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外文翻译--复合材料mg2si-al的冷却斜槽法铸造和其局部重熔演化过程中的半固态微观结构 英文版.pdf

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外文翻译--复合材料mg2si-al的冷却斜槽法铸造和其局部重熔演化过程中的半固态微观结构 英文版.pdf

MaterialsScienceandEngineeringA444200799–103SemisolidmicrostructureofMg2Si/AlcompositebycoolingslopecastanditsevolutionduringQ.D.Qin,Y.G.Zhao∗,P.J.Street,acceptedAbstractfabricatedmicrostructure,,sizethatareshape©K1.lotminimizingandsemisolidoftureneededisconstitutedofsolidphaseglobulessuspendedintheliquidphase.Thethixotropiceffectofthesemisolidalloysallowsthemtobehandledasamassivesolidandtoattainfluidlikepropertieswhenshearedduringshaping2.ManydifferentroutessuchstraintialRecentlysemisolidKleinerallogrofloofprocessallosphericalSuzukithixoforminginofpotentialasautomobilebrakediscmaterialbecausetheintermetalliccompoundofMg2Siexhibitshashighmeltingtemperature,lowdensity,highhardness,lowthermalexpansioncoefficientandreasonablyhighelasticmodulus8.However,09215093/doihavebeenusedtoproducenondendriticmicrostructure,asmagnetohydrodynamicMHDstirring,sprayforming,inducedmeltactivatedSIMA/recrystallisationandparmeltingRAP,liquidus/nearliquiduscastingetc.3–8.,Czerwinski9–11investigatedthefabricationofMgalloyscomponentsbyinjectionmoldingprocess.etal.12studiedtheformationofsemisolidMg–Al–Znybyextrudedmethod.Wuetal.13constructedamodelonwthmorphologyofsemisolidmetals,usingsolidificationandwspeedoftheliquidasvariationsaffectingthemorphologycrystals.AmongallthetechniquesofSSP,thecoolingslope∗Correspondingauthor.Tel.864315094481fax864315095592.Emailaddresszhaoygjlu.edu.cnY.G.Zhao.thecoarsereinforcementoftheprimaryMg2Siparticlesinthenormalcompositeleadstopoorproperties.Therefore,thecompositewithcoarseprimaryMg2Siparticlesneedtobemodifiedtoobtainadequatemechanicalstrengthandductility.IthasbeenreportedthatrareearthelementssuchasCe16,Sr17anditssalts18,19havethepowertomodifythemorphologyofprimaryMg2Si.Asemisolidmicrostructureinthecompositeisexpectedtoimprovethemechanicalproperties.ThesemisolidofMg2Si/AlcompositehasbeenproducedviaSIMAinpreviousstudy8.However,thistechnologyisrelativecomplexbecauseofrequiringcoldextrusionanddeformation.LessworkhasbeencarriedoutonsemisolidMg2Si/Alcompositebythecoolingslopecastandpartialremeltingprocess.Inthepresentstudy,asemisolidofinsituMg2Si/Al–Si–Cucompositewaspreparedbythecoolingslopecastandpartialremeltingprocess,–seefrontmatter©2006ElsevierB.V.Allrightsreserved.10.1016/j.msea.2006.08.074KeyLaboratoryofAutomobileMaterialsofMinistryofEducationJilinUniversity,No.142RenminReceived17April2006AninsituMg2Si/Al–Si–CucompositewithsemisolidstructurewasandeffectofisothermalholdingtimeonthemorphologythemorphologyofprimaryMg2SiandH9251AlgrainsinthecompositefactorofH9251Algrainsincreasewiththeisothermalholdingtime.2006ElsevierB.V.Allrightsreserved.eywordsSemisolidAluminumCompositesMicrostructureMagnesiumsilicideIntroductionIthasbeenwellknownthatsemisolidprocessingSSPhasaofsignificantadvantagesoverconventionalcasting,suchasthemacrosegregationandsolidificationshrinkagereducingtheformingtemperature.Thekeythatpermitsthealloystoshapeistheabsenceofdendriticmorphologythesolidphase1.ThetypicalnondendriticmicrostrucpartialremeltingprocessCong,W.Zhou,B.XuandDepartmentofMaterialsScienceEngineering,Changchun130025,PRChina15August2006bycoolingslopecastandpartialremeltingprocess.Theascastandshapefactorofthegrainswereinvestigated.Theresultsshowglobularand/orellipticafterpartialremeltingprocess.Thesizeandisasimpleroute.Theprimaryphaseinthesemisolidybythecoolingslopecasthasbeenreportedtobecomeafterremeltedinthesemisolidstate14.Hagaand14,15investigatedtheproducingprocessofingotsforofAl–6Sialloysbycoolingslopecasting.HypereutecticAl–SialloyswithhighMgcontentisinfactansitualuminummatrixcompositescontainingalargeamounthardparticlesofMg2Si,andtheMg2Si/Alcompositehasa100Q.D.Qinetal./MaterialsScienceandEngineeringA444200799–103