Simultaneously enhanced strength and ductility of Cu-xGe alloys through manipulating the stacking fault energy (SFE)

Vinogradov et al. [1] reported that the stacking fault energy (SFE) of Cu-xGe alloys with germanium concentration varying from 0, 0.1, 5.7 to 9.0 at% alters from 78, 54, 15 to 8 mJ/m2, respectively. In the present study, the Cu-xGe alloys were prepared by forging at the liquid nitrogen temperature and their mechanical properties were systematically investigated. Results indicated that the microhardness, strength and uniform elongation of Cu-xGe alloys were simultaneously improved by lowering the SFE. X-ray diffraction measurements revealed that a reduction in SFE leads both to a decrease in grain size and an increase in dislocation density, twin density and microstrain for the cryogenic forged samples and these contribute to the improvements in the mechanical properties. This work demonstrates that high strength and excellent ductility can be simultaneously achieved by lowering SFE of the metals.