Grain refinement in solidification of highly undercooled eutectic Ni–Si alloy

Substantial undercooling up to 550 K (0.386TE, with TE as the melting point) was achieved in eutectic Ni78.6Si21.4 alloy melt using glass fluxing combined with cyclic superheating. Accordingly, a particular refined microcrystalline morphology is obtained in the as-solidified structure. The physical mechanism of the grain refinement subjected to high undercooling is interpreted in terms of the classical nucleation theory and LKT/BCT model. It was concluded that the above refinement can be ascribed to the substantially increased nucleation rate under high undercooling.