贝氏体碳化物的形貌及形成机制

29120082TRANSACTIONSOFMATERIALSANDHEATTREATMENTVol.29No.1February2008刘宗昌,王海燕,王玉峰,任慧平,李文学(,014010):,:(BF)BFPC,H(Fe,M)3C;,,,,,,,:;;;:TG14:A:1009-6264(2008)01-0032-07MorphologyandformationmechanismofbainiticcarbideLIUZong-chang,WANGHa-iyan,WANGYu-feng,RENHu-iping,LIWen-xue(SchoolofMaterialandMetallurgy,InnerMongoliaUniversityofScienceandTechnology,Baotou014010,China)Abstract:Themorphologyofbainiticcarbides(CBF)invariousindustrialsteelswasexaminedbyscanningelectronmicroscopy(SEM)andtransmissionelectronmicroscopy(TEM).Theresultsshowthatthebainiticcarbidespresentindifferentshapesofshortbar,lamellaandwedgeinthesteels.Thecarbidecannotnucleatefrominsideofbainiticferritebecausetheferritecannotprovidetheconditionfornucleationofthecarbide.BainiticcarbidenucleatesatboundariesofBFPC,andgrowsupintothesub-unitsofbainiticferriteoraustenitealongtheboundaries.H(Fe,M)3Candferriteofupperbainitearrangesparallesly,andthewedge-shapedcarbidesinlowerbainitegrowupintothesub-unitsoftheferriteorcarbon-richaustenite,andtheelangatedcarbidesshowacertaindegreefromtheplate-lengtheningdirectionofferrite.Upperorlowerbainiticcarbidestopsthegrowthwhenitissurroundedbytheferrite.Thecarbonatomsmovebylong-rangediffusionandironatomsandsubstitutionalatomstransferbythermalactivationwayalongtheboundariesintheformationprocessofbainiticcarbides,thismadethecrystallatticerepacked.Keywords:bainite;carbide;diffusion;thermalactivation:2007-05-28;:2007-08-13:(NJ06073):(1940)),,,,190,E-mail:[e-mail](Bc),;,,,,,AC,APC[1,2],,,GCr15P209Cr2Mo71823MnNiCrMoT835CrMo,3mm,,QUANTA)400JEM)2010,)1贝氏体碳化物的形貌1.1H-(Fe,M)3C,,H,GCr151000e,450e,,,QUANTA-400,,121,,,2,(BF),,,,,,335Cr2Mo(P20)1SEMGCr15Fig.1SEMmicragraphshowingthemorphologyofupperbainiteinGCr15steel2SEMGCr15Fig.2SEMmicrographshowingthemorphologyofupperbainiteinGCr15steel3TEM35Cr2MoFig.3TEMimagesshowingthemorphologyofupperbainitein35Cr2Mosteel,(BF),,,H(Fe,M)3C,,,[1]1.2++,H,E,,55b~60b4P20,370e,,55b~60b,H,E,,EH[1,2]H9Cr2Mo1100e,350e,+,5331:4TEMP20(370e)Fig.4TEMimagesshowingthemorphologyoflowerbainiteinP20steel(isothermaltransformationat370e)5SEM9Cr2Mo+Fig.5SEMimagesshowingthemorphologyoflowerbainiteandmartensitein9Cr2Mosteel6SEMGCr15Fig.6SEMmicrographsshowingthemorphologyoflowerbainiteinGCr15steel,,6GCr151000e,300e,,6(a)10min,,,6(b)10min,,,,,,,,,,,,,2贝氏体碳化物的形核2.1H(Fe3C)E(Fe214C),,,,AC,APC,,,(BF),(C),3429BFPC,H,,,,,[2],Bc,),(0103wt%),,,[1,3]2.2E,727e010218%C(),A-Fe;,01001%C[4],C,7Fig.7Metastableequilibriumdiagramofsupercooledaustenite,,,,C,7,CT,A+F,,(BF)CBF,