The comprehensive performance and strengthening mechanism of the columnar crystal Cu-Ni-Si alloy after two large deformation rates of cryogenic rolling-aging

In order to improve the strength and electrical conductivity of Cu-Ni-Si alloy, the columnar crystalline C70250 copper alloy strip suffer from two deep cryogenic rolling-aging treatments with large deformation, and the relationship between the cryogenic rolling-aging process and microscopic structure, mechanical, conductive properties is studied, and the precipitation behavior is analyzed. The research findings show that the columnar crystalline C70250 copper alloy produced by continuous directional solidification can be directly processed by two cryogenic rolling-aging treatment with large deformation, eliminating the traditional solution treatment process and obtaining a fibrous tissue structures containing high-density dislocations and multi-scale precipitates, the yield strength, tensile strength and electrical conductivity of the alloy reached 879 MPa, 923 MPa and 38.7 % IACS respectively, combination of strength and electrical conductivity is excellent. Two deep cryogenic rolling with large deformation can force the matrix to change to amorphous, favorable to atomic diffusion. Solute atoms are continuously transformed into Ni2Si phase and Cu atoms are continuously expelled, forming large-sized pure Ni2Si precipitated phase and small-sized NiSi cluster phase containing Cu atoms, which together impede dislocation movement and reinforce alloy. With the uniform precipitation of multi-scale nano-precipitation phases and reduction of grain boundary density, the electrical conductivity along the rolling direction is significantly reduced.