Table1ChemicalcompositionsoftheMg2Si/Alcompositewt.MaterialsAlMgSiCuCrZnNiFeAl–Si–Mg–CuBal.13.27611.2813.52399.7purityandmagnesiumingot,98.0purityusedtopreparetheexperimentalalloy.About520gofmasteralloymeltwasmolteninagraphitecrucibleinanresistancefurnace.About100gofmagnesiumand26gCu,preheatedat300◦C,wereaddedintotheAl–Simeltat◦C.Afterholding15min,themeltwerepouredintoamoldviaaaluminumcoolingslopepreheatedat300◦CtotheinsituMg2Si/Alcompositeingots,andthechemcompositionsarelistedinTable1.TheschematicoftheprocessisshowninFig.1adoptedfrom15.Sub,theingotwascutintoaseriesofcubicsamplesofmm12mm12mm.Thepartialremeltingprocesswasinaverticaltubefurnace,andthesampleswereheatedto560◦Candheldatthetemperaturefor30,60,180andmin,respectively,andthenwerequenchedincoldwater.Metallographicspecimenswerepolishedthroughstandardandthemicrostructureinthemexaminedusinganmicroscopy.A0.5hydrofluoricacidHFaqueouswasusedastheetchantofpolishingsamples.ThegrainFig.2.AscastmicrostructuresofMg2Si/Alcompositesbyathenormal200H9262m,andtheH9251Alwasdendriticaswell.However,afterthesolidwiththecoolingslope,themorphologyofH9251Alinthecompositebythecoolingslopcastchangesfromtospheralwithadiameterof∼10H9262m,andtheprimary2Sicrystalsbecomefineobviously,asseeninFig.2b.Oneforitisduetotheincreaseinthenucleationsubstratesthemeltaftercastingwiththecoolingslopeanotherreasonrelatedtotheflowofthemeltontheslope.Theflowingmeltcausepartialfragmentsofthedendritesofthedendritesbyvection.Fig.3a–dshowstheevolutionofthesemisolidmicrostrucofthecompositebythecoolingslopecastwiththetimeofisothermalheattreatmentof30,60,180andmin,respectively.Fig.3ashowsthattheascastcoarse2Sidendritesarefragmented,changingtoanirregularwithslightlyroundedtips,andthemorphologyofH9251Alvebecomesglobularwithameansizeof∼51H9262m.Asthetimeincreasesto60min,themorphologyoftheMg2SiinthecompositebecomesmainlyellipticshapeandtheofH9251Albecomesmoreglobularwithameansize∼85H9262mseeninFig.3b.Furthermore,italsoshowsthatsomeH9251AlgrainsisnotdissolvedcompletelysurvivingintheasindicatedbywhitearrowsinFig.3b.Fig.3cshowsthecastadoptedfrom8andbthecoolingslopecast.Q.D.Qinetal./MaterialsScienceandEngineeringA444200799–103101Fig.castandmicrostructure180notincreasesgrainsH9251surviofasinparticles.liquidduringfurthergrainsshapetreatmenttheasobofsmallerThesolidificationquenchingmay3.SemisolidmicrostructuresoftheMg2Si/Alcompositebythecoolingsloped600min.ofthecompositewithaisothermaltreatmentformin.ThemorphologiesoftheMg2SiandH9251Alparticlesdochangeobviously,however,themeansizeofH9251Alparticlesto∼111H9262m.ItisofinteresttonotethatsomesmalleremergeonthesurfaceofthelargeglobulargrainsofAl,asindicatedbyblackarrowsinFig.3c.Theamountofthevedsmallsolidparticlesincreases,incomparisonwiththat60minholdingtime.Itseemsthattheliquidfractionincreaseswell.Unfortunately,theliquidfractioncouldnotbemeasuredthepresentstudy,becauseofthesurvivedofthesmallsolidPoirieretal.20reportedthatthevolumefractionofofAl–Cualloyslightlydecreasedatthecoarseningperiodsemisolidisothermaltreatment.Thephenomenonneedsstudy.Fig.4ashowsthatthemorphologyofthesmalleriscolumnarandsomesurvivedsolidphasesareirregularasdenotedbythewhitearrowinFig.4a.AstheisothermalFromtheticlesofformationFig.4.Metallographsofthecompositeswiththeisothermaltimeofawithdifferentisothermalholdingtimeofa30min,b60min,c180mintimeincreasesupto600min,themorphologiesofprimaryMg2SiparticlesandH9251Algrainsarestillglobular,showninFig.3d.ThesizeoftheH9251Algrainsincreaseviouslywithameansizeof149H9262m.Inaddition,theamountthesurvivedsolidparticlesevidentlydecreases,andthegrainsonthesurfaceoflargeH9251Algrainsdisappear.smallergrainsemergencemaybetheconsequenceofoftheliquidduringhandlingofthesamplesbeforeinwater,andthatemergenceanddisappearancebeduetothedifferenceofthehandletimeforquenching.Fig.4b,itisclearlyindicatedthatthemorphologiesofsurvivedsolidparticlesdonotchangeobviously.Togetbetterunderstandingoftheevolutionofthesolidparisofimportant,becauseitdeterminesthefinalgrainsizethecomposite,andthusthemechanicalproperties21.Theofasemisolidstructurebyisothermalholdingfroma180minandb600min,showingtheH9251Alsmallergrains.102Q.D.Qinetal./MaterialsScienceandEngineeringA444200799–103Fig.con8iscastisothermalarmsellipsoidalandclesisjoiningcoarseningtheincanacterizedFwhererespectiisothermalshapetimetimethatthataslosolidvtheofInmicrostructuresofhardFig.ingdissolvcessthe4.successfullyremeltingofobincreasemeanmorphologyH9251timeAcknoneeringFRefer5.TherelationshipofthemeansizeofH9251Algrainsandtheholdingtime.ventionallycastdendriticstructurehasbeenstudiedearlier.Thetransitionofthesolidphasefromdendriticintospheralthoughttobeduetotheliquidpenetration,namely,theasgrainboundaryispenetratedbyliquidduringthesemisolidholding,causingthefragmentationofthedendriteandthen,thefragmentedarmschangeintospheroidalorgrains.TherelationshipbetweenthegrainsizeoftheH9251AlparticlesholdingtimeisshowninFig.5.ThesizeoftheH9251Alpartiincreaseswiththeholdingtime.Onecoarseningmechanismthecoalescenceofthegrains,namely,twograinsencountertogetherandformingnewbiggergrain22.AnothermechanismistheOstwaldripening22,23,inwhichlargergrainsgrowandthesmallergrainsremelt.Usingtheimageanalysissystem,thenumberoftheobjectsaselectedarea,andtheperimeterandareaofselectedobjectsbemeasured2.Normally,theshapeofanobjectischarbytheshapefactorF0definedas204πA0P201A0andP0representtheareaandperimeteroftheobject,vely2.ThechangeoftheshapefactorduringthetreatmentisshowninFig.6.Itisindicatedthatthefactorincreasesrapidlyfrom0.51to0.69withtheholdingfrom30to180minandhowever,amuchlargerholdingcannotresultinaconsiderablechangeofF0,suggestingtheF0seemstoreachtoamaximumvalue.Itisreportedthesolidphaseparticlestendtobecomespherical,but,forlongerholdingtime,thechangeoftheshapeoftheparticleswsdownandevenreversesinthecaseofthehighvaluesofvolumefraction21.Keepinginmindthatthehighsolidolumefractionmeansalsoahighcontiguity,thisreversionfromsphericalshapecanbeattributedtothehardimpingementthesolidparticles,leadingtothelocalshapedistortions21.thepresentstudy,however,thesolidvolumefractionintheislowerrelatively≤0.6accordingtotheresultthequantitativeanalysis,andconsequently,thechanceoftheimpingementisloweraswell.Withincreaseinthehold106.RelationshipoftheshaperfactoroftheH9251Algrainsanttheholdingtime.time,thehighercurvaturepartofthesolidparticlewillbeed,andleadingtotheincreaseoftheF0.Finally,theproreachestoadynamicequilibriumandtheshapefactorofgrainswillnotchange.ConclusionThesemisolidstructureofinsituMg2Si/Alcompositeisproducedbythecoolingslopecastandpartialprocess.TheresultsshowthatathemorphologyprimaryMg2Siphaseisglobularand/orellipticnotchangingviouslywithincreaseintheisothermalholdingtimebwithintheisothermalholdingtimefrom30to600min,thesizeofH9251Algrainsincreasesfrom50to150H9262m,anditsbecomesmoreglobularctheshapefactoroftheAlsolidparticlesrapidlyfrom0.51to0.69withtheholdingfrom30to60min.wledgementsThisworkissupportedbyTheProject985AutomotiveEngiofJilinUniversityandTheInnovationandInventionoundationofJilinUniversity2003CX029.ences1E.Tzimas,A.Zavaliangos,Mater.Sci.Eng.A2892000217.2W.R.Loue,M.Suery,Mater.Sci.Eng.A20319951.3H.V.Atkinson,Prog.Mater.Sci.502005341.4M.P.Kenney,J.A.Courtois,R.D.Evans,G.M.Farrior,C.P.Kyonka,A.A.Koch,K.P.Young,MetalsHandbook,vol.15,19thed.,ASMInternational,MetalsPark,OH,USA,1988,p.327.5P.J.Ward,H.V.Atkinson,P.R.G.Anderson,L.G.Elias,B.Garcia,L.Kahlen,J.M.RodriguezIbade,ActaMater.4419961717.6K.P.Young,C.P.Kyonka,J.A.Courtois,Finegrainedmetalcomposition,USPatentno.4,414,37430March1982.7EuropeanPatent0745694A1,Methodandapparatusofshapingsemisolidmetals,UBEIndustriesLtd.1996.8Q.D.Qin,Y.G.Zhao,K.Xiu,W.Zhou,Y.H.Liang,Mater.Sci.Eng.A4072005196.9F.Czerwinski,ActaMater.5320051973.F.Czerwinski,Mater.Sci.Eng.A392200551.

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