The effects of Al-4P modification on microstructure and machinability of hypereutectic Al-20 Si alloy were investigated by orthogonal experiment

and the process parameters of improving hypereutectic Al-20 Si alloy machinability were optimized. The results show that the added amount of Al-4P is the most significant impact on the primary silicon

then the modification time

modification temperature. The optimized process parameters of improving the Al-20 Si alloy machinability were presented as follows: the addition of Al-4P of 1% at 760 ℃ for 1h. After modification treatment

the primary silicon becomes small with dispersed and round passivation

and the average size is reduce from 120 μm to 30 μm

so the tool life is increased and the machinability is improved.