Effects of thermal plastic deformation on microstructure and mechanical properties of eutectic Al-Si alloy have been investigated. The results show that tensile strength of as-cast alloy after thermal plastic deformation can be improved from 205 MPa to 260 MPa and its elongation can be increased from 3. 2% to 10%

which is attribute to spheroidize eutectic Si particle and solder shrinkage hole and shrinkage porosity. Moreover

tensile strength of the alloy can be increased from 292 MPa to 397. 4 MPa

and elongation can be raised from 0. 5% to 6. 5% after heat treatment.