Semi-solid Al-6Si-2Mg alloy billets with fine spherical grains were prepared by self-developed vibrating wave-like sloping plate device

and effects of different reheating processes on microstructure of the billets were observed. The results reveal that solute diffusion is accelerated

and liquid region near grain boundary tends to be continuous and liquid fraction rises with increasing in holding temperature at a given holding time. Due to the role of interface free energy

average grain size exhibits firstly increase and then decrease

meanwhile

average grain roundness and density show gradually decrease. At a given holding temperature

with extending in holding time

eutectic liquid phase is increasingly raised to be formed a continuous liquid network to separate the grain. To decrease interface free energy

grain size exhibits firstly increase and then decrease

while grain roundness is decreased with raising in liquid fraction. Desirable semi-solid slurry with spherical grain suspending on liquid phase can be obtained with holing at 610 ℃ for 60 min.