There exists an obvious difference in solidification characteristics of the alloy melt between by weak electromagnetic stirring with low super-heating pouring and by conventional casting.It is important to understand deeply the microstructure evolution of the alloy by analyzing the grain nucleation and growth of the stirred alloy based on solidification theory.The solidification process of semi-solid Al-30Si alloy was described by analyzing effects of weak electromagnetic stirring with low super-heating pouring on the moving of melt and nucleation.The results reveal that the tangential velocity of liquid melt is dominant in stirring process

and the radial and axial velocity can be neglected.The low super-heating pouring can directly increase the nucleation rate in semi-solid alloy and the weak electromagnetic stirring can indirectly increase the nucleation rate.