Effects of Mn addition and related Mn-containing dispersoids on the hot deformation behavior of 6082 aluminum alloys

Abstract

The hot deformation behaviors of 6082 aluminum alloys containing different Mn contents (0.05–1.0 wt%) were systematically investigated by uniaxial compression tests in a temperature range of 400–550 °C and strain rate range of 0.001–1 s-1. Prior to the hot deformation, a low-temperature homogenization (450 °C for 6 h) was carried out on direct-chill cast billets to promote the precipitation of Mn-containing dispersoids. The large numbers of dispersoids in the Mn-containing alloys yielded significantly increased high-temperature flow stresses, compared to that of the base alloy without dispersoids. The material constants and activation energies for hot deformation were determined using the hyperbolic-sine constitutive equation and experimental peak flow stress data. The activation energy increased from 191 kJ/mol for the base alloy to 286 kJ/mol for the alloy with 0.5% of Mn. With further increase in Mn content, the activation energy increased only moderately to 315 kJ/mol for the alloy with 1.0% of Mn. The influences of the Mn content and deformation conditions on the dynamic recovery and recrystallization were quantitatively analyzed. The precipitation of dispersoids in the Mn-containing alloys promoted the retardation of the dynamic recovery and inhibition of the recrystallization owing to their strong pinning effect on the dislocation movement and subgrain migration.