Effects of stacking fault energy, strain rate and temperature on microstructure and strength of nanostructured Cu–Al alloys subjected to plastic deformation

Abstract

Nanostructured Cu–Al alloys with different stacking fault energies (SFEs) corresponding to Al concentrations in a range of 0–4.5 wt.% are prepared by means of plastic deformation. Effects of SFE, strain rate and temperature on microstructure characteristics and strength have been systematically investigated in the Cu–Al alloys. It was found that the deformation occurs mainly by twinning at the nanoscale in all samples subjected to dynamic plastic deformation at liquid nitrogen temperature. In the quasi-static compression process at room temperature, dislocation slip dominates the plastic deformation when the SFE is higher than 50 mJ m −2. With decreasing SFE, twinning becomes the dominant deformation mechanism. A map of deformation modes and corresponding strain-induced microstructures is drawn in the SFE-processing parameters space for the Cu–Al alloys. In both sets of deformation mode, twinning is obviously enhanced by decreasing the SFE, resulting in smaller twin/matrix (T/M) lamella thickness and grain sizes. Consequently, an obvious strength elevation is induced by the size effects of grains and T/M lamellae with lower SFEs.