Dynamic recrystallization in high-strain, high-strain-rate plastic deformation of copper

Abstract

When copper is deformed to high plastic strain (γ 3 4) at high strain rates (γ 10⁴s^-1 a microstructure with grain sizes of 0.1 μm can be produced. It is proposed that this microstructure develops by dynamic recrystallization, which is enabled by the adiabatic temperature rise. By schock-loading the material, and thereby increasing its flow stress, the propensity for dynamic recrystallization can be enhanced. The grain size-flow stress relationship observed after cessation of plastic deformation is consistent with the general formulation proposed by Derby [Acta metall. mater.39, 955 (1991)]. The temperatures reached by the specimens during dynamic deformation are calculated from a constitutive equation and are found to be, for the shock-loaded material, in the 500-800 K range; these temperatures are consistent with static annealing experiments on shock-loaded specimens, that show the onset of static recrystallization at 523 K. A possible recrystallization mechanism is described and its effect on the mechanical response of copper is discussed.