Dislocation me diate d dynamic tension-compression asymmetry of a Ni_(2)CoFeV_(0.5)Mo_(0.2) medium entropy alloy  

作　　者：Ao Meng Xiang Chen Yazhou Guo Yiping Lu Yonghao Zhao 

机构地区：[1]Nano and Heterogeneous Materials Center,School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing 210094,China [2]School of Aeronautics,Northwestern Polytechnical University,Xi’an 710072,China [3]Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province),School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024,China

出　　处：《Journal of Materials Science & Technology》2023年第28期204-218,共15页材料科学技术（英文版）

基　　金：the National Key R&D Program of China(No.2017YFA0204403);the National Natural Science Foundation of China(Nos.51971112 and51225102);the Fundamental Research Funds for the Central Universities(No.30919011405);X.Chen would like to acknowledge the finan-cial support from the National Natural Science Foundation of China(Nos.52001165 and 51931003);the Natural Science Foundation of Jiangsu Province,China(No.BK20200475),and the Fundamen-tal Research Funds for the Central Universities(No.30921011215).

摘　　要：Although tension-compression(T-C)asymmetry in yield strength was rarely documented in coarse-grained face centered cubic(FCC)metals as critical resolved shear stress(CRSS)for dislocation slip differs little between tension and compression,the T-C asymmetry in strength,i.e.,higher strength when loaded in compression than in tension,was reported in some FCC high entropy alloys(HEAs)due to twinning and phase transitions activated at high strain regimes in compression.In this paper,we demonstrate a reversed and atypical tension-compression asymmetry(tensile strength markedly exceeds compressive strength)in a non-equiatomic FCC Ni_(2)CoFeV_(0.5)Mo_(0.2) medium entropy alloy(MEA)under dynamic loading,wherein dislocation slip governs dynamic deformation without twins or phase transitions.The asymme-try can be primarily interpreted as higher CRSS and more hard slip modes(lower average Schmid factor)activated in grains under dynamic tension than compression.Besides,larger strain rate sensitivity in dy-namic tension overwhelmingly contributes to the higher flow stress,thanks to the occurrence of more immobile Lomer-locks,narrower spacing of planar slip bands and higher dislocation density.This finding may provide some insights into designing MEAs/HEAs with desired properties under extreme conditions such as blast,impact and crash.

关 键 词：Medium entropy alloy Dynamic deformation Tension-compression asymmetry Slip trace analysis EBSD and TEM 

分 类 号：TG139[一般工业技术—材料科学与工程]