It has been well documented that grain size plays a critical role in the strain hardening behaviors of met-als and alloys.However,the influence of grain size on the strain hardening of high entropy alloys(HEAs)was not fully understood.Here,we report that the grain size not only affects the twinning-induced plasticity(TWIP)effect but also changes the dislocation-based deformation behaviors of face-centered-cubic(fcc)HEAs significantly.The strain hardening and deformation micro-mechanisms of NiCoCrFe and Ni2CoCrFe were investigated using electron channeling contrast(ECCI)analysis.Our results showed that Ni2CoCrFe exhibits a typical three-stage strain hardening behavior and NiCoCrFe shows the fourth stage at high strains due to the TWIP effect.For both NiCoCrFe and Ni2CoCrFe,the increase of grain size leads to a transition of dislocation glide from wavy to planar mode,resulting in a low value and the recovery of strain hardening rate in stage II.The large-grain NiCoCrFe showed a higher strain hardening rate in stage IV due to the promoted deformation twinning.Combining the strain hardening behaviors of the TWIP-NiCoCrFe and the mechanically stable Ni2CoCrFe,we showed that the grain size influences the stage II hardening through tuning dislocation glide mode and the stage IV by tailoring deformation twinning ac-tivity of the Ni-Co-Cr-Fe HEAs.The grain size just affects stages I and III slightly in the current cases.These findings will also provide some insights into the understanding of strain hardening behaviors in other face-centered-cubic HEAs.

Xiaorong Liu;Sihan Jiang;Jianlin Lu;Jie Wei;Daixiu Wei;Feng He

State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China;School of Physics and Electronic Engineering,Linyi University,Linyi 276005,China;Institute for Materials Research,Tohoku University,2-1-1 Katahira,Sendai,Miyagi,980-8577,Japan

材料科学技术（英文版）

[1]Xiaorong Liu;Sihan Jiang;Jianlin Lu;Jie Wei;Daixiu Wei;Feng He-.The dual effect of grain size on the strain hardening behaviors of Ni-Co-Cr-Fe high entropy alloys)[J].材料科学技术（英文版）,2022(36):177-184

NiCoCrFe,Ni2CoCrFe,ECCI

dual,effect,grain,size,hardening,behaviors,entropy,alloys,It,has,been,well,documented,that,plays,critical,role,met,However,HEAs,was,not,fully,understood,Here,report,only,affects,twinning,induced,plasticity,TWIP,but,also,changes,dislocation,deformation,face,centered,cubic,fcc,significantly,micro,mechanisms,were,investigated,using,electron,channeling,contrast,analysis,Our,results,showed,exhibits,typical,three,shows,fourth,strains,due,For,both,increase,leads,transition,glide,from,wavy,planar,mode,resulting,low,value,recovery,rate,large,higher,IV,promoted,Combining,mechanically,stable,influences,through,tuning,by,tailoring,tivity,just,stages,III,slightly,current,cases,These,findings,will,provide,some,insights,into,understanding,other

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