Twin structures in copper after shock and Shockless high-rate loading

The structure of copper formed after high-rate loading up to pressures of 20–80 GPa with a strain rate of 10$^5$–10$^9$ sec$^{-1}$ is considered. In situations with pressures above 20 GPa and strain rates above 10$^6$ sec$^{-1}$, the deformation twins are grouped into packets, which are seen in an optical microscope as parallel bands of localized strains inside individual grains. The number of bands in the structure increases with increasing grain size and strain rate, with decreasing sample temperature, and with increasing period of sample loading. The characteristic time of formation of twin bands in copper is estimated as 0.3 $\mu$sec.