Simultaneous enhancement of strength and plasticity in WAAM 2319 aluminum alloy by bidirectional rolling+ heat treatment

Wire arc additive manufacturing (WAAM) enables the integral fabrication of aluminum alloy components with high ribs and thin webs. However, coarse grains, residual crystalline phases (RCPs), and porosity defects weaken mechanical properties and limit applications. Although interlayer plastic deformation during WAAM can improve the microstructure and porosity defect, it exhibits limitations in deformation degree and uniformity. To address this, this study proposes an asynchronous bidirectional rolling process integrated with heat treatment (surface rolling → recrystallization annealing → side rolling → T6 ageing) to enhance the properties of WAAM 2319 aluminum alloy. Compared to conventional rolling, bidirectional rolling demonstrates superior microstructural uniformity and strength-plasticity balance. This superiority stems from the bidirectional rolling combined with intermediate annealing: it refines grains and reduces porosity while inducing alternating compressive-tensile strains within preferentially oriented RCPs. This effectively blunts brittle second-phase particles and accelerates their separation and migration. Consequently, it promotes the formation of longer and thinner θ^′ phases after solution-ageing treatment, thereby enhancing the precipitation strengthening effect. Furthermore, it significantly delays the formation of pore-induced matrix cracking (PIMC) and interfacial bonded voids (IDVs), which alleviates local stress concentrations and thus improves plasticity.