Undercooling and demixing in rapidly solidified Cu–Co alloys

The Cu–Co system displays a metastable miscibility gap in the liquid state. A considerable amount of work has been performed to study phase separation and related microstructures showing that demixing of the liquid is followed by coagulation before dendritic solidification. Due to kinetic competition of transformation phenomena, the mechanisms have not been fully disclosed.This contribution reviews such findings with the help of a computer calculation of the phase diagram and extends the present knowledge by presenting new results obtained by rapidly solidifying various Cu–Co compositions using a wide range of cooling rates achieved by forcing the liquid into cylindric and conic moulds and by melt spinning.