简介:Thecreepmechanismofas-castMg-6Al-6Ndalloywasstudied.Thestressexponentforcreepis5.8undertheappliedstressesof50-70MPaat175°C.Theactivationenergyforcreepis189kJ·mol-1undertheappliedstressof70MPaintherangeof150-200°C.Thetruestressexponentandthresholdstressforcreeparecalculatedas4.96and10.2MPa,respectively.Thetruestressexponentindicatesthatitscreepmechanismbelongstothedislocationclimb-controlledcreep,whichisinagreementwiththemicrostructurechangesbeforeandaftercreep.ThehighvalueforstressexponentisattributedtotheinteractionofAl11Nd3phasewithdislocations.Theactivationenergyismorethantheself-diffusionactivationenergyofMg,whichisattributedtotheloadtransfertakingplacefromthematrixtoAl11Nd3phaseduringcreep.
简介:DD6alloywasbondedbytransientliquidphase(TLP)diffusionbonding.Themaincompositionsoftheinterlayeralloyemployedweresimilartothoseofthebasemetal,DD6,andacertainamountofelementBwasaddedasthemeltingpointdepressant.Theresultsshowthatitisdifficulttoobtainthejointswiththemicrostructurescompletelyhomogeneous.ForthejointTLPdiffusionbondedat1290℃for12h,abouthalfareasofthebeampossessedαγ+γ′microstructure,nearlyidenticalwiththatofthebasemetal,andtheotherlocalareasconsistedofT-solution,borides,etc.Prolongingthebondingtimeto24h,theinhomogeneousareasinthejointreduced,andthejointpropertyimproved.Thejointstress-rupturestrengthat980℃and1100℃reached90%-100%and70%-80%ofthoseofthebasemetalrespectively.
简介:Theeffectsofprocessparametersonthemicrostructuralevolution,includinggrainsizeandvolumefractionoftheαphaseduringhotformingofaTC6alloywereinvestigatedusingcompressiontests.Experimentswereconductedonthematerialwith(α+β)phasesatdeformationtemperaturesof800,860,920,and950°C,strainratesof0.001,0.01,1,and50s-1,andheightdirectionreductionsof30%,40%,and50%.Afterreachingapeakvaluenear920°C,thegrainsizeandvolumefractiondecreasewithfurtherincreaseofdeformationtemperature.ThestrainrateaffectsthemorphologiesandgrainsizeofαphaseoftheTC6titaniumalloy.Atalowerstrainrate,theeffectofthestrainrateonthevolumefractionisgreaterthanthatatahigherstrainrateundertheexperimentalconditions.Theeffectsofthestrainrateonthemicrostructurealsoresultfromdeformationheating.Thegrainsizeoftheαphaseincreaseswithanincreaseinheightdirectionreductionafteranearlydrop.Theeffectofheightdirectionreductiononthevolumefractionissimilartothatofthegrainsize.AlloftheopticalmicrographsandquantitativemetallographyshowthatdeformationprocessparametersaffectthemicrostructureduringhotformingoftheTC6alloy,andacorrelationbetweenthetemperature,strain,andstrainrateappearstobeasignificantfuzzycharacteristic.