The kinetics of the phase transitions occurring in solid materials under strong compression are an issue of considerable interest, which can be studied using dynamic loading processes. Here, we investigate the phase transformation behavior of quartz under laser-induced shock compression of a very short duration (nanosecond order). Time-resolved measurements, coupled with simple computer simulations, have been used to characterize the pressure pulse induced in the samples. Recovery shots have been performed for postshock spectroscopy, that has revealed permanent structural changes of various types, depending on the experimental conditions (loading pressure, sample thickness, and initial temperature). The results, which differ notably from observations reported under quasi-static compression or longer pulsed loads (microsecond order), suggest a partial amorphization of the shocked samples, as well as the formation of a structure that can be compared to known orthorhombic high-pressure phases. They provide an insight into the early stages of the shock-induced transformation mechanisms in this widely studied material.

Iron samples of different thicknesses have been submitted to laser shocks of short duration. Transmitted wave measurements have been performed by means of polymeric piezoelectric transducers. The records indicate a decrease of the elastic precursor amplitude with increasing propagation distance, as well as a stress relaxation behind the elastic wave front. These features were already observed in shock-loaded iron, but this paper extends the experimental data to a previously unexplored range of thin targets and high strain rates. Postshock examinations of the recovered specimens reveal significant twin formation. Computer simulations of the experiments have been made using a constitutive model from the literature, including a theoretical description of rate-dependent twinning. The ability of that model to predict the experimental results has been tested. A correct overall agreement has been obtained, except for some discrepancies which have been discussed.

First absolute equation of state measurements obtained for iron with laser driven shock waves are presented. The shock velocity and the free surface velocity of compressed iron have been simultaneously measured by using a VISAR diagnostic, and step targets. The pressure range 1–8 Mbar has been investigated, which is directly relevant to planetary physics. The experiments have been performed at the Laboratoire pour l’Utilisation des Lasers Intenses of the Ecole Polytechnique.