Achieving high strength and high elasticity of Cu–Ni–Cr–Mn alloy by synergistic effect of multi-scale precipitates

Abstract

The microstructural evolution, precipitation behavior and mechanical properties of Cu–19Ni–6Cr-xMn (x=0, 1, 3, 5, 7, 9 wt%) alloys were examined in the presence of solution treatment, cold rolled treatment and aged treatment. The results show that aged Cu–19Ni–6Cr–7Mn alloy exhibits superior mechanical properties with a hardness of 379 HV, tensile strength of 1012 MPa, and elastic modulus of 149.5 GPa, which is the maximum reported value for elastic modulus of copper alloys. The Mn element promotes the uniform distribution of the precipitates and grain refinement. Thermodynamic calculations indicate that the formation of the NiMn precipitates takes precedence over the NiCr-rich precipitates in this alloy. Three typical precipitates were detected in the Cu–19Ni–6Cr–7Mn alloy, including submicron-sized Cr-rich precipitates (>500 nm), nano-sized bcc-Cr precipitates (30–70 nm), and nano-sized NiMn precipitates with L12 ordered structure (3–5 nm). Precipitation plays a major role in improving the strength of the alloy. The synergistic effect between multi-scale precipitates, high-density dislocations, and solution strengthening has achieved significant breakthroughs in mechanical properties which open up new possibilities for engineering applications requiring high-strength and high-elasticity copper alloys.