Decoupling effect stimulated independent dendrite growth of eutectic phases under microgravity and containerless states

Abstract

Eutectic growth process is usually characterized by the simultaneous coupled growth of two different solids within one uniform liquid phase, while fluid dynamics normally predicts the equiaxed shrinkage for floating viscous droplets on freezing. Here a decoupling effect was induced by the microgravity and containerless states aboard space station, which led to the independent dendrite growth of two eutectic phases within extremely undercooled liquid Nb-Si refractory alloy. The confronting fluid flow pattern driven by polar heterogeneous nucleation was found to stimulate the elongated surface deformation of alloy droplet at a high dendrite growth velocity.