CC,,010218%C,(BF)500nm,,[5]Aaronson0103%()[5]4,2@1010cm-22@1012cm-2,012%C(),[6],,,,,,,,,,,012wt%A(BF)E[1,6]2.3(Bc)),,[7],8(a)P20,8(b)23MnNiCrMo,,BcH,,Bc,,8(b)(8b)8TEM,P20(a)23MnNiCrMo(b)Fig.8TEMimagesshowingthemorphologyoflowerbainiteinP20steel(a)and23MnNiCrMosteel(b)9GCr15950e,220e,,,,351:9SEMGCr15()Fig.9SEMmicrographsshowingthemorphologyoflowerbainiteinGCr15steel11Fig.11Schematicdiagramofformationofcarbidesinupperbainite,APC,[1]E-Fe214C719wt%,H-Fe3C617wt%,,,;E-Fe2.4C()H-Fe3C();,C,,,BFPC,,,,BFPC,BFPC,Bc,,:BFPC3贝氏体碳化物的长大,,,,,,10BFPC,,,H,121110SEM20CrMoFig.10SEMmicrographsshowingthebainiticferritelamellaeparallelgrowingfromgrainboundarytocrystalline12-12(a),,BF(12b),,362912-Fig.12Schematicdiagramofnucleationandgrowthoflowerbainiteferritesubumitsandbainiticcarbide,BFPCH(12c),BcPBFBcPC,,,,,,,(12d):BFPC,,,,,,,,,,,4贝氏体碳化物形核)长大时原子的位移方式H,,,H-Fe3C6167wt%,93133wt%,,Bc,Bc,Bc;,,):,,,,,600~700e(300~400e),C-FeD10-20~10-24cm2#s-1,6~9,,,,,[8]BF),,(Bc),,,,)BcPBFBcPC,,Bc,,5结论1)H-(Fe,M)3C;;2),,012wt%);3),(Bc)BFPC;(46)371:[1]StorojevaL,KasparR,PongeD.Effectsofheavywarmdeformationonmicrostructureandmechanicalpropertiesofamediumcarbonferritic-pearliticsteel[J].ISIJInternational,2004,44(7):1211-216.[2]StorojevaL,PongeD,KasparR,etal.DevelopmentofmicrostructureandtextureofmediumcarbonsSteelduringheavywarmdeformation[J].ActaMaterialia,2004,52:2209-2220.[3]XiongY,SunSH,LiY,etal.Effectofwarmcrosswedgerollingonmicrostructureandmechanicalpropertyofhighcarbonsteelrods[J].MaterialsScienceandEngineeringA,2006,431:152-157.[4],.[J].,1999(2):21-25.WEICheng-fu,WANGXue-qian.Unusualdecompositionofundercoolingausteniteandcarbidegranulation[J].HotWorkingTechnology,1999(2):21-25.[5],.[J].,2002(1):32-34.HEYi,WangXue-qian.Theresearchofthefastspheroidizingannealingtechniqueforhigh-carbonsteel[J].HotWorkingTechnology,2002(1):32-34.[6],.Ac1f[J].,2002,27(5):39.HeYi,WangXue-qian.SpheroidizingmechanismandAc1ftemperatureequalizationspheroidizingannealingtechnologyforhigh-carbonsteel[J].HeatTreatmentofMetals,2002,27(5):39.[7],.[J].,1999,17(1):48-52.WEICheng-fu,WANGXue-qian.Studyonthemechanismoftheausteniteofinhomogenouscarbonconcentrationinthespheroidizingannealing[J].MaterialsScienceandEngineering,1999,17(1):48-52.[8],.[J].,1996,17(2):17.WANGXue-qian,WANGYan-ping.Controlanduseofresidualausteniticmorphologyinhigh-carbonsteel[J].TransactionsofMetalHeatTreatment,1996,17(2):17.[9]MakiT.Formationof(A+H)microduplexstructureanditsmechanicalpropertiesinhighcarbonsteel[A].ProceedingsoftheSecondInternationalConference