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1、MechanicsofTime-DependentMaterials3:1–13,1999.(C)1999KluwerAcademicPublishers.PrintedintheNetherlands.CreepBehaviorofDispersion-HardenedAluminumMaterials弥散硬化铝的蠕变行为I.KROPFL,O.VOHRINGERandE.MACHERAUCHInstitutfürWerkstoffkundeI,UniversitatKarlsruhe,Postfach6980,D-76128Karlsruhe,Germany;E-
2、mail:otmar.voehringer@mach.uni-karlsruhe.de(Received9September1998;acceptedinrevisedform3March1999)Abstract.Dispersion-hardenedaluminummaterialsofpurealuminumwithextremelyfineoxideandcarbidedispersionsandveryfinegrainsizeswerecreep-deformedundercompressiveloadingsbetween573and773K.Thec
3、reepbehavioroftheinvestigatedmaterialsisinfluencedbytime,temperature,stresslevelandmicrostructure.Anincreasingcontentofdispersionscausesincreasingthresholdstressesσthandresistancesagainstcreep.TheNortonplotsoftheminimumcreeprateε˙minversusstressσarecharacterizedbyextremelyhighstressexp
4、onentsn.OnthebasisofthethresholdconceptItisdemonstratedthatthesamediffusionprocessdominatesinthedispersion-hardenedalu-minummaterialsasinpurealuminum.Theirtruestressexponentsn*astheslopesofthebestfitlinesofthelogε˙minversuslog(σ–σth)arecloseto5.Thethresholdstressdecreasesconsiderablywi
5、thincreasingtemperatureduetothethermallyactivatedrecoveryoflong-rangeinternalbackstressesofquasi-planardislocationstructuresonthegrainboundaries.Keywords:backstress,creep,dislocation,dispersion,grainboundary,Nortonplot,particleharden-ing,reaction-milling,thresholdstress,workhardening1.
6、IntroductionThemechanicalbehaviorofaluminummaterialsistime-dependentandinfluencedbymicrostructure,stressstateandtemperature.FortemperaturesT>0.4Ts(Ts=solidustemperatureinK)theextentofthetime-dependenceofthestress-strainresponseincreaseswithincreasingtemperatureduetodiffusion-controlled
7、deform-ationmechanisms.Dispersion-hardenedaluminummaterialsareexpectedtohaveconsiderablyimprovedmaterialpropertiesatservicetemperaturesabove573Kcomparedtoprecipitation-hardenedaluminiumalloysduetothethermodynam-callystableparticles.Theyaredistinguishedfromconventionalaluminumal-loysb
