Strength-ductility synergy of additively manufactured (CoCrNi)₈₇Al₁₃  medium entropy alloy with heterogeneous multiphase microstructure 

Mengyao Zheng ^a , Chuanwei Li ^a,* , Zhenhua Ye ^a , Xinyu Zhang ^a , Xudong Yang ^a , Qing Wang ^c , Jianfeng Gu ^a,b,* 

^a Institute of Materials Modification and Modelling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

^b Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China

^c Laboratory for Microstructures, Institute of Materials, Shanghai University, Shanghai 200444, China 

^* Corresponding authors at: Institute of Materials Modification and Modelling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.

Abstract

In this study, a (CoCrNi)87Al13 medium-entropy alloy was fabricated by using laser-based directed energy deposition (L-DED). The yield strength and ultimate tensile strength of the (CoCrNi)87Al13 alloy were improved by 67% and 59%, respectively, compared with those of a L-DEDed CoCrNi alloy, and the ultimate elongation remained at 24%. A heterogeneous multiphase microstructure with multiscale ordered/disordered body-centered cubic phases was obtained by adding Al during the rapid solidification and thermal cycle history of the L-DED. The heterogeneous multiphase microstructure was closely correlated with the mechanical performance improvement, deformation, and fracture mechanisms of the alloys.