Strain-rate sensitivity, activation volume and mobile dislocations exhaustion rate in nanocrystalline Cu–11.1 at%Al alloy with low stacking fault energy

The strain rate sensitivity, activation volume and exhaustion of mobile dislocation density in nanocrystalline (NC) Cu–11.1 at%Al alloy with low stacking fault energy were studied by strain rate jump tests and repeated stress relaxations at room temperature. It was found that in comparison with NC Cu with similar grain size, the strain rate sensitivity of NC Cu–Al alloys is much small, which might due to the low SFE and the tendency of chemical short range order formation during plastic deformation. The small physical activation volume (~20b3) was determined, which could be ascribed to the dislocation processes mediated by grain boundaries, twin boundaries. Meanwhile, a lower exhaustion rate of mobile dislocation density was found, possibly due to the low stacking fault energy enhancing dislocation storage capability, the high densities of nanotwins preserving mobile dislocations and a lower dislocation velocity in concentrated alloys.