Synergistic improvement of ultra-high strength and ductility of Cu-15Ni-8Sn alloy induced by multi-pass rotary swaging and aging treatment

The Cu-15Ni-8Sn alloy can achieve ultra-high strength through heat treatment processes, but the significant reduction in its ductility limits its wider applications. How to synergistically enhance the strength and ductility of this alloy is a hot research topic. In this study, the industrial Cu-15Ni-8Sn alloy was taken as the research object, and the changes in alloy grain characteristics and mechanical properties under different cumulative deformations were compared by multi-pass rotary swaging deformation of the solution-state Cu-15Ni-8Sn alloy followed by aging heat treatment with different holding times. The evolution of phase structures in the rotary-swaged Cu15Ni-8Sn alloy during the aging process was investigated. The synergy mechanism of rotary swaging and aging process on the strength and ductility of the alloy was revealed. The results showed that with the increase of rotary swaging deformation, the Cu-15Ni-8Sn alloy grains gradually elongates until they tended to be fibrous, and the grain texture changed from random distribution to <111> and <100> distribution. Rotary swaging deformation promotes the precipitation of the D022 ordered phase. After 75 % rotary swaging deformation and aging treatment at 400 degrees C for 60 min, the ultimate tensile strength and elongation of the Cu-15Ni-8Sn alloy reaches 1405 MPa and 6.1 %, respectively. The characteristics of high strain rate and large cumulative deformation of rotary swaging activate more slip systems and twin systems, improve the strengthening efficiency, and are conducive to uniform deformation and plasticity of metals. Rotary swaging deformation promotes the formation of D022 ordered phase during aging, and the interaction between nanoscale precipitates and dislocations produces a significant precipitation strengthening effect. Based on the above synergistic effects, the results of this paper realize the simultaneous improvement of strength and plasticity of Cu-15Ni-8Sn alloy. This optimization of comprehensive mechanical properties makes the alloy very suitable for use in complex environments requiring high strength and good machining capability.