Abstract:The microstructure of semisolid metal comprises nondendritic solid phase grains suspended in liquid matrix, which is the key technological foundation for semisolid processing. In this paper, the formation mechanism for nondendritic structure in semisolid metal is proposed, namely mechanism of particledrift and blendingcompressing. Under vigorous convection caused by intense electromagnetic stirring, the dynamic solidification process of melt is quite different from that of conventional casting which is relatively static. The transferring of heat and mass during solidification is greatly changed by vigorous convection,and determined the microstructure. Particledrift greatly increases the heterogeneous nucleation and so refines the grains; Blendingcompressing changes the growing morphology of primary grains and makes grains grow relatively uniformly in all directions into near globular shape, and results in nondendritic structure.

Key words: semisolid processing； nondendritic structure； electromagnetic stirring