Constitutive Behavior and Processing Map of As-cast Mg-8Y-6Gd-1Nd-0.17Zn Magnesium Alloy Com-pressed At Elevated Temperature

Abstract:

The constitutive behavior and hot workability of as-cast Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy during the hot compression were investigated at elevated temperature (350 °C ~ 450 °C) and different strain rates (0.0001 s?1~0.1 s?1) under the ultimate compression ratio of 50%. The relationship among these deformation parameters of Mg-8Y-6Gd-1Nd-0.17Zn alloy could be adequately characterized by a sine hyperbolic equation. The experimental results show that both temperature and strain rate have important effects on the flow stress behavior of Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy, and the flow stress increased with lower temperature and higher strain rates. Typical dynamic recrystallization character is found in the true stress-strain curves when samples compressed above the temperature of 400 ℃. The activation energy (Q) and stress exponent (n) during deformation were 359.258 kJ/mol and 5.24, respectively. The average error (ARE) between experimental and calculated values is 3.37%. Then, the processing map was also established and analyzed based on dynamic material model. Considering the processing map and microstructures observation, the optimum hot-working parameters of the alloy were determined to be at a temperature of 400 °C ~ 450 °C and a strain rate of 0.0001 s-1 ~ 0.001 s-1.

Key words:Mg-Gd-Y-Nd-Zn magnesium alloy; hot compression; microstructure evolution; constitutive equation; processing map