Effect of Ni and Si additions on the microstructure and mechanical properties of Cu-7Sn alloy

On the basis of the traditional solid solution strengthened Cu-7Sn alloy, the alloy phase diagram and thermodynamic calculation, combined with the first nature principle results for the design of the alloy composition and heat treatment regime, the physical phase composition of the alloy under different temperature conditions was investigated and experimentally characterized. By analyzing the phase compositions of the alloys with different compositions and temperatures, a new precipitation-strengthened Cu-7Sn-1Ni-0.4Si alloy was designed and prepared. The results show that the Cu-7Sn-1Ni-0.4Si alloy prepared by the melt casting method with Ni and Si elements as alloying elements according to the phase diagrams and first principle calculations can successfully introduce the δ-Ni₂Si precipitation phase into the alloy after the solution treatment at 850 ℃ for 3 h and the aging treatment at 400 ℃ for 5 h, which can significantly enhance the mechanical properties of the alloy. The Vickers hardness, tensile strength and elongation of the alloy can reach 160.7 HV, 550 MPa and 18%, respectively.