Shock-induced vaporization in metals

Results of well-controlled experiments on shock-induced vaporization studies in zinc, indium, and aluminum are presented. A titanium alloy impact at a velocity of 10.4 km/s will melt these materials totally. The expansion products upon release will consist of liquid–vapor mixtures. The ratio of liquid to vapor in the mixture depends on the material and also on the degree of expansion upon release. The impact generated debris propagates a gap dimension up to 125 mm before it stagnates against a stationary witness plate. The non-uniform spatial loading on the witness plate is determined using multiple velocity interferometers. Radiographic measurements of the debris cloud are also taken before it stagnates against the witness plate. Both radiographic and the velocity interferometer measurements suggest lateral and axial expansion. We have identified that the kinetics of the vaporization process can be related to the energy of the material shocked to the high-pressure state. In particular, the energy E of the material in the shocked state is expressed in units of the energy Ev required to vaporize a gram of material from room temperature. Results of these experiments indicate that the rate of vaporization is strongly dependent on E/Ev as it is increased by an order of magnitude from 1 to 10.