Effects of Nd and Cu on Microstructure and Mechanical Properties of Hypereutectic Al-20Si Alloy

In this paper, the modification of Nd to hypereutectic Al-20Si alloy was studied, and the effects of Cu on the microstructures and mechanical properties of the modified Al-20Si alloy were investigated. The results showed that the primary Si transformed from irregular morphology to fine polyhedral morphology, and the morphology of eutectic Si transformed from acicular/lamellar to short-rod and point like after modification. Compared with Al-20Si alloy, the tensile strength of Al-20Si-0.3Nd increased by 22.8%, and the elongation increased by 127.8%. The strengthening phase CuAl2 appeared in the Cu-containing Al-20Si-0.3Nd alloy; as a result, the mechanical properties of Al-20Si-0.3Nd-Cu alloy were improved. Compared with Al-20Si alloy, the tensile strength of Al-20Si-0.3Nd-2.0Cu alloy increases by 39.5%, and the elongation doesn't decrease.