Fig. 1 a Supercells with six (111) atomistic planes and twelve atoms utilized in the calculation of SFE. The left supercell exhibits the perfect FCC structure, whereas the right supercell contains a piece of stacking fault after the application of a shear displacement of 1/6 [11-2] on the top (111) plane. b SFE as a function of Co content in non-equiatomic CoCrNi MEA. c Gibbs free energy difference ΔEHCP-FCC as a function of Ni content

Fig. 2 Microstructure of Ni28 MEA before tensile tests. a IPF images showing complete recrystallization structure and high-density annealing twin; b grain size and twin fraction; c EBSD phase maps showing single FCC structure; d TEM image of annealing twin; and e SEM-EDS maps showing uniform distribution of Co, Cr, and Ni elements

Fig. 3 a Mechanical behavior of the Ni28 MEA, the inserted image is strain-hardening rate as a function of true strain and b comparison of tensile properties between the present MEA and other TWIP effect CoCrNi MEA reported in the literature [26,27,28,29,30,31,32,33,34]

Fig. 4 Deformation morphology and damage microstructures after tension. a Phase transition indicated by EBSD phase maps; b high-resolution (HR) TEM image showing HCP lamellas after fracture; c the SAED pattern of b; HCP network shown by d IPF map; e phase maps; and f KAM maps

Fig. 5 a ECC images showing high-density HCP networks; b HCP lamella as a channel for dislocation movement; and c atomic level image displayed L-C lock and FFT pattern on inset indicated stacking-fault features