Mechanism of formation of cellular dislocation structures during propagation of intense shock waves in crystals

Abstract

The mechanism of formation of a cellular dislocation structure in face-centered cubic (fcc) metal crystals subjected to shock compression at strain rates $\dot \varepsilon$ > 10⁶ s⁻¹ has been considered theoretically within the dislocation kinetic approach based on the kinetic equation for the dislocation density (dislocation constitutive equation). A dislocation structure of the cellular type is formed in the case of a two-wave structure of the compression wave behind its shock front (elastic precursor). It has been found that, at pressures σ > 10 GPa, the dislocation cell size Λ _c depends on the pressure σ and the density ρ _G of geometrically necessary dislocations generated at the shock front according to the relationship Λ _c ∼ ρ ⁻ⁿ _G ∼ σ^−m, where n = 1/4–1/2, m = 3/4–3/2, and m = 1, for different pressures and orientations of the crystal. It has been shown that, in copper and nickel crystals with the shock loading axis oriented along the [001] direction, the cellular structure is not formed after reaching the critical pressures σ _c equal to 31 and 45 GPa, respectively.