The effect of Zr element on the microstructure and properties of Cu–Ni–Si alloys

In order to investigate the effect of Zr addition on Cu–Ni–Si alloys, this study developed four Cu–Ni–Si-(Zr) alloys with different Zr contents based on the Cu-3.2Ni-0.7Si alloy and systematically analyzed their microstructure and property variations. After undergoing the same deformation and heat treatment processes, it was found that, in addition to Ni 2 Si, the alloy also formed the intermetallic compound Ni 16 Zr 6 Si 7 . As the Zr content increased, the activation energy for Ni 2 Si precipitation gradually decreased, leading to an increased precipitation rate. Meanwhile, the particle size and content of Ni 16 Zr 6 Si 7 also increased. During hot rolling, Ni 16 Zr 6 Si 7 promotes the nucleation Cu grain recrystallization and pins the grain boundaries, leading to a gradual reduction in grain size. This reduction in grain size contributes to improved plasticity and toughness of the alloy. However, due to the relatively large particle size, the formation of Ni 16 Zr 6 Si 7 has a smaller strengthening effect on the alloy. The increase in alloy strength primarily relies on the precipitation strengthening provided by the nano-sized Ni 2 Si formed during heat treatment. Therefore, when the Zr content is 0.05 wt%, the strengthening effect of Ni 2 Si is significantly improved compared to the Cu-3.2Ni-0.7Si alloy, while the precipitation of Ni 16 Zr 6 Si 7 particles remains relatively low, resulting in the best overall performance of the alloy. After aging at 450 °C for 6h, the peak hardness of Cu-3.2Ni-0.7Si-0.05Zr reaches 270.1HV, with conductivity of 37 %IACS, tensile strength of 692.5 MPa, and elongation of 10.1 %.