Achieving simultaneous strength-ductility-corrosion optimization of solid-state additive friction stir deposited superlight Mg-Li alloy by a hybrid high flow rate Argon/CO₂ shielding atmosphere

High-performance Mg–Li alloys were fabricated via solid-state additive friction stir deposition under a mixed Ar/liquid CO₂ atmosphere, which addresses severe oxidation and unfavorable thermal cycling issues during additive manufacturing. Benefiting from optimized microstructures, the deposited alloys exhibit outstanding comprehensive properties: a surface roughness of 14.32 µm (41.12 µm for the Air group), an ultralow corrosion current density of 10.18 µA·cm⁻², a specific yield strength of 171.72 kN·m·kg⁻¹ and an elongation of 19%, breaking the traditional strength–ductility trade-off. This shielding atmosphere avoids continuous high-purity Ar supply and cuts manufacturing costs, offering an efficient and low-cost route for high-quality additive manufacturing of highly reactive Mg–Li alloys.