Amorphization under shock loading

Abstract

The problem of crystalline to amorphous (c → a) phase transformation, in the context of shock loading, is analyzed. The studies under static pressures show that beyond the stability field of the ambient phase, an amorphous phase may be realized if the kinetic conditions are not favorable to the accessibility of equilibrium phase of higher coordination. The examination of shock results of some of these substances reveals that the so-called “mixed phase” region begins at the pressureswhich are same as that oc c → a transformation in the static experiments. Further the Hugoniot temperatures at these pressures are far lower than required for the realization of the high pressure crystalline phase. From these observations as well as from an understanding gained through static experiments, we infer that these materials amorphize under shock loading. The analysis indicates that the existence of hot-spots is not essential to the formation of diaplectic glass. Instead, it seems to emerge directly from the solid-solid phase transformation, adequately aided by favourable kinetic conditions.