Effects of P modification

P-Sb compound modification and Mg content on microstructure of Al-Si alloy were investigated.The results show that the size of primary Si is decreased from 40μm to 20μm and the length of eutectic Si is decreased from 20μm to 12μm with more uniform distribution after P modification

so both tensile strength and yield strength of the P modified alloy are increased approximately 15%.The size of primary Si is decreased to 5μm

and dendrite size ofα-Al is obviously refined after P-Sb compound modification

meanwhile

the shape of eutectic Si appears wormlike

so tensile strength and yield strength of the alloy are increased about 8% compared with those of the alloy with P modification.With the increase of Mg content

the Sb modification effect is promoted

where the shape of eutectic Si appears with absence of primary Si and refinement of dendrite size ofα-Al

so tensile strength and yield strength of the alloy are increased about 3% compared with those of ones with P-Sb modification.