A new synergy to overcome the strength-ductility trade-off dilemma in Al–Si–Cu alloy by micro-nano-particle complex clusters

The effects of the novel micro-nano-particle clusters (nano-AlN and submicron-TiC particles doped with B, referred as TiC_B) on the microstructure and mechanical properties of the Al–9Si–3Cu alloy are investigated herein. Comprehensive analysis revealed that the nano-AlN particles resulted in a significant modification of eutectic Si by causing the poisoning of twin plane re-entrant edge growth of Si and restricting the growth of Si crystals. Correspondingly, the morphology of Si transformed from flaky to fibrous. Furthermore, the synergy of areas with and without particle clusters was emphasized to address their contributions to the simultaneous improvement of the strength and ductility. When inoculating the micro-nano-particle clusters into the Al–9Si–3Cu alloy, the yield strength, ultimate tensile strength, and elongation were 138 MPa, 253 MPa, and 5.8%, respectively, corresponding to increases of 23.2%, 23.4%, and 123.1% compared with those of the uninoculated Al–9Si–3Cu base alloy (112 MPa, 205 MPa, and 2.6%, respectively). After T6 heat treatment, the spheroidal Si and θ′ phases on the Al matrix further improved the strength of the Al–9Si–3Cu alloy. This work may provide a promising strategy to design and fabricate Al–Si–Cu alloy with high strength and ductility.