Anomalous recovery of work hardening rate in Cu-Mn alloys with high stacking fault energies under uniaxial compression

The work hardening behavior and deformation microstructures of pure Cu and Cu-Mn alloys were systemically investigated under uniaxial compression. An anomalous phenomenon of work hardening rate recovery was observed in the present Cu-Mn alloys with high stacking fault energies (SFEs). Such a phenomenon is dramatically distinctive from those observed in previous studies on high-SFE metals, whose work hardening rate monotonically decreases with the increase of strain. Microstructural examinations demonstrate that the occurrence of work hardening rate recovery should be attributed to the transformation from wavy slip to planar slip by increasing Mn content, since these planar slip dislocation structures effectively inhibit dynamic recovery and reduce the dislocation mean free path. Therefore, the possible influencing parameters such as SFE, friction stress, and short-range ordering (SRO) are analyzed. It is suggested that the existence of SRO in Cu-Mn alloys is the main reason causing planar slip. Furthermore, the effect of SRO on the multi-stage work hardening behavior is discussed based on the analyses of dislocation density evolution during deformation. This study enriches a fundamental knowledge of how to improve the work hardening capacity of alloys with high SFEs.