The synergistic effects of heterogeneous structures enhance the strength-ductility of Al-Cu composites

The microstructural design offers an effective strategy for overcoming the strength-ductility trade-off in Al-based composites. In this study, we demonstrate concurrent improvements in strength and ductility of Al-Cu composites by introducing heterogeneous structures, including low-angle grain boundaries (LAGBs), stacking faults (SFs), and nano-CuAl2. A high density of LAGBs refines Al grains by absorbing dislocation into high-angle grain boundaries (HAGBs) during deformation, which helps to suppress crack propagation under plastic deformation. The absorption of dislocations by LAGBs prevents dislocation pile-up at grain boundaries, thereby reducing stress concentration. The stacking fault network formed at the heterogeneous interface between Al and CuAl2 effectively reduces the mean free path of dislocation motion, overcoming the Hall-Petch limit in microcrystalline grains. Nano-particles further contribute to Orowan strengthening by hindering dislocation motion. The synergistic effect of these heterogeneous structures successfully evades the strength-ductility trade-off in Al-Cu composites, providing an efficient strategy by multiscale defects to facilitate maintaining plasticity in metal- matrix composites. Employing multiscale defects provides an efficient strategy to maintain plasticity in metal- matrix composites.