Breaking the strength-ductility trade-off in additively manufactured aluminum alloys through grain structure control by duplex nucleation

Achieving a homogeneous equiaxed grain structure and breaking the strength-ductility trade-off in additively manufactured aluminum alloys is a great challenge. In this paper, we propose a novel duplex nucleation mechanism that combines ex situ TiB₂ and in situ Al₃Ti for controlling the grain structure of additively manufactured AlCuMgTi-TiB₂ composites. We conducted thermodynamic calculations and phase-field simulations to elucidate the duplex nucleation-based grain structure control. The Al₃Ti-coated TiB₂ inoculant system formed via duplex nucleation during solidification enabled the formation of a ho-mogeneous ultrafine equiaxed microstructure in both the as-fabricated and heat-treated states. Different from the AlCuMgTi alloy, the TiB₂-reinforced AlCuMgTi composites produced via laser powder bed fusion were amenable to the simultaneous enhancement of strength and ductility. The proposed alloy design approach and duplex nucleation mechanism can guide the tailoring of the microstructure and mechanical properties of additively manufactured aluminum parts. © 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.