Microstructure evolution and strengthening mechanism study of Mg-Li alloys during deformation and heat treatment

Microstructural evolution, textural development and strengthening mechanism of α, α+β and β structure Mg-Li alloys during extruding and annealing process were investigated. It showed that, with increasing Li content, the α-Mg matrix was transformed gradually to the β-Li matrix. In the three alloys, for α-Mg structure, the c-axis of close-packed plane of α-Mg was inclined perpendicular to the extrusion direction after extruding. However, for β-Li structure, the c-axis of close-packed plane of β-Li was inclined parallel to the extrusion direction after extruding. During annealing, a new predominance of {11−20} recrystallization texture was observed in α-Mg matrix. However, no recrystallization texture was achieved in β-Li matrix. Additionally, a solid solution strengthening during annealing could be observed apparently in the β-Li matrix. To study and quantify the strengthening behavior, the relationship models between ultimate tensile strength (UTS), yield strength (YS), hardness (HV) and AlLi volume fraction (VF) were defined using mathematical modeling and regression analysis. It showed that the effect of VF on UTS was much more than that of others. In LAZ832-0.2Y, the fitting models for UTS on VF and UTS on YS revealed the relationship of quadratic function. However, in LAZ1132-0.2Y, the fitting models for them exhibited the linear relationship.