马氏体不锈钢激光焊后热处理Improvement of mechanical properties of stainle

The response of stainless maraging steel weldments to post-weld ageing treatment has been investigated. Post-weld ageing was performed at five different temperaturesMetallographic characterization of weldment revealed three zones, namely fusion zone, heat-affected zone (HAZ) and unaffected parent metal zone. Hardness and tensile properties were evaluated after ageing at different temperatures.

Improvementofmechanicalpropertiesofstainlessmaragingsteellaserweldmentsbypost-weldageingtreatments

JianAn ,FanyanMeng,XiaoxiaLv,HaiyuanLiu,XiaoxiGao,YuanboWang,YouLu

KeyLaboratoryofAutomobileMaterials,MinistryofEducation,DepartmentofMaterialsScienceandEngineering,NanlingCampusofJilinUniversity,Changchun130025,People’sRepublicofChina

articleinfoabstract

Theresponseofstainlessmaragingsteelweldmentstopost-weldageingtreatmenthasbeeninvestigated.Post-weldageingwasperformedat vedifferenttemperatures,viz.,420°C,460°C,500°C,540°C,and580°C.Metallographiccharacterizationofweldmentrevealedthreezones,namelyfusionzone,heat-affectedzone(HAZ)andunaffectedparentmetalzone.Hardnessandtensilepropertieswereevaluatedafterageingatdifferenttemperatures.HardnessinHAZandfusionzonevariedwithageingtemperaturedifferentlyfromthatoftheparentmetal;itbecamehigherinHAZandfusionzonethaninparentmetalzoneabove420°C.Amongtheappliedageingtreatments,ageingat460°Cachievedthehighesttensilestrength.Agraphwasconstructedfordeterminationoffracturelocationandpost-weldheattreatmentef ciencybasedonexperimentalresults,usinghardnessratioofHAZtothetreatedparentmaterialandhardnessratioofHAZtotheas-receivedparentmaterial.

Ó2012ElsevierLtd.Allrightsreserved.

Articlehistory:

Received4January2012Accepted13March2012

Availableonline28March2012Keywords:

A.FerrousmetalsandalloysD.WeldingE.Mechanical

1.Introduction

Forseveraldecades,twomajortypesofmaragingsteels,Fe–NisystemandFe–Cr–Nisystemalloys,havebeendevelopedandusedindefense,power,andothercommercialindustriesduetotheirsuperiorpropertiessuchasultra-highstrength,excellentfracturetoughness,goodmachiningpropertiesandweldability[1,2].ThemostcommonlyusedFe–Nimaragingsteelcompositionisbasedon18wt.%Niwithsigni cantlevelsofCo(8–13wt.%),whilethesubsequentlydevelopedCo-freemaragingsteelscontainFe,Ni,MoandTi[3–7].ThecompositionofFe–Cr–Nimaragingsteelsisbasedon10.2–16wt.%CrwithconsiderablelevelsofNi(3.9–10.8wt.%)andotherelementssuchasMo,Ti,AlandCu.Fe–Cr–Nimaragingsteelusuallypossessesgoodcorrosionresis-tance[8–12].Itiswellknownthattheultra-highstrengthofmar-agingsteelsismainlyattributedtotheprecipitationofdenselydistributed neintermetallicprecipitatesinamartensiticmatrix,whichstrengthenthealloysthroughOrowan-typemechanism.Typically,thiskindofmicrostructureisadjustedbyasimpletwo-stepheat-treatmentprocesswhichconsistsofsolutionannealingtoproduceacompletemartensiticmatrix,andsubse-quentlyageingatintermediatetemperatures(400°Cto600°C)tocauseprecipitationhardening.Theageingbehaviourofmarag-ingsteelshasbeenextensivelyinvestigatedoverrecentdecades.Bymeansofhigh-resolutionmethods,suchasatomprobeCorrespondingauthor.Tel.:+8643185095874;fax:+8643185095876.

E-mailaddress:anjian@http://www.77cn.com.cn(J.An).

0261-3069/$-seefrontmatterÓ2012ElsevierLtd.Allrightsreserved.http://www.77cn.com.cn/10.1016/j.matdes.2012.03.020

tomography(APT),transmissionelectronmicroscopyandsmall-angleneutronscattering,thesizeandchemicalcompositionofnanometer-sizedclusterofprecipitatesareidenti edinnumerousmaragingsteels.Forexample,18%Nimaragingsteelsexhibitorderedandcoherentphasessuchasl,SandX(<450°C),Ni3(Mo,Ti),andFe2Mophases(450–500°C),andausteniteprecipita-tion(500°C-As)[13–16].ForFe–Cr–Ni–Al–Tistainlessmaragingsteel,whichcontainsinaddition0.5–1.0at.%Si,asphericalG-phasewiththechemicalcompositionofTi6Si7Ni16,andarod-shapedNi3(Ti,Al)phasewereobserved[17,18].

Weldabilityisauniquepropertywhichmakesmaragingsteelsespeciallysuitableforprocessinginaviationandspaceindustry,sinceweldingofmaragingsteelscanbeperformed,withoutpre-heating,byprocessessuchaselectronbeam,laserwelding,andsubmergedarc[19–22].Ramanaetal.[23]studiedthemicrostruc-tureandresidualstressdistributionofdissimilarelectronbeamweldof18Nimaragingsteelandmediumalloymediumcarbonsteel,itwasobservedthattheresidualstressdistributionwouldbemorecompressiveifthemaragingsteelwasinsoftcondition.Amongtheseprocesses,gastungsten-arcweldingiswidelyutilizedinviewoftheconsistencyofweldequalityandoverallef ciency[24].Therearevariousreportspublishedrecentlyongastung-sten-arcweldingofmaragingsteels.Asthe18Nimaragingsteelsrepresentmajorityofmaragingsteelproducts,theassociatedlowtensilepropertyandtoughnessrisingfromprematureofrevertedaustenite,crackinginheat-affectedzone(HAZ)immediatelyadja-centtofusionlineassociatedwithgastungsten-arcweldingwerethesubjectsofseveralreportsintheliterature.Shamanthaetal.

The response of stainless maraging steel weldments to post-weld ageing treatment has been investigated. Post-weld ageing was performed at five different temperaturesMetallographic characterization of weldment revealed three zones, namely fusion zone, heat-affected zone (HAZ) and unaffected parent metal zone. Hardness and tensile properties were evaluated after ageing at different temperatures.

J.Anetal./MaterialsandDesign40(2012)276–284277

[25]investigatedmicrostructurechangesduringweldingandsub-sequentpost-weldageingof18Nimaragingsteelatvarioustem-peraturesandconcludedthatpronouncedsegregationofTiandMoelementsalonginterdendriteandintercellularboundariesintheweldmetalledtoaustenitereversionattemperaturesmuchlowerthaninunweldmaterial.Similarly,Reddyetal.[26]reportedthatsolutionizedtreatmentof18Nimaragingsteelweldmentsat815°CcouldnotremovethesegregationofTiandMoelements,onlyhomogenizationtreatmentat1150°Csucceeded,andconse-quentlyresultedinoptimumtensileproperties. …… 此处隐藏：28637字，全部文档内容请下载后查看。喜欢就下载吧 ……