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

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 degrees 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 delta-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.