The effects of Sb additions on the microstructure and tensile properties of A356 alloy were investigated systematically

and thermal analysis and quenching experiments were carried out to explore the modification mechanism of Sb on Al-Si alloys.Microstructure observations show that with 0.4% Sb addition

coarse plate-like eutectic silicon phase can be converted into fibrous structure.Tensile tests show that the mechanical properties（especially the elongation）of A356 alloys are improved greatly.The maximum elongation value reaches 11.3% under as-cast condition

which is 79% higher than that of the unmodified alloy.Thermal analysis and quenching structure observation reveal that the nucleation temperature of eutectic Si phase is continuously decreased with Sb additions

therefore the nucleation undercooling can be increased to decrease nucleation rate of eutectic Si phase.