Shock-induced defects in bulk materials

In this paper examples of the shock-induced defects produced during shock compression which correlate with microstructure / mechanical property changes induced in materials due to shock prestraining are discussed. The characteristics of the shock impulse(peak shock pressure, pulse duration, and rarefaction rate) imparted to the material under investigation and the shock-induced defects produced in numerous metals and alloys are compared with their deformation behavior at ordinary rates of deformation. Examples of the range of defects observed in shock-recovered metals and alloys, include: dislocations, deformation twins, point defects, and residual metastable remnants from pressure-induced phase transformations. Results concerning the influence of interstitial content on the propensity of omega-phase formation and its structure in high-purity and A-70 Ti are presented. The influence of shock-wave deformation on the phase stability and substructure evolution of high-purity (low-interstitial) titanium and A-70 (3700 ppm oxygen) titanium were probed utilizing real-time velocity interferometry (VISAR) and "soft" shock-recovery techniques. Suppression of the alpha-omega pressure-induced phase transformation in A-70 Ti, containing a high interstitial oxygen content, is seen to simultaneously correspond with the suppression of deformation twinning.