A New Constitutive Model for Thermal Deformation of Magnesium Alloys

Abstract

Based on the stress–strain curves of as cast Mg-8Gd-3Y alloy, which were obtained by isothermal compression tests at temperatures ranging from 350 °C to 450 °C and strain rates from 0.001 to 1.5 s−1, a new constitutive model for thermal deformation of magnesium alloys was proposed from the functional relationship between the ratio of instantaneous stress to peak stress (σ/σp) and that of instantaneous strain to peak strain (e/ep). The undetermined parameters of the model were calculated through parameter regression, and the predicted results agree well with the experimental results. To study the applicability and accuracy of the new model, the stress–strain curves of the compression tests of AZ31B and ZK60 alloys in the literature were modeled and calculated by parameter regression, and their predicted values are very close to the experimental values. Then, the new constitutive model was integrated into a finite element software to simulate the load–stroke curves of isothermal upsetting of the specimen with variable cross-section and plane strain forging of Mg-8Gd-3Y alloy. Under six different process parameters, the simulated load–stroke curves are well consistent with the experimental curves. All the results verify the accuracy of the new model for thermal deformation of magnesium alloys.