Melting and Solidification

Abstract

Arguably the most interesting material modifications by laser irradiation are those involving melting and solidification. Melts have high atomic mobilities and usually unlimited solubilities, enabling structures that are simply not available from pure solid-state reactions. Examples range form nearperfect crystals, intricately structured alloys and composites to glassy metals. The basic sequence that produces this variety of structures under transient laser irradiation is always the same: Melting of a surface layer and redistribution of atoms in the melt, followed by more or less rapid solidification. We shall summarize this basic sequence as laser remelting. There are two parameters which largely determine the structure resulting from a laser remelting process: the composition of the melt and the velocity of the solid-liquid interface.