The influence of strain rate, deformation temperature and stacking fault energy on the mechanical properties of Cu alloys

Cu-Ge alloys with different stacking fault energies (SFEs) were prepared by induction melting and processed by severe plastic deformation (SPD) using three different deformation techniques, including rolling at room temperature (RTR), rolling at the liquid nitrogen temperature (LNR), and Split Hopkinson Pressure Bar (SHPB) impact followed by room temperature rolling (HK+RTR). The effects of SFE, strain rate and deformation temperature on the microstructures and mechanical properties were systematically investigated by X-ray diffraction analyses and tensile tests. It was found that the dislocation density and twin density of all the Cu alloys after the SPD processing increased with decreasing SFE, increasing strain rate or reducing deformation temperature, which led to simultaneously enhanced strength and improved ductility due to effective grain refinement. The mechanical properties of the Cu alloys can be optimized to a combination of high strength and excellent ductility by lowering the SFE, the intrinsic property of metals, or manipulating the extrinsic deformation conditions, that is, increasing strain rate, and/or decreasing deformation temperature.