Experimental and numerical studies on phase change under dynamic loadings: application to Tin.

Polymorphic (structural) phase transformations of metals under dynamic high pressures is an area of fundamental scientific research at CEA which are studied through both experimental and theoretical/computational means. Experiments have long suggested that non-equilibrium behavior (kinetics) is an important part of the dynamic compression response of materials undergoing phase transformations. Both this deeper understanding, and quantitative data on specific metals, are needed to improve material models used in state-of-the-art hydrocodes. Only in recent years have experimental capabilities advanced sufficiently enough, in terms of diagnostics as well as drivers, that kinetics effects in dynamic phase transformations can begin to be quantified in a more rigorous manner. Empirical kinetic models can in a lot of cases reproduce the experimental velocity profiles but without clearly identifying the nature of the transition.
At CEA, we have developed preheating devices for gas gun and for HPP driver a promising testing on x-ray diffraction under shock. We propose to present our preliminary results to explore the phase diagram of Tin and how these experimental data help to understand kinetic models and EOS.