Superelasticity and the Propagation of Shock Waves in Crystals

The separation of a shock wave into an elastic precursor and a plastic wave is a characteristic phenomenon occurring only in solid media. The existence of the elastic shock wave at pressures p approximate to 10 GPa, which is one or two orders of magnitude higher than the dynamic elastic limit, has been detected in recent numerical calculations and a femtosecond laser experiment. The plastic shock wave has no time to be formed in these ultrashort waves at p approximate to 10 GPa. The processes of the formation and propagation of the elastic and plastic waves in aluminum at higher pressures obtained by means of femtosecond lasers have been analyzed in this work. It has been found that the elastic precursor survives even under the conditions when the pressure behind the plastic front reaches a giant value p similar to 1 Mbar at which the melting of the metal begins. It has been shown that superelasticity should be taken into account to correctly interpret the preceding laser experiments.