Fracture resistance of textured polycrystalline Zr: A simulation study

Abstract

We report the results of large-scale molecular dynamics atomistic simulations of crack propagation in of α-Zirconium. The samples studied are polycrystalline columnar grains of 11–38 nm average diameter, and different textures. The focus is on deformation mechanisms in the crack tip region and the influence of texture, grain size and temperature on the fracture propagation. We found that the [1–100] texture is the most brittle with deformation at the crack tip occurring only through twinning with almost no dislocation activity. The more ductile textures are those where dislocation mechanisms are activated. For the basal orientation we observed <a> dislocations while <c + a> dislocations are dominant for the [11–20] texture. One important observation is that crack propagation can be hindered by the presence of the grain boundaries. As a result, samples with the smallest grain sizes are the more resistant to crack propagation. As expected, higher temperatures imply easier deformation, resulting in more ductile behavior for all orientations. At room temperature and higher, crack propagation occurs mostly intra granularly. However, at 77 K the [1–100] textured sample shows crack propagation through the nucleation of micro-voids ahead of the main crack.