Microstructural refinement of duplex stainless steels.pdf

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1、MicrostructuralrefinementofduplexstainlesssteelsB.SoyluandR.W.K.HoneycombeTheexperimentalresultsofaninvestigationofachemical(alloying)andaphysical(deformation)methodforrefiningthemicrostructureofduplexstainlesssteelsaredescribed.Thechemicaltechniqueinvolvesalloyingwi

2、thcopper.When3wt-%Cuisaddedtoa30Cr-8Nisteel,itwasfoundthatthecopperprecipitation(whichismorerapidthanthatofaustenite)takesplacewithamultitwinnedmorphology.Thesubsequentferrite-austenitetransformationnucleatedonthefinelydispersedcopperparticlesresultsinafine,homogeneo

3、uslydistributed,twinnedaustenitemorphology.Copperparticlesalsohelpedtherefinementoftheaustenitebypinningtheinterphaseinterfaces.Anotherwayofrefiningthemicrostructureisthroughcolddeformation.Asquenchedfullyferriticsteelwith30%Crand8%Niwascoldrolledbyvariousamountsanda

4、gedattemperaturesbelow1000°C.Onaging,partialrecoveryprecededtheaustenitetransformationandnucleationoccurredmainlyonsubgrainboundaries,thusresultinginarefinedmicrostructure.MST/1221©1991TheInstituteofMetals.Manuscriptreceived7March1990;infinalform14June1990.Theauthors

5、areintheDepartmentofMaterialsScienceandMetallurgy,UniversityofCambridge.Becauseofthehighalloycontent,thesteelswerehomogen-Introductionisedusinghighannealingtemperatures(1100°C)forlongtimes(1-2d).ThespecimensweresolutiontreatedforDuplexstainlesssteelscombinetheattract

6、ivepropertiesof10minat1300°C;theywerethenagedeitherbydirectfullyausteniticandfullyferriticstainlesssteelsandpossesstransfertomoltenmetalbathsorfurnaces,orbyfirstpropertieswhichcannotbeobtainedwitheithersinglequenchingintowaterfollowedbyaging.Theuseofthinphasemicrostr

7、ucturealone.Suchaduplexstructure(ofstripspecimensenabledhighquenchingratestobeausteniteandferrite)combinesthetoughnessandweld-achieved.Forthedeformationexperiments,thewaterabilityofaustenitewiththestrength,corrosionresistance,quenchedfullyferriticstripswerecoldrolled

8、toproduceandstresscorrosioncrackingresistanceofferrite,andinreductionsof5,10,25,and50°/0inthickness.Becauseofadditioncanhaveattract