Influence of iron anisotropy on phase transition near grain boundary under shock

Abstract

As is well known, iron plays an important role in the fields of national defense and industry, so it is of great significance to study its behavior under dynamic high pressure. As one of the most common defects in metals in nature, grain boundaries have an important influence on the mechanical properties and deformation of materials under shock. This work intends to use large-scale non-equilibrium molecular dynamics simulation to study the influence of iron anisotropy on the phase transition in bicrystal under shock loading. By tracking the local structure, shear stress distribution and morphology characteristics after shock on both sides of the grain boundaries, the factors affecting the response on both sides of the grain boundary are analyzed. Our research result shows that shocking along the non-centrosymmetric grain direction can cause significant differences in the phase transition threshold, path and mode on both sides of the symmetric grain boundary. Especially, the different phase transition dynamic processes on both sides of the sigma11 grain boundary are discussed in detail in this work, which have been rarely discussed in previous studies. Considering the symmetry of the microstructure on both sides of this type of grain boundary, the result of asymmetric shock response is different from people’s inertial cognition. Finally, it is found that the atoms in both models will shift along the direction perpendicular to the shocked direction under shock, indicating that the shock wave generated by the piston method should no longer be simply regarded as one-dimensional when shocked along the non centrosymmetric crystal direction, and the displacement of atoms along the direction perpendicular to the shocked direction is closely related to the symmetry of the crystal, which causes significant differences in shear stress on both sides of the grain boundary and ultimately affects the shock response. This study reveals that the anisotropy of lattice has an important effect on the phase transition on both sides of grain boundaries under shock loading, which can provide theoretical support for the experimental studies of polycrystalline metals and alloys under shock.