Hot Deformation Behavior of Ultralight Dual-Phase Mg-6li Alloy: Constitutive Model and Hot Processing Maps

Abstract

High-temperature compression tests with dual-phase Mg-6Li alloy were conducted on the Gleeble-3500 thermal-mechanical simulator. Flow stress and micro-structure evolution were analyzed for temperatures (T = 423, 473,523 and 573 K) and strain rates (ε˙=0.001, 0.01, 0.1 and 1 s−1). On this basis, the constitutive model and hot processing maps were established. Besides, the dynamic re-crystallization (DRX) of α-Mg phase, grain orientation and texture composition under different deformation conditions were analyzed by EBSD technology. The experimental results show that the flow stress of Mg-6Li alloy increased with decreasing deformation temperature and increasing strain rate. In addition, the range of instability zone expanded with the increase of strain. The optimal thermal processing temperature was found to be in the range of 500 K–573 K, and the optimal strain rates were between 0.01 s−1–1 s−1. Model-predicted stress values were compared with experimental values for model verification. The 0.9954 correlation coefficient and the 5.48% average absolute relative error shown by the calculation indicate an acceptable accuracy of the model in predicting thermal deformation behavior of Mg-6Li alloy. Moreover, based on our EBSD data and maps analysis, the DRX proportion of α-Mg phase in Mg-6Li alloy was relatively low, and α-Mg phase formed //CD basal texture.

Keywords

• Mg-6Li alloy
• constitutive relationship
• processing map
• texture evolution