DENUCLEATION AND HIGH UNDERCOOLING OF Ni-32.5%Sn EUTECTIC ALLOY

Undercoolings up to 397 K(0.283 T_E)have been obtained for Ni-32.5% Sn eutectic alloy melted by superheating-cooling cycles and denucleating with inorganic glasses.The predomi- nant dissipation of heat for highly undercooled alloy melt is through radiation.An approxi- mate method is consequently derived to calculate its mean specific heat from measured cooling curves.With the aid of high speed cinematography,it is revealed that the surface or interface heterogeneous nucleation takes place in preference to homogeneous nucleation even though the undercooling has exceeded 0.2 T_E.