Bidirectional transformations,which are achieved by triggering both dynamic forward transformation from the face-cen-tered-cubic(fcc)austenite to the hexagonal-close-packed(hcp)martensite and the reverse transformation from martensite to austenite during cold deformation,have been previously reported in FeMnCoCr-based high-entropy alloys(HEAs).This leads to the permanent refinement of microstructure and hence enhances the work-hardening capacity of alloys.In order to reveal the microscopic mechanism of the reverse transformation in HEAs under deformation,the effect of the sample aspect ratio,i.e.,Z/X,on the evolution of deformation systems in the equi-atomic FeMnCoCrNi alloy with[110]orientation during uniaxial tensile loading along the Z direction is investigated by atomic simulations in this study.When the aspect ratio is 0.5,the reverse transformation is more significant compared with other models,while a good plasticity can still be maintained.We then compare the micromechanical behavior of three fcc single crystals,i.e.,FeMnCoCrNi,FeCuCoCrNi,and pure Cu.The results show that the stacking fault energy plays a major role in the activation of different deformation mechanisms;however,the lattice distortion in the HEA does not significantly affect the activation of deformation systems.Furthermore,for all materials dislocation slip leads to the softening,while strain hardening is attributed to the initiation of multiple defor-mation mechanisms.The Shockley partials slip leads to bidirectional phase transition,twinning and detwinning in the three materials.Thus,the reverse transformation can occur in all metallic materials where the fcc to hcp phase transformation is the dominant deformation mechanism.These findings contribute to an in-depth understanding of the deformation mechanism in fcc-structured materials under severe plastic deformation and provide theoretical guidance for the design of alloys with superior strength-plasticity combinations.

Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education),School of Material Science and Engineering,Northeastern University,Shenyang 110819,China;State Key Lab Rolling&Automat,Northeastern University,Shenyang 110819,China

[1]Hai-Feng Zhang;Hai-Le Yan;Feng Fang;Nan Jia-.Reverse Transformation in[110]-Oriented Face-Centered-Cubic Single Crystals Studied by Atomic Simulations)[J].金属学报（英文版）,2022(10):1631-1640

FeMnCoCr,FeMnCoCrNi,FeCuCoCrNi,partials,detwinning

Reverse,Transformation,Oriented,Face,Centered,Cubic,Single,Crystals,Studied,by,Atomic,Simulations,Bidirectional,transformations,which,achieved,triggering,both,dynamic,forward,from,face,cen,cubic,fcc,austenite,hexagonal,close,packed,hcp,martensite,reverse,during,cold,deformation,have,been,previously,reported,high,entropy,alloys,HEAs,This,leads,permanent,refinement,microstructure,hence,enhances,work,hardening,capacity,In,order,reveal,microscopic,effect,sample,aspect,ratio,evolution,systems,equi,atomic,orientation,uniaxial,tensile,loading,along,investigated,simulations,this,study,When,compared,other,models,while,good,plasticity,still,maintained,We,then,micromechanical,behavior,three,single,crystals,pure,results,show,that,stacking,fault,energy,plays,major,role,activation,different,mechanisms,however,lattice,distortion,does,not,significantly,affect,Furthermore,materials,dislocation,slip,softening,strain,attributed,initiation,multiple,Shockley,bidirectional,phase,transition,Thus,occur,metallic,where,dominant,These,findings,contribute,depth,understanding,structured,severe,provide,theoretical,guidance,design,superior,strength,combinations

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