On the Shock-Induced Structures in Copper

Abstract

Investigation of copper under shock loading is a subject of current attention for a long time. Owing to simplicity of crystal lattice this material is considered as a convenient test material. However, despite the extensive research many aspects of shock-induced structure formation in this material remain largely unknown. Specifically, it concerns to nucleation of localized structures at the mesoscale [1]. During the shock loading of M3 copper (grain size of 150 ÷ 350 μm, Fig. 1a) within narrow strain rate region of 5 × 10⁶÷5.7 × 10⁶ s⁻¹, the chaotically distributed 3D formations of 5 ÷ 30 μm in diameter were found to be nucleated. In Fig. 1b the SEM image of copper structure after uniaxial shock loading at the impact velocity of 500 m/s is presented. One can see chaotically distributed orthogonal networks of shear bands the size of which ranges within 5 ÷ 30 μm. The formations are the 3D networks composed from shear bands of 50 ÷ 100 nm spacing. Morphological features of 3D structures indicate on crystallographic mechanism of their nucleation, whereas a positive correlation between dimensions of structures and impact velocity allows to consider them as “domains of localized deformation” or 3D structures.