Effect of Severe Forging and Rolling on the Microstructure and Mechanical Properties of Al–Mg–Sc–Zr Alloy

Abstract

The effect of thermomechanical processing combining one- or two-step isothermal multidirectional forging (MF) and sheet rolling on the structure and mechanical properties of alloy 1570C (Al–5Mg–0.18Mn–0.2Sc–0.02Zr (wt %)) was studied. One-step MF was performed at a temperature of 325°C to a true strain (e) of about 12. In two-step MF, deformation was continued at 250°C to e ≈ 6 (total strain of about 18). Subsequent warm rolling with a total strain e ≈ 1.6 (relative strain of about 80%) was carried out at the corresponding temperatures of each MF step, and cold rolling was performed at room temperature. In both MF steps, relatively uniform (ultra)fine-grained structures with a grain size of 2.2 and 1.9 μm, respectively, were obtained. Subsequent warm rolling led to further grain refinement, whereas cold rolling ensured the formation of highly work-hardened (ultra)fine-grained structures with high densities of lattice dislocations. The best combination of technological and service properties, including strength, plasticity, superplasticity, and thermal stability, was reached in sheets after one-step (higher temperature) MF. Lowering the deformation temperature in the second MF step ensured further alloy strengthening, but impaired its room-temperature rollability and led to an essentially complete degradation of the superplasticity of the obtained sheets.