Dual nanoparticles in a wrought Al-4.5 wt% Cu alloy to promote strength-ductility synergy

This study proposes an innovative thermomechanical composite process combining semi-solid isothermal treatment (SSIT), double extrusion, and aging to achieve superior strength-ductility synergy in Al-4.5 wt% Cu alloy. The SSIT process effectively refines primary coarse Al₂Cu phases into nanoscale eutectic structures with an interlamellar spacing of ∼58 nm. Subsequent double extrusion fragments and disperses these structures into nanoparticles. Coupled with the dynamic formation of ${\theta }^{\prime }/{\theta }^{″}$ nanoprecipitates during aging, the alloy develops a dual nanoparticle strengthening system embedded within a bimodal grain architecture featuring alternating coarse/fine-grained zones. The processed alloy demonstrates remarkable mechanical properties with a tensile strength of 472 MPa, yield strength of 348 MPa, and elongation of 16.1 %. This work demonstrates that coupling dual nanoparticles with bimodal grain structures enables dual-phase dislocation pinning while alleviating local stress concentrations, providing a scalable strategy for engineering high-performance aluminum alloys.