Achieving excellent strength-ductility combination in AA6061 alloy via a novel thermomechanical processing technique

The 6XXX aluminum alloy is widely used in the production of automotive front crash components. Its performance is evaluated based on two key metrics: damage delay and safety reliability, which are influenced by the material's high product of strength and elongation (PSE) and a moderate yield-to-strength ratio (YTS). This study presents an innovative approach using torsion deformation combined with short-term aging treatment to create a gradient structure. This structure integrates gradients in plastic strain, dislocations, precipitated phases, and grain size, forming an in-situ core-shell configuration characterized by a “soft core and hard shell”. As a result, the yield strength, ultimate tensile strength, elongation, YTS, and PSE increased by 4.07 %, 5.72 %, 66.59 %, −1.52 %, and 76.12 %, respectively, compared to the as-received material. Its strengthening effect is significantly better than traditional T6 treatment. Notably, the formation of a gradient structure through this novel thermomechanical processing technique optimized YTS by 11.51 % compared to traditional heat treatments. The significant increase in PSE is attributed to the marked improvement in elongation indicating an effective enhancement in the strength-ductility balance. This provides a promising strategy for designing and manufacturing high-performance components.