Study on hot deformation behavior of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy using a combination of strain-compensated Arrhenius constitutive model and finite element simulation method

Abstract

Isothermal hot compression experiments were conducted on homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy to investigate hot deformation behavior at the temperature range of 673–773 K and the strain rate range of 0.001–1 s−1 by using a Gleeble-1500D thermo mechanical simulator. Metallographic characterization on samples deformed to true strain of 0.70 illustrates the occurrence of flow localization and/or microcrack at deformation conditions of 673 K/0.01 s−1, 673 K/1 s−1 and 698 K/1 s−1, indicating that these three deformation conditions should be excluded during hot working of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy. Based on the measured true stress-strain data, the strain-compensated Arrhenius constitutive model was constructed and then incorporated into UHARD subroutine of ABAQUS software to study hot deformation process of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy. By comparison with measured force-displacement curves, the predicted results can describe well the rheological behavior of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy, verifying the validity of finite element simulation of hot compression process with this complicated constitutive model. Numerical results demonstrate that the distribution of values of material parameters (α, n, Q and ln A) within deformed sample is inhomogeneous. This issue is directly correlated to the uneven distribution of equivalent plastic strain due to the friction effect. Moreover, at a given temperature the increase of strain rate would result in the decrease of equivalent plastic strain within the central region of deformed sample, which hinders the occurrence of dynamic recrystallization (DRX).

Keywords

• Mg-RE-Zn alloy
• Hot deformation
• Microstructure evolution
• Constitutive model
• Finite element simulation