High strength and high electrical conductivity C70250 copper alloy with fibrous structure reinforced by high density, multi-scale nano-precipitates and dislocation

Abstract

Cu–Ni–Si alloy has a difficult combination of high strength and high electrical conductivity, which limits its further application in electronics industry. In this work, the effects of large deformation double cold rolling-aging processes on the microstructure, mechanical properties and electrical conductivity of the columnar grain alloy were studied, and its mechanism was revealed. The results show that the C70250 copper alloy strip prepared by hot mold continuous casting technology can be directly subjected to large deformation double cold rolling-aging treatments without solid solution process. The excellent balance of tensile strength and electrical conductivity, as high as 884 MPa and 45.7% IACS, respectively, can be obtained for the alloy after primary 95% cold rolling and aging at 450 °C for 45 min followed by secondary 60% cold rolling and aging at 400 °C for 10 min. The strength and electrical conductivity is better than the similar products reported. The realization of high strength and high electrical conductivity is attributed to the interaction between strain hardening and precipitation behavior of columnar alloy during double deformation and aging treatment. The repeated introduction of large deformation cold rolling provides a new short diffusion driving force for the precipitation of solute atoms by GPA and APT results, the precipitation rate is increased in the second stage of aging. At the same time, the nanometer-sized strengthening phase formed by primary aging can effectively nail the dislocations formed in the secondary cold rolling process, and finally form a fibrous structure with uniform mixing of multi-scale nano cluster and Ni2Si phase. The strength of the alloy is significantly improved by dislocation strengthening and multi-scale precipitation strengthening. C70250 copper alloy precipitate as many solute atoms as possible, and retains fibrous structure, the dispersing of electrons by solute particles and grain boundary limits is fundamentally diminished, and the electrical conductivity is improved.