Fabrication of Cu–Ni–Si alloy by melt spinning and its mechanical and electrical properties

Abstract

Cu alloys with compositions of Cu-3.2Ni-0.7Si (wt. %) and Cu-2.8Ni-0.7Si (wt. %) were prepared by melt spinning. Effects of composition, spinning rate, aging temperature and time on microstructure, precipitation of reinforcing phases, mechanical and electrical properties of Cu–Ni–Si alloys were investigated. Melt spinning could produce continuous Cu alloy ribbons with thickness and width of the ribbons mainly dependent on the cooling rate. Columnar grains of super-saturated Cu–Ni–Si solid solutions grew in the ribbons. The melt-spun Cu–Ni–Si alloys had a faster aging kinetics in comparison with commercial alloys of similar compositions. Peak-aging of the melt spun alloys appeared after heating at 400 to 550 °C for 1 to 2 h to show maximum tensile strength of 650 to 700 MPa. Prolonged heating resulted in large precipitates on the grain boundaries and formation of precipitation-free zones around each grain with sharp drop of tensile strength. Precipitation of nano δ-Ni2Si rather than other phases was the main reason for the enhanced mechanical properties at peak-aging. The peak- and slightly over-aged ribbons had a good electric conductivity up to 55% IACS.