Effect of Mn on Hot Workability and Processing Maps of Al-Mg-Mn 5xxx Alloys

The impact of Mn content (0.1-1 wt.%) on the hot workability and processing maps of Al-Mg-Mn 5xx alloys was investigated. Hot compression tests were carried out in the temperature range of 350-500 °C and strain rate range of 0.001-1 s⁻¹. The processing maps were developed using dynamic material modeling, through which instability regions and safe domains were established. For the studied alloys, two domains with peak power dissipation efficiency were identified: the domains located at 400 °C/0.001 s⁻¹ (Domain I) and 500 °C/1 s⁻¹ (Domain II). With increased Mn level, Domains I and II diminished toward a narrow range of temperature and strain rate and exhibited a decrease in their power dissipation efficiency. For the base alloy, dynamic recrystallization was the principal restoration mechanism in both the domains. In alloys containing higher Mn contents, dynamic recrystallization was significantly suppressed by the presence of Mn-bearing dispersoids. The optimum hot working conditions were determined to be 350-450 °C/0.001-0.007 s⁻¹ for the base alloy with 0.1% Mn. The range of optimum conditions decreased with increasing Mn content and contracted to 375-425 °C/0.001-0.002 s⁻¹ for the 1% Mn alloy owing to the strong pinning effect of the Mn-bearing dispersoids on grain boundary migration.