Microstructure and Properties of a Novel Cu–Ni–Co–Si–Mg Alloy with Super-high Strength and Conductivity

Abstract

The Cu–4.5Ni–1.2Co–1.0Si–0.15Mg alloy with super-high strength and high electrical conductivity was designed, and a two-step thermo-mechanical treatment was applied to improve the mechanical and electrical properties of the alloy. The microstructure and properties of the alloy were investigated by transmission electron microscope observation, tensile test, hardness and electrical conductivity measurements. The results show that the final alloy treated by two-step thermo-mechanical process has a hardness of 329 HV, a yield strength of 1086 MPa, an elongation of 3.6%, and an electrical conductivity of 30.1%IACS, respectively. The nanoscale β-Ni3Si and δ-(Co,Ni)2Si precipitates form during the thermo-mechanical process, and the addition of the Co could promote the precipitation of δ-(Co,Ni)2Si particles. The orientation relationship (OR) between Cu matrix and the precipitates is: (022)Cu//(011)β//(010)δ and [100]Cu//[100]β//[001]δ. Comparing with the directly aging treatment and one step thermo-mechanical treatment, precipitates that form during the two-step thermo-mechanical process are much smaller and distributed more densely, resulting in the better comprehensive properties of the alloy.