Numerical simulation and process optimization of backward extrusion for 7A60 aluminum alloy tubes

Abstract

7A60 ultra‑high‑strength aluminum alloy seamless tubes are key components in lightweight structural applications, but their backward extrusion poses significant challenges due to the narrow processing window and high deformation resistance. Through numerical simulation and experimental validation, the effects of extrusion temperature (360–450) °C and speed (0.1–5) mm/s on load, temperature field, stress, and strain were investigated. Results indicate that raising temperature reduces deformation resistance, yet excessive heating at the die exit promotes hot cracking; speeds ≥3 mm/s raise the exit temperature to (492–516) °C, exceeding the solidus and deteriorating forming quality. The optimized conditions are 390 °C and 0.5 mm/s, which give the most uniform strain distribution. Extruded tubes exhibit a layered structure from surface to center: fine‑grained zone, mixed‑grain zone, and fibrous structure. The area fraction of secondary phases decreases from 5.5 % in the as-cast state to (3.4–4.9) % in the as-extruded state, depending on the sampling position. Mechanical properties are significantly improved after extrusion, with ultimate tensile strength, yield strength, and elongation reaching 426.8 MPa, 272 MPa, and 14.0 %, respectively.