Structural Transformations in the Grain Boundary Region of Nanocrystalline Metals Under Mechanical Loading

Abstract

Molecular dynamics analysis of special features of structural transformations at the grain boundaries (GBs) of nanocrystalline metals with face-centered cubic (FCC) and body-centered cubic (BCC) lattices under shear loads is performed. The objects of the study are nickel and vanadium samples containing symmetric tilt GBs. Shear loading is specified by the displacement of the surface atomic layers parallel to the GB plane at a constant speed. Shear load causes a high-speed GB movement along the normal to the boundary plane. To initiate the GB movement, high stress is required. Periodic boundary conditions prevent the occurrence of the grain rotations. The GB velocity is determined by the shear rate and depends on the grain misorientation angle. It has been found that the GB movement has a jump-like nature and is accompanied by a rapid drop in the internal stresses. Self-consistent structural transformations of atomic planes, through which the high-speed GB movement in a metal occurs, are revealed.