoimprovepropert iesofcastmaterials.ROCprocessisapseudo-HIPt ech-nique.Inthecaseofachievingthesameeffect ofHIP,usingROCprocesscanlow-ertheproduction costandobtainexcellentmicrostructuresandpro pertiesofthemateri-al,becauseofthecombinati onofhighpre-ssure,shorttimeandlowtemperatur eoftheprocess ̄[1,3].Previousworkhasshowedth atceramic/metalcompositesareaparticu-larlys uitableclassofmaterialsforROCpro-cessing[3] .TheobjectiveofthisworkwastostudytheROCproc essofSiC_p/castAlcom-posite.2.ExperimentalP rocedureTheROCprocessesarecarriedoutinadevi ceinstalledinaconventional2MNoilpress.Inthe methodathick-walledcontai-nercalleda“fluidd ie”(Fig.1)wasusedwhichismadeofmaterialscapa bletoplas-ticflowatcompactiontemperatureand pre-ssure.Theas-processedmaterialwascon-tai nedinthefluiddie.Thefluiddieactsasanincompr essiblefluid.Whenanexternalpressurewasappli ed,ittransmitssuchpre-ssuretoallsurfacesoft heas-processedma-terial.Thepressurewasappli edbyinsert-ingthepreheatedfluiddieassemblyi ntoapotdieofthedeviceandrammingthen.Inthisw ork,apreheattimeof30minandapressuredwelltim eof15swereused.Thehighestpressureandtempera turewhichmaybeusedinthisprocessare1000MPaan d1300℃.Thematerialsusedinthisprogramwereeas tZ1109alloysreinforcedbySiCparticles.Thecon tentsoftheSiCwere20%~30%andthesizeofSiCpart icleswasabout50μm.Densitytestsandmetallo-gr aphicalexaminationsweremadeforbothas-castan dROCmaterials.Toinvestigatethestrengthvaria tion,4samples(No.1,2,3,4)werecutfromone30%S iC_p/Z1109ingot.Two(No.3,43ofthemwereROCtre ated.AfterT6treatment(530℃/2h/WQ,agingat225 ℃/8h),roomtemperaturetensiletestswereconduc tedinaInstrontensiletestma-chine.3.Resultsa ndDiscussionAsetofpressure-densitycurvesare showninFig.2forcompactionof30%SiC_p/Z1109co mpoite.Thesecurvesindi-catethatincreaseofte mperatureresultsinincreasingdensityforacons tantpressure.Ontheotherhand,foraconstanttem pera-turethedensityincreasesalongwiththein- creasingofpressure.Obviously,manycombinatio nsofpressureandtemperaturethatwouldresultin fulldensitycanbeused.Thedensitiesoftheas-or ocessedmate-rialsbeforeandafterROCprocessat tem-peratureof500℃andpressureof500MPaarelis tedinTable1.Itcanbefoundthatfortheas-proces sedmaterialsthefulldensi-tycanbeachievedatt hetemperatureof500℃andthepressureof500MPa.T hemicrostructuresof30%SiC_p/Z1109before(Fig .3a)andafter(Fig.3b)ROCprocessareshowninFig .3.Itcanbeseenthattherewereobviousholesinth eas-castmaterialandthataftertheROCprocessthoseholeswereeliminated.Moreover,itcanalsobefoundthataftertheROCprocessthelargerSiCparticleshavenotbeenbroken.Thisisofimportanceto
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