Hardening of metals and alloys during shock compression

The influence of shock compression on the spall strengths of copper, brass, nickel, stainless steel, armco iron, and titanium nickelide Ti$_{51.1}$Ni$_{48.9}$ is studied in the pressure range 2–80 GPa at a strain rate higher than 10$^4$ s$^{-1}$ by recording wave profiles with a VISAR laser velocimeter and subsequent analysis. The strengths of the metals subjected to strong twinning during shock compression are shown to increase with the pressure in a shock wave, and the dependence of the strength on the shock pressure has a threshold character due to thermal softening at the maximum shock wave amplitude. The metals that undergo phase transformations have a more complex relation between the spall strength and the shock compression intensity.