简介:Inthispaper,themicrostructureandhardnessofHG980Dheat-affectedzone(HAZ)atdifferentcoolingratet8/3werestudied,theimplantcriticalfracturestressunderthreediffusiblehydrogenconditionsweremeasured,andthehydrogen-inducedcracking(HIC)fractographofsteelHG980Dwereanalyzed.TheexperimentalresultsshowthatmartensiteexistsinHAZofHG980Dtillt8/3≥150s,thehardenquenchingtendencyofHG980Disgreater;Theimplantcriticalfracturestressisrelatedtodiffusiblehydrogencontentsignificantly,atlowhydrogenlevel,highrestraintstressisneededtonucleateHIC,thefractographismainlymicrovoidcoalescence,butathighhydrogenlevel,onlysmallrestraintstresscancauseHICoccurrence,thefractographismainlyquasicleavage.Itisveryimportanttochooseultra-lowhydrogenweldingconsumabletoweldsteelHG980Dtopreventhydrogen-inducedcracking.
简介:Microstructuresandmechanicalpropertiesoftransientliquidphase(TLP)bondedmagnesiummetalmatrixcomposite(MMC)jointsusingcopperinterlayerhavebeeninvestigated.Withanincreaseofbondingtimesfrom5minto50minatbondingtemperatureof510℃,theaverageconcentrationofcopperinthebondedzonedecreased,themicrostructureinthezonechangedfromCu,α-MgandCuMg2toα-Mg,CuMg2andTiC,andmechanicalpropertiesofthejointincreased.Theshearstrengthofthejointbondedat510℃for50minreached64MPaduetothemetallurgicalbondingofthejointandimprovingitshomogeneityofcompositionandmicrostructure.ItisfavorabletoincreasethebondingtimeforimprovingmechanicalpropertiesofTLPbondedmagnesiumMMCjoint.
简介:Themechanicalproperties,creepdamage,creeprupturestrengthandfeaturesofinterfacialfailuresofweldedjointsbetweenmartensite(SA213T91)andpearlitesteel(12Cr1MoV)havebeeninvestigatedbymeansofargontungstenpulsedarcwelding,hightemperatureacceleratedsimulation,creeprupture,mechanicalpropertytestsandscanningelectronicmicroscope(SEM).Theresearchresultsindicatethatthemechanicalpropertiesofovermatchedandmediummatchedjointdeteriorateobviously,andtheyaresusceptibletocreepdamageandfailureafteracceleratedsimulationoperation500h,intheconditionofpreheat250℃,andpostweldingheattreatment750℃×1h.However,themechanicalpropertiesofundermatchedjointarethebest,theinterfacialfailuretendencyofundermatchedweldedjointislessthanthoseofmediumandovermatchedweldedjoint.Therefore,itisreasonablethatlowalloymaterialTR31isusedasthefillermetalofweldbetweenSA213T91and12Cr1MoVsteel.
简介:ThediffusionbondingofAZ3\BMgalloyandQ235steelwasinvestigatedwithaZn-5AIalloyasinterlayerandunderdifferentholdingtimerangingfrom3to1200s.Themicrostructureandphasecompositionsofbondedjointswerecharacterizedbyscanningelectronmicroscopy(SEM),energydispersivespectrometer(EDS)andX-raydiffraction(XRD)methods.TheshearstrengthofMgalloy/steeljointswasmeasuredbytensiletester.Itwasfoundthatthemicrostructureofbondedjointsevolveddramaticallyalongwiththeprolongationofholdingtime.Undertheholdingtimeof3s,themainpartofjointwascomposedofMgZn2phaseanddispersedAl-richsolidsolutionparticles.Whenincreasedtheholdingtimemorethan60s,theexcessivesolutionofAZ3\Bintotheinterfacialreactionarealedtotheformationofcoarsephaseandeutecticmicrostructure,andalsothecomplexFe-AlandMg-Al-ZnIMCsattransitionlayerclosedtoQ235steelside.Accordingtothetensiletestingcharacterizations,thejointsobtainedunderholdingtimeof3sexhibitedthebestshearstrengthof84MPa,andthefractureoccurredattheintermediarypartofjointwheretheflexibleAl-richsolidsolutionparticlescouldhelptoimpedethemicrocrackpropagations.Withprolongingtheholdingtimeto600s,theshearstrengthofjointswasdeterioratedenormouslyandthefracturepositionwasshiftedtothetransitionlayerpartclosedtoQ235steel.