Microstructure and Strengthening Mechanism of Hot-Extruded Cu-17Ni-2.5Sn-1.5Al Alloy

Homogenization annealing treatment at 930℃ for 2.5 h and hot extrusion at 950℃ were conducted on as-cast Cu-17Ni-2.5Sn-1.5Al alloy in sequence. The microstructure and tensile properties of the hot-extruded alloy were studied, and the strengthening mechanism was analyzed. The results show that the microstructure of the hot-extruded alloy was refined obviously to average grain size of about 32 μm. Spherical Ni₃Al phase with a diameter of about 10 nm dispersed in the matrix structure. The ultimate tensile strength of the hot-extruded alloy was 922 MPa and the yield strength was 779 MPa. The alloy had three types of strengthening mechanism, namely refinement crystal strengthening, solid solution strengthening and second phase precipitation strengthening. The solid solution strengthening played a main role and accounted for 56% of the total strengthening effect. Aluminum played a solid solution strengthening role and a second phase precipitation strengthening role.