Effects of cold deformation and aging on the phase transformation and mechanical properties of a Cu-15Ni-8Sn alloy

Abstract

A Cu-15Ni-8Sn alloy ingot was prepared in a medium-frequency induction melting furnace. First, the hot extruded alloy was subjected to solution treatment at 840 °C for 60 min, after which cold drawing treatment was applied under different deformation conditions (0–70%). Finally, the cold-deformed alloy was subjected to aging at different temperatures (340–520 °C) and insulation times (0–480 min). The evolution of grain characteristics, micromorphology and mechanical properties during cold drawing deformation and aging were systematically studied. The results show that during cold drawing deformation, the grains in the solid solution Cu-15Ni-8Sn alloy gradually elongate along the drawing direction with increasing deformation, and the texture changes from a discrete distribution to a hard orientation. Cold drawing deformation promoted coarsening of the modulated structure and the transition of the D022 ordered phase. Dislocations and twins increased the occurrence of nucleation for the discontinuous precipitates and promoted the growth of the discontinuous precipitates, but cold deformation inhibited the transition of the D022 ordered phase to the L12 ordered phase. The hardness, tensile strength and elongation of the Cu-15Ni-8Sn alloy after 50% cold deformation were 109.2 HRB, 1258.3 MPa and 7.5%, respectively, after aging at 400 °C for 60 min. The main strengthening mechanisms of the peak-aged alloy were precipitation strengthening and dislocation strengthening.