Sb and RE mixed modification on Al-7Si-0.3Mg alloy has been performed. It is found that Sb and RE mixed modification can greatly refine the eutectic phase in the alloy

in which the twinned or fibrous Si phase can appear with the RE addition. Differential thermal analysis indicates that compared with that in the untreated alloy

the precipitated temperature of eutectic Si phase from the alloy treated by Sb or RE or SB plus RE mixed modification is obviously declined. The precipitated temperature of eutectic Si phase in the alloy modified by 0.15% RE is decreased by 7 ℃ with cooling at 50 ℃/min

that modified by 0.15% Sb is decreased by 5 ℃

and that modified by 0.15% Sb plus 0.15% RE is nearby to that by 0.15% Sb modification. The Sb plus RE mixed modification effect is superior to that of Sb or RE only

which is attributed to Sb promoting the nucleation and refinement of eutectic Si phase and RE resulting in the generation of twinned and fibrous eutectic Si phase. The mechanical properties of the alloy modified by Sb plus RE are greatly improved

especially the elongation.