Competitions Correlated with Nucleation in Non-equilibrium Solidification of Bulk Undercooled Alloy Melt

Nucleation plays a key role in solidification processing.The present overview focuses on a series of competitions incorporated in nucleation upon non-equilibrium solidification of bulk undercooled alloy melt.According to the classical nucleation theory and the newly developments in nucleation field,three nucleation modes,namely,continuous nucleation,site saturation and free growth are proposed for different solidification conditions.Competition of nucleation modes,which consists of continuous nucleation and athermal nucleation(site saturation and free growth),competition between one point and copious nucleation,competition between homogeneous and heterogeneous nucleation,were separately discussed in various alloy systems.At the same time,experiment evidences were given and analyzed to prove these competitions.Additionally,some criterions for determining nucleation mechanism were also proposed.