Collapse of stacking fault tetrahedron and dislocation evolution in copper under shock compression

The stacking fault tetrahedron (SFT) is frequently observed in irradiated materials, which distinctly affects the mechanical properties of matrix materials. This work focuses on the collapse of SFT and the following dislocation evolution in single crystal copper under shock compression with molecular dynamics simu-lations. Our results reveal the collapse pattern of SFT and its dependence on the shock orientations. The SFT undergoes different metastable structures, e.g., a triangular Frank loop, a semi-faulted SFT, and a truncated SFT with two Frank partial dislocations for [111], [11 ]degrees, and [112 ] over line shock orientation respectively, which provide nucleation sites for dislocation emission. The dependence of dislocation loops and stack -ing faults formed from SFT on the shock intensity is revealed. As the shock intensity increases, the stress relaxation resulting from the structural transformation of SFT becomes more obvious, and the dislocation density increases more rapidly to a higher peak value. The equilibrium values of von Mises stress and dislocation density after long-time evolution also increase. With the increase of initial temperatures, the critical stress for plastic deformation is found to decrease linearly and the reduction in [112 ] over line orientation is much smaller than that in [111] and [11 ]degrees orientations. The dislocation density increases and the stacking faults will decompose into smaller stacking fault pieces to some extent because of thermal fluctuation. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the collapse of stacking fault tetrahedron (SFT) and subsequent dislocation evolution in single crystal copper under shock compression using molecular dynamics simulations. The results show the collapse pattern and shock orientation dependence of SFT, as well as the relationship between shock intensity and dislocation density. Increasing shock intensity leads to a more rapid increase in dislocation density and structural transformation of SFT. Additionally, higher initial temperatures result in a decrease in critical stress for plastic deformation and thermal fluctuation impacts the decomposition of stacking faults.