Martensitic transformation induced by void defects in the B2-CuZr crystal structure: an atomistic analysis

Abstract

ABSTRACT Molecular dynamics simulations were carried out to perform tensile tests on B2-CuZr nanofilms at 1 K with a single spherical void defect. Six different samples were considered: a void-free one and five others with a single void with the radius ranging from 3 to 15 Å. In the void-free sample, martensitic transformation was promoted from the top and bottom surfaces, whereas in the other samples, the transformation initiated from the void surface. Moreover, the yield stress decreased as the void size increased. An atomic-level analysis revealed that, prior to the martensitic transformation, the Cu atoms at the void surface were subjected to 34% higher average von Mises stress than the Cu atoms at the top and bottom surfaces. This remarkable difference led to the rearrangement of Cu atoms at the void surface, promoting transformation bands that decreased the overall stress in the system. The reduction in yield stress with the void radius was observed at 300 K, but exhibiting limited phase transformation, failing at lower strains.