Nanoparticle-bands enabled strength-ductility synergy in wrought Al-Cu alloys

• A nanoparticle-bands microstructure was achieved by the composite thermomechanical processing technology. • A novel Al-Cu alloy reinforced by two types nanoparticles was developed with a UTS of 450 MPa and 17.3 % elongation. • New insights into refinement and application of coarse primary Al 2 Cu phase in aluminum alloys were given. Refining the second phase is an effective approach to enhancing the strength and toughness of metallic materials. This paper adopts a novel composite thermomechanical processing technique (pre-annealing, semi-solid isothermal treatment, and post double extrusion) to fabricate a high strength-ductility Al-4.5 wt% Cu binary alloy via the spheroidization and nano-crystallization of the primary phase (Al 2 Cu). The resulting room-temperature tensile strength, yield strength, and elongation reached 450 MPa, 339 MPa, and 17.3 %. The combined effects of dual nanoparticle (i.e. broken nanoparticles and precipitated nanoparticles) strengthening and grain boundary strengthening are identified as the direct reasons for the enhanced strength. The uniformly alternated coarse and fine grain regions in the bimodal grain structure can coordinate deformation, and the dispersed spherical phase can weaken stress concentration, which are important factors for high plasticity. This work offers new insights for developing high-strength ductility hypoeutectic Al-Cu alloys.