Effect of initial twins on mechanical properties of additive manufacturing CoCrNi alloy and molecular dynamic simulation

The influence of twins on laser additive CoCrNi MEA was analyzed by experiments and molecular dynamic simulation. Results showed that the traditional laser additive CoCrNi MEA was prone to slip in the (111) direction. EBSD analysis showed an obvious 60°(111} axial angle pair relationship, which is related to the slower cooling rate. The results of molecular dynamic simulation showed that the yield strength of CoCrNi MEA increases first and then decreases, and the material has a critical twin density. When the twin density is less than the critical twin density, the strength of the material increases due to the thinning effect of the twin boundary on the grain. When the twin density is greater than the boundary twin density, the nucleation and proliferation of the twin boundary and the junction of the two become the dominant factors of the material deformation. When the twin density is far from the critical value, the twin spacing becomes smaller, the dislocation sources increase, the dislocation nucleation and proliferation increase, and the strength of the material decreases.