NONEQUILIBRIUM SOLIDIFICATION OF UNDERCOOLED METALLIC MELTS

The non-equilibrium state of an undercooled melt allows the investigat ion of various phenomena involved in the formation of metastable solid phases. The present work reviews the present state of the art in this field. In detail, the thermodynamics of the undercooled melt, nucleat ion and growth processes are discussed, with special emphasis on the c onditions of the formation of metastable states, such as metastable cr ystalline metals, quasi-crystals, metallic glasses, supersaturated sol utions and grain-refined materials. The techniques needed for the in-s itu investigation of non-equilibrium solidification phenomena in under cooled melts are discussed, and their potential for such investigation s is evaluated. Aspects of microgravity research in this field are als o included.