Microstructures and properties of Ni-Si precipitation strengthened phosphor bronze

Abstract

To strengthen phosphor bronze, this work attempted to form precipitate nanoparticles in the matrix by adding alloying elements. First, Ni and Si were identified as alloying elements through mixing enthalpy analysis. Then, Cu-8Sn-0.1P, Cu-8Sn-0.1P-0.5Ni-0.12Si, Cu-8Sn-0.1P-1Ni-0.24Si, and Cu-8Sn-0.1P-2Ni-0.48Si alloys were prepared by intermediate frequency induction furnace. After that, the microstructures of these alloys were characterized and their properties were tested. Experimental results indicated that Ni31Si12, Ni2Si, and Ni5P4 phases are newly formed in the as-cast microstructure after adding Ni and Si. At the same time, the eutectoid size of α-Cu and Cu41Sn11 in the as-cast microstructure of Ni-Si added phosphor bronze is reduced, the secondary dendrite arm spacing is reduced, and the segregation is also improved. After aging treatment, nano-sized cellular Ni2Si and trace Ni5P4 phases are precipitated in the Ni-Si added phosphor bronze. With the formation of nanoprecipitates, Ni-Si added phosphor bronzes show excellent precipitation strengthening effect after aging treatment, and the electrical conductivity of Cu-8Sn-0.1P-0.5Ni-0.12Si and Cu-8Sn-0.1P-1Ni-0.24Si alloys is also slightly higher than that of Cu-8Sn-0.1P. This study provides a new solution for strengthening phosphor bronze, enabling phosphor bronze alloys to meet higher performance and broader applications.