Effect of G-phase and heterogeneous deformation-induced strengthening on the mechanical properties of Cu-20Ni-20Mn-2Fe-1Si alloy

Abstract

It is a challenge to simultaneously improve the strength and plasticity of ultra-high strength and high elasticity copper alloys. A synergistic strengthening strategy of heterogeneous deformation-induced strengthening (HDI) and grain refinement strengthening is proposed. Cu-20Ni-20Mn-2Fe-1Si has been designed according to this strategy. The addition of Si formed G-phases (Mn6Ni16Si7) in the alloy, which have an average size of 1 μm and a volume percentage of about 9.36%. There is a significant hardness difference between the Cu-rich phases and the G-phases, and the large strain gradient during deformation leads to HDI strengthening. After 75% cold rolling, solid solution at 830 °C for 2 h, and aging at 450 °C for 88 h, a large amount of NiMn phases of about 4–8 nm precipitated in the alloy and the average grain size is about 2.8 μm. The tensile strength, yield strength, elastic modulus, and elongation of the alloy reached 1.37 GPa, 1.27 GPa, 149.4 GPa, and 6.04%, respectively. The calculation results show that precipitation strengthening, HDI strengthening, grain refinement strengthening, solid solution strengthening contribute 0.63 GPa, 0.45 GPa, 0.08 GPa, and 0.08 GPa to the total strength, respectively. All of these provide new ideas for the design of novel ultra-high strength and high elasticity copper alloys.