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

Abstract

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.

Toward better understanding of the high-pressure structural transformation in beryllium by the statistical moment method

“…Specifically, the enormous shear stress at the shock front may lead to an overproduction of defects in the beryllium sample. 75–77 Therefore, some parts of the beryllium sample may become extremely disordered and fall into metastable states ( e.g. , supercooled liquid).…”

“…75–77 This phenomenon is called “cold melting” because it occurs at T < T m . 75–77 Similar to the equilibrium melting, the cold melting also causes the longitudinal sound speed to decrease sharply. 18…”