Simulation study on mechanical properties of gradient-structured nano-polycrystalline Ni

Abstract

The effects of gradient grain size and temperature on the mechanical properties of nanocrystalline nickel were studied by the molecular dynamics method, and the microstructure change process of size gradient nanocrystalline nickel under tensile load was characterized by Common Neighbor Analysis (CNA). The research results show that dislocations tend to generate stress concentration in small-sized grains during stretching, so the plastic deformation of the material always occurs in small-sized grains first. At the same time, through Dislocation Analysis (DXA), it was found that Shockley dislocation is the main factor affecting its mechanical properties, and the interaction between dislocations provides a certain contribution to the strength of the metal. In addition, yield strength, maximum tensile stress, and Young’s modulus all decrease with increasing temperature, and the grain boundary atomic content and the degree of disorder are greatly increased. During the stretching process, the number of dislocations is greatly reduced, which leads to a reduction of their interactions, which is the reason for the reduction of the mechanical properties of the material. The above research results have positive meaning for the design of gradient nanocrystalline materials, and provide reference and help for the improvement of nanomaterial properties.