UNDERCOOLING AND SOLIDIFICATION OF DROPLETS OF CU-AG ALLOY ENTRAINED IN THE PRIMARY PHASE

The undercooling behaviour and formation of metastable microstructures have been studied in the melt of Cu-Ag alloy entrained in its primary phase. A maximum undercooling of 180 degrees C below the liquidus tem perature was observed in isolated liquid droplets. The highly undercoo led droplets underwent a massive transformation which resulted in the formation of a metastable solid-solution phase containing Ag-28 at % C u. The metastable phase decomposed on ageing to form the equilibrium p hases. The undercooling behaviour and evolution of metastable microstr uctures in droplets are discussed.