The thermodynamic-pathway-determined microstructure evolution of copper under shock compression

Abstract

Shock-induced structural transformations in copper exhibit notable directional dependence and anisotropy, but the mechanisms that govern the responses of materials with different orientations are not yet well understood. In this study, we employ large-scale non-equilibrium molecular dynamics simulations to investigate the propagation of a shock wave through monocrystal copper and analyse the structural transformation dynamics in detail. Our results indicate that anisotropic structural evolution is determined by the thermodynamic pathway. A shock along the ⟨ 100 ⟩ orientation causes a rapid and instantaneous temperature spike, resulting in a solid–solid phase transition. Conversely, a liquid metastable state is observed along the ⟨ 111 ⟩ orientation due to thermodynamic supercooling. Notably, melting still occurs during the ⟨ 110 ⟩ -oriented shock, even if it falls below the supercooling line in the thermodynamic pathway. These results highlight the importance of considering anisotropy, the thermodynamic pathway and solid-state disordering when interpreting phase transitions induced by shock. This article is part of the theme issue ‘Dynamic and transient processes in warm dense matter’.