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.