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1、Dynamicallyreinforcedheterogeneousgrainstructureprolongsductilityinamedium-entropyalloywithgigapascalyieldstrengtha,1a,1a,bac,2a,b,2MuxinYang,DingshunYan,FupingYuan,PingJiang,EvanMa,andXiaoleiWuabStateKeyLaboratoryofNonlinearMechanics,InstituteofMechanics,ChineseAcade
2、myofSciences,100190Beijing,China;SchoolofEngineeringScience,cUniversityofChineseAcademyofSciences,100049Beijing,China;andDepartmentofMaterialsScienceandEngineering,JohnsHopkinsUniversity,Baltimore,MD21218EditedbyWilliamD.Nix,StanfordUniversity,Stanford,CA,andapprovedJ
3、une4,2018(receivedforreviewMay6,2018)Ductility,i.e.,uniformstrainachievableinuniaxialtension,12),twinningbecamedifficultinUFGgrains,and,atroomtem-diminishesformaterialswithveryhighyieldstrength.Evenforperature,strainhardeningremainedinadequatetosustainuni-theCrCoNimed
4、ium-entropyalloy(MEA),whichhasasimpleface-formelongationaftertheMEAyieldsat>1GPa(3).Ingeneral,centeredcubic(FCC)structurethatwouldbodewellforhighductility,plasticity-enhancingmechanismsinlow-SFEalloyssuchasphasethefinegrainsprocessedtoachievegigapascalstrengthexhaustt
5、hetransformation[transformation-inducedplasticity(TRIP)](10,strainhardeningabilitysuchthat,afteryielding,theuniformtensile30–33)andtwinning[twinning-inducedplasticity(TWIP)](1,2,strainisaslowas∼2%.Herewepurposelydeploy,inthisMEA,a34–41)alllosetheirpotencyinUFGandNGstr
6、uctures(34,35,three-levelheterogeneousgrainstructure(HGS)withgrainsizesspan-42,43).ningthenanometertomicrometerrange,impartingahighyieldHereweadvocateastrategygenerallyapplicableforsingle-strengthwellinexcessof1GPa.Thisheterogeneityresultsfromthisphaselow-SFEalloys,to
7、provideadequatestrainhardeningtoalloy’slowstackingfaultenergy,whichfacilitatescornertwinsinre-delaynecking.TheCrCoNiMEAisagoodmodeltoworkwith,crystallizationandstoresdeformationtwinsandstackingfaultsduringforsettinganexampleforsuchalloys.ThekeyideaunderlyingSCIENCESte
8、nsilestraining.Afteryielding,theelastoplastictransitionthroughourmicrostructuraldesignisasfollows.Weintentionallypushloadtra