Research on deformation behavior, microstructure evolution and phase transformation of ultra-light LA93-1(La/Ce) alloy

Isothermal compression tests were conducted out on the Mg-9Li-3Al-1(La/Ce) (wt.%) alloy under different deformation parameter through a Gleeble-3500 thermal-mechanical simulator. The flow curves at high strain rates exhibit a "serrated flow", which is a dynamic strain aging behavior. R=0.9253 and AARE=7.64% quantified the accuracy of the constitutive equations, indicating that this equation has reliable predictive ability. The thermal processing maps indicated that the safe processing region is T=537-623 K, =0.041-0.001 s–1. This alloy has excellent formability. When deformation is at T=473 K, =1 s–1, there are more deformed grains in two phases, and broken β-Li grains distributed in chains along the RD. In addition, some α-Mg phases precipitated from the β-Li phase, distributed along the β-Li grain boundaries, and they were dominated by recrystallized grains with low dislocation density. High-density dislocation regions located both at the grain boundaries and inside the grains. When deformation is at T=473 K, =0.01 s–1, all the deformed grains in two phases decreased with decreasing strain rate, and they transformed more into substructures. The high-density dislocation regions inside the grains gradually disappear. Additionally, the size of precipitated α-Mg phase increased slightly, which is still predominantly located at the grain boundaries. When deformation is at T=623 K, =0.01 s–1, the degree of recrystallisation increases significantly with increasing temperature. The high-density dislocation regions almost disappeared. Interestingly, large amounts of α-Mg grains precipitated inside the β-Li grains.