High-strength aluminum alloy extrusion mechanism: From the perspective of novel tool design and performance enhancement

In this study, a novel rotary extrusion tool made of H13 tool steel was designed for surface strengthening of 7075 aluminum alloy plates. The tool features an arc-shaped extrusion head with a flange connection structure. The effects of rotational speed and extrusion depth on surface morphology, microhardness, tensile properties, residual stress, and fracture mechanisms were systematically investigated. At 1500 rpm and an extrusion depth of 30 μm, the surface exhibited uniform and continuous textured streaks with minimal defects, indicating optimal surface quality. The maximum microhardness (∼300 HV) was achieved at 1500 rpm and 40 μm, while the highest tensile strength (647.985 MPa) and elongation (14.95%) were obtained at 1500 rpm and 30 μm, accompanied by a peak residual compressive stress of −335.08 MPa. Fractographic analysis revealed that increasing rotational speed promoted ductile fracture through enhanced heat input, whereas excessive extrusion depth promoted brittle fracture as a result of intensified mechanical loading. This research provides critical insights for optimizing process parameters to achieve an excellent strength-ductility balance in surface strengthening of 7075 aluminum alloy.