简介：Themicrostructureandpropertiesofacombinedprecipitationhardeningultrahighstrengthsteelwithnano-sizedcarbidesandintermetallicswerestudiedsystematically.Theresultsshowthataftertemperingat300℃lotsofε-carbidesareprecipitatedinthemartensite,thestrengthrisesandthetoughnessfallsslightly.Aftertemperingat430℃,muchcoarsercementitelaminaareprecipitatedinmartensiticlaths,whichcausestheimpacttoughnessfallstotheminimumvalue.WithtemperaturefurtherincreasingthecementitesaredissolvedandM2Ccarbides,β-NiAlintermetallicsandreverseaustenitebegintoprecipitate.Thetensilestrengthandyieldstrengthachievethepeakvalueat470℃,490℃respectively.Thetestedsteelachieveatensilestrengthof2120MPa,ayieldstrengthof1950MPaandimpactenergyof54J/cm2afteroptimumtemperingat510℃.Whentemperingtemperatureisabove530℃theM2Ccarbidesandreverseausteniteiscoarsening.Aftertemperingat560℃thereverseaustenitereachesthemaximumvolumefractioninpresentwork.

简介：CuprecipitationbehaviorsintwoCu-bearingausteniticantibacterialstainlesssteels,type304andtype317L,weresystematicallystudiedbyusingrelativelysimplemethodsformaterialsanalysis,includingmicro-hardness,electricalresistivity,electrochemicalimpedancespectroscopy,X-raydiffractionanddifferentialscanningcalorimetry.Theresultsindicatedthatafteragingatelevatedtemperature,themicro-hardness,electricalresistivity,electrochemicalimpedanceandlatticeconstantofthesteelwereallvariedatdifferentdegreesduetotheprecipitationandgrowthofCu-richphases.TheresultsalsoshowedthattheheatevolutionduringtheprocessofCuprecipitationcouldbesensitivelydetectedbymeansofdifferentialscanningcalorimetry,obtainningthestartingtemperature,peaktemperature,peakareaoftheCu-richprecipitation,andeventheactivationenergybycalculation.TheresultsconfirmedthattheCu-richphasedprecipitationintheCu-bearingausteniticantibacterialstainlesssteelshouldbeathermalactivationprocesscontrolledbyCudiffusion.AllthematerialsanalysismethodsusedinthisstudycanbemoresimpleandeffectiveforapplicationinR&DoftheCu-bearingantibacterialstainlesssteels.

简介：InfluenceofdifferentcoolingratesonthemicrostructureandtheprecipitationbehaviorofNb-TimicroalloyedsteelwasinvestigatedbyCSLM,OM,SEMandEDS.Theresultsshowthattheprecipitationprocessofcarbonitridescanbein-situobservedbyCSLM,andwiththeincreaseofthecoolingrate,thedistributionofprecipitateschangesfromalongtheausteniticgrainboundariestowithinthegrains.Withtheincreaseofthecoolingrate,theproeutectoidferriticfilmbecomessmallerandsmallerandthendisappears,andtheoriginalausteniticgrainsbecomefinerandfiner.Inordertoobtainnon-filmlikeproeutectoidferritesornon-chainlikeprecipitatesalongtheausteniticgrainboundariesandfinerausteniticgrains,thecoolingrateshouldbeatleast5℃/s.

简介：TheinfluenceofTiandNbonthemicrostructure,mechanicalproperties,andsecond-phaseprecipitationof430ferriticstainlesssteelwasinvestigated.Inadditiontoopticalmicroscopy,transmissionelectronmicroscopyandX-raydiffractionanalyses,tensiletests,andcarbonitrideextractionexperimentswereconductedtoinvestigatethemicroscopicmechanisms.TheresultsshowedthattheprimaryprecipitatesinSUS430ferriticstainlesssteelwereCr23C6,Mn23C6,andCr7C3,andtheprimarystrengtheningmechanismwasprecipitationstrengthening.WhenTiwasaddedseparately,themainprecipitateswereTiCandTiN.However,coarseTiCadverselyaffectedthemechanicalpropertiesofsteel.Whendouble-stabilizedwithTiandNb,coarseTiCwasreplacedbyfineNbC.Thetypeofprecipitationwasaltered,andprecipitationandsolidsolutionstrengtheningoccurred.Therefore,thetensilestrengthandplasticstrainratio（r-value）improvedto433.60MPaand1.37,respectively.

简介：Themicrostructuresandprecipitatesinbasemetalsandheataffectedzones(HAZs)oftwoZr-Bmicroalloyedsteelswerecharacterizedbymeansofopticalmicroscopy(OM),transmissionelectronmicroscopy(TEM)andenergydispersivespectrum(EDS).Ithasbeenfoundthatprecipitatesoftensofnanometersinsizearepresentinthebasemetalsofbothsteels.Theaverageparticlesize,however,intheZr-BsteelwithTiislargerthanthatinthesteelwithoutTi.Afterthermalsimulations,inbothcases,theMnSsulfidescannucleateoncubic(Nb,Ti)(C,N)carbonitridesandnearlysphericalZr-bearingcompounds.TheprecipitatesintheHAZsofbothsteelsarecoarserthanthoseinthebasemetals,intherangesof150-200nmand50-100nmforTiaddedandTi-freesteels,respectively.