Shock-induced phase transitions in metals: Recrystallization of supercooled melt and melting of overheated solids

Abstract

Melting shock waves in aluminum were studied using a moving window molecular dynamics (MW-MD) technique. It was found that shock compression in the [100] crystallographic direction leads to the formation of an overheated metastable solid state. This state is located on an extension of the solid branch of the T-P Hugoniot above the melting line. The melting of the overheated crystal is accompanied by a temperature decrease in the downstream flow behind the shock front. By contrast, shock compressions in the [110] and [111] directions result in a so-called "cold" melting that takes place below the melting line. This metastable supercooled state, lying on the extension of liquid branch of the T-P Hugoniot below the melting line, eventually undergoes a recrystallization associated with a temperature increase in the after-shock flow. © 2012 American Institute of Physics.