Microstructural and Mechanical Stability of Gradient-Nanostructured Mg-Li Alloy During Thermal Exposure

Strain-induced gradient nanostructure formation is an effective method for improving the strength of Mg-Li alloys. However, the microstructural and resulting mechanical stability of gradient-nanostructured Mg-Li alloys during thermal exposure have never been studied, thereby limiting their successful application. In this study, we fabricated a gradient-nanostructured Mg-Li alloy by sliding friction treatment and investigated its microstructural and mechanical stability by annealing at different temperatures up to 250°C. The results showed that (1) the lattice parameter c of the Mg phases gradually decreased with increasing temperature, (2) the Mg-Li nanograins exhibited a significantly lower grain growth activation energy (72 kJ/mol) compared with other Mg-based alloys, and (3) the yield strength of the annealed samples was higher than that of the matrix due to synergetic strengthening of the gradient microstructures at the micron scale.