Effect of initial microstructure on hot deformation behavior of AlMg5Si2Mn alloy

Highlights: • Hot deformation behavior in as-cast and homogenized state were investigated. • Microstructures were characterized by light microscopy. • Effect of initial microstructure on flow softening was discussed. • Softening mechanisms were identified. In this study, the hot deformation behavior of high-temperature annealed and as-cast AlMg5Si2Mn aluminum alloy was investigated in compression tests carried out between 350 and 430 °C, with a strain rate of 0.005–0.5 s⁻¹, using a DIL 805A/D quenching-deformation dilatometer equipped with an accessory that allowed hot compression tests to be performed in either a vacuum or an inert gas atmosphere. To reveal the mechanism of hot deformation, the flow stress behavior and microstructural evolution were investigated after the hot compression tests. Constitutive constants for the as-cast and annealed state were then calculated and compared. The results show that the alloy in the annealed state exhibited lower deformation resistance under the same deformation conditions, especially at low deformation temperatures. The activation energies for deformation, Q, for the as-cast and annealed conditions were calculated to be 181 kJ*mol⁻¹ and 169 kJ*mol⁻¹, respectively.