DYNAMIC RECRYSTALLIZATION IN HIGH-STRAIN, HIGH-STRAIN-RATE PLASTIC-DEFORMATION OF COPPER

When copper is deformed to high plastic strain (gamma approximately 3-4) at high strain rates (gamma approximately 10(4) s-1) a microstructure with grain sizes of approximately 0.1 mum can be produced. It is proposed that this microstructure develops by dynamic recrystallization, which is enabled by the adiabatic temperature rise. By shock-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.