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

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 (Al2Cu). The resulting roomtemperature 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.