Investigation of microstructure and mechanical properties of novel MgLiAlZnY–TiB alloys based on secondary phase prediction by first principle

Abstract

In the work, secondary phases in MgLiAlZnY–TiB alloys (α, α+β, β) were predicted by first principle, and microstructural evolution and mechanical properties of the alloys at different AlTiB contents (0, 0.1, 0.5, 1.0 wt %) were also investigated. The result of prediction showed that Al2Y, AlLi, TiB2 and Al3Ti phases are likely to emerge, and anisotropies of AlLi and Al3Ti are stronger than that of Al2Y and TiB2. In addition, bonding of AlLi and Al3Ti mainly consists of ionic and metallic bonds, and bonding of Al2Y and TiB2 mainly consists of covalent and metallic bonds, in which all covalent bonds contain σ bond. Based on band structure and DOS, they have a positive metallic conductivity. In experimental analysis, Li could transform Mg matrix from hcp to bcc, and TiB2 could refine α-Mg. Except for β-Li alloy, mechanical properties of α-Mg and α+β alloy are obviously enhanced by increasing AlTiB content (as-extruded and as-annealed). During annealing, decomposing AlLi phase in β matrix leads to a strengthening effect of Al solid solution in β matrix. Furthermore, the strengthening effect presents more noticeable with increasing temperature.