Hot deformation behavior of magnesium alloys: A comprehensive review of plastic flow, deformation mechanisms, constitutive modeling and processing maps analysis

This review paper offers a comprehensive analysis of the hot deformation characteristics, microstructural changes, and the derived constitutive equations for the flow stress forecast, and processing maps development in magnesium alloys. The present discourse elucidates the capacity of hot working to enhance the grain structure of Mg alloys by dynamic recrystallization (DRX), mitigate structural flaws, and improve the alloys’ mechanical properties. This work offers an in-depth analysis of the thermomechanical behavior and restoration mechanisms of DRX and dynamic recovery (DRV). Additionally, the impact of phase occurrence, dynamic precipitation, and the composition of the alloy on these thermomechanical phenomena is examined. To discover the best working parameters and pinpoint the instability/unsafe regions—which include flow instability, cracking, and other structural defects—during the hot deformation process of magnesium alloys, this study addresses the adoption of processing maps. Constitutive modelling of flow stress data was also explored to characterize material flow under various deformation conditions, such as the strain, temperature, and strain rate. In particular, the incorporation of the threshold stress (to account for the impact of phase occurrence and their precipitation during hot working process), diffusion coefficient and temperature-dependent Young's modulus are discussed. In addition, we explore the correlation between the experimentally measured deformation stress exponent values and activation energy values, and those predicted by creep theories. Additionally, this study evaluates the analysis of several modeling approaches and equations utilized in forecasting flow curves throughout the process of hot working. Lastly, some suggestions for possible future study directions are provided.