Superplastic deformation mechanisms of coarse-grained rolled Mg-4Y-3RE magnesium alloy

The Mg-4Y-3RE (WE43) magnesium alloy possesses significant advantages such as high specific strength, excellent shock absorption, strong electromagnetic shielding capabilities and recyclability. However, its close-packed hexagonal structure leads to poor plasticity at room temperature, which limits its broader engineering applications. Therefore, superplastic forming at high temperatures is used to manufacture the components from this alloy. This study conducted tensile tests on hot-rolled WE43 rare-earth magnesium alloy with coarse grains at various temperatures and strain rates. The high-temperature superplastic properties were characterized, revealing the intrinsic mechanisms of thermal deformation behavior. The results indicate that the best superplasticity is achieved at 460 °C. This is attributed to the smallest grain size, the weakest texture, and the relatively uniform distribution of the second phase at this temperature. The influence of strain rate on elongation at temperatures among 440 °C∼500 °C is not significant as the impact of strain rate is multifaceted. Meanwhile, the elongation can reach up to 367.7 ± 3.7 % at a strain rate of 0.01s⁻¹, which exhibits the high strain rate superplasticity (HSRS). Under these conditions, the deformation of coarse-grained WE43 rare-earth magnesium alloy is controlled by grain boundary sliding (GBS) and solute drag dislocation creep. Furthermore, the GBS involves deformation coordination mechanisms such as grain boundary diffusion, lattice diffusion, dislocation climbing, and dynamic recrystallization accommodation mechanisms.