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1、Trans.NonferrousMet.Soc.China23(2013)1563−1569EnhancedgrainrefinementofcastaluminumalloybythermalandmechanicaltreatmentofAl−5Ti−BmasteralloyH.GHADIMI,S.HOSSEINNEDJHAD,B.EGHBALIFacultyofMaterialsEngineering,SahandUniversityofTechnology,51335-1996,Tabriz,IranReceived
2、2July2012;accepted13November2012Abstract:Al3TiandTiB2particleswithvarioussizesinAl−5Ti−B(massfraction,%)masteralloywereproducedbyliquid-phaseisothermalannealingandplasticdeformation.Theresultsshowthatwithdecreasingthesizeofparticlesinthemasteralloy,thegrainrefining
3、performanceisimprovedbut,therefinementoftheparticlesisuseful,andimmoderaterefiningprobablyacceleratesfadingofparticles,agglomeration,hencedecreasingthegrainrefinefficiency.Keywords:Al−5Ti−Balloy;grainrefinement;casting;inoculation;nucleationConsequently,itisassumed
4、thatAl3TiandTiB2particles1IntroductionpresentintheAl−5Ti−Bmasteralloyprovideheterogeneousnucleationsitesforthesolidgrain[1−3,7,Itiswellknownthatanequiaxedgrainstructure8,15,17].However,thesizeandmorphologyofthosemanifestsmoreenhancedmechanicalisotropythantheparticl
5、esshouldbeeffectiveinthegrainrefinement.columnarcounterpartinsolidificationstructureofcastFollowingthefact,recentinvestigationshaveindicatedmetals.Inaddition,fineequiaxedgrainstructuresexhibitthatthefragmentationofAl3Tiparticlesbymeansofimprovedcastingpropertiessuc
6、hassurfacequality,plasticdeformationsuchasrollingandextrusionimprovedfeedingtoeliminatetheshrinkageporosities,improvesthegrainrefiningefficiencyofAl−5Tianddecreasedhottearing,andreducedmoldfillingtime.ForAl−5Ti−Bmasteralloys[14,18].alongtime,grainrefiningofcaststru
7、ctureshasbeenTheaimofthepresentpaperistostudythepracticallyemployedbyaddinginoculantstothemeltinpossibilityofenhancedgrainrefinementofanaluminumfoundryprocesses[1−5].castmetalbymakingtheuseoffragmentedAl3TiandOneofthemostimportantgrainrefinersinTiB2particlesinanAl−
8、5Ti−Bmasteralloy.VarioussizesaluminumcastingistheAl−Ti−Bmasteralloy,holdingofparticleswereprovidedbyheattreatmentsandplasticTi/Bratios(moleratio)
