Effects of Cu on microstructure and mechanical properties of sand casting Al-Si-Cu-Ni alloy were analyzed by tensile testing

hardness testing and OM （optical microscope） and energy spectrum analysis. It is found that with increasing in Cu content

Al-Ni-Cu phase and CuAl2 phase in the alloy are increased

which results in the improvement of tensile strength of the alloy at room temperature and at 250℃ and decrease of elongation of the alloy.