Enhanced softening resistance and mechanical properties of Cu-Ni-Sn alloy with Al, Zn and Si micro-alloying

Microalloying is an effective method for enhancing the mechanical properties and softening resistance of alloys. The effects of microalloying with Al, Zn, and Si on the microstructure, physical properties, and softening resistance of Cu-Ni-Sn alloy were investigated. The results showed that the micro-alloying of Al, Zn, and Si suppressed the segregation of the Cu-Ni-Sn alloy. After 70% cold rolling and 400 °C aging, the Cu-15Ni-5.5Sn-1.5Al-0.5Zn-0.5Si alloy reaches its maximum hardness of 418 HV, which is 16 HV and 38 HV higher than that of Cu-15Ni-8Sn and Cu-15Ni-5.5Sn alloys, respectively. Furthermore, Al, Zn, and Si microalloying can increase the softening temperature of Cu-Ni-Sn alloy. Cu-15Ni-5.5Sn-1.5Al-0.5Zn-0.5Si alloy's softening temperature was 560 °C, which was higher than Cu-15Ni-8Sn (400 °C) and Cu-15Ni-5.5Sn (420 °C) alloys. The softening of the alloy is mainly caused by the rapid formation of discontinuous precipitates and the reduction of dislocation density. The Al and Zn solute atoms dissolved in the matrix and the micron-scale Ni31Si12 phase forms can effectively inhibit discontinuous precipitation formation and dislocation movement during the aging and annealing process, resulting in excellent mechanical properties and softening resistance of the Cu-15Ni-5.5Sn-1.5Al-0.5Zn-0.5Si alloy. In further works, continued efforts are needed in the multi-component design of Cu-Ni-Sn-x alloy to optimize its comprehensive performance.