Effects of grain size distribution on the mechanical response of nanocrystalline metals

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1、ActaMaterialia54(2006)3307–3320www.actamat-journals.comEffectsofgrainsizedistributiononthemechanicalresponseofnanocrystallinemetals:PartIIa,*aabbB.Zhu,R.J.Asaro,P.Krysl,K.Zhang,J.R.WeertmanaDepartmentofStructuralEngineering,UniversityofCalifornia,SanDiego,LaJolla,CA92

2、093,UnitedStatesbDepartmentofMaterialScienceandEngineering,NorthwesternUniversity,Evanston,IL60208,UnitedStatesReceived23December2005;receivedinrevisedform8March2006;accepted12March2006Availableonline19May2006AbstractThemodelofZhuetal.[ZhuB,AsaroRJ,KryslP,BaileyR.Tra

3、nsitionofdeformationmechanismsanditsconnectiontograinsizedistributioninnanocrystallinemetals.ActaMater2005;53(18):4825–38]isfurtherdevelopedandusedtoexploretheeffectofgrainsizeandgrainsizedistribution,alongwiththeinfluenceofmaterialparameters,onthemechanicalresponseofn

4、anocrystallineface-centeredcubicaggregates.Thismodelaccountsforthesimultaneouscontributionsofdeformationmechanismsincludinggrainboundaryemissionofdislocationsand/orstackingfaults,aswellasformechanismssuchasgrainboundaryslidingandfornaturaltransitionsbetweentherelativ

5、edominanceofeach.Theeffectofgraingrowthduringdeformationisalsoquantitativelyassessedviasimulationofrecentlyobtaineddataonindentationtestsinwhichdynamicgraingrowthwasdocumentedthroughthemeasurementofchangesingrainsizedistributionandconcomitantchangesinhardness.Thesimul

6、ationsprovideaplausibledescriptionoftheobservedphenomenologyandfurtherunderscoretheunstablenatureofnanocrystallinegrainsizedistributions.ThepossibilityofincorporatingadditionalpotentialdeformationmechanismssuchasCoblecreep,ashasbeenproposedinothermodels,isdiscussedan

7、dshowntobestraightforwardadditiontothemodel.Recentlyobtaineddataontexturedevelopmentisanalyzedviatexturepre-dictionsforaggregatessubjecttofinitedeformationsviahighpressuretorsion(HPT).Thephenomenologyisassessedspecificallywithregardtothepotentialuseoftexturemeasurement

8、sforconfirmingtheimportanceofcrystallographicmechanismsvs.thosesuchasgrainboundarysliding.Ó2006ActaMaterialiaInc.PublishedbyElsevier