The influence of zirconium addition on microstructure evolution, precipitation behavior, and properties of Cu-Ni-Ti alloy

This study systematically investigated the effects of a small amount of Zr addition on the microstructure evolution, mechanical, and electrical properties of Cu-Ni-Ti alloy, specifically focusing on Cu-3Ni-1Ti- (0.3Zr). The results indicate that adding an appropriate amount of Zr significantly enhances the mechanical properties and over-aging resistance of the Cu-Ni-Ti alloy, with only a slight decrease in conductivity. After aging at 500 degrees C for 2 h, Cu-3Ni-1Ti-0.3Zr exhibits an ultimate tensile strength of 673 MPa and a conductivity of 53 % IACS. Even after extending the aging time to 10 h, the tensile strength and conductivity remain high at 646 MPa and 61 % IACS, respectively. Microscopic analysis reveals that the addition of Zr promotes the formation of fine Ni3Ti phase during solidification and solution treatment, improving the deformation resistance and enhances its yield strength of the alloy in the cold-rolled state. Additionally, it hinders the migration of grain boundaries,suppressing the recovery and recrystallization processes, thus maintaining high mechanical properties and over- aging resistance. Furthermore, the precipitation of coherent or semi-coherent nano Ni3Ti phases during the aging process positively affects the alloy's yield strength and conductivity. The Oworan and dislocation strengthening mechanisms resulting from nano Ni3Ti phases are the primary mechanisms enhancing the yield strength of Cu-3Ni-1Ti-0.3Zr alloy, contributing approximately 87 %.