Enhanced mechanical properties of Mg-1Al-12Y alloy containing long period stacking ordered phase

In this study, a systematic investigation on the effect of solution treatment time (2–8 h) at 540 °C on the microstructure and mechanical properties in as-cast Mg-1Al-12Y (AY112, wt.%) alloy was performed. The results showed that the solution treatment did not cause the growth of grains and the change of texture; however, the mechanical properties had been significantly improved, which was mainly attributed to the precipitation of 18R long period ordered stacking (LPSO) phase in the solution-treated alloys. In addition, the dissolution of β-Mg24Y5 phase and the diffusion of solute atoms during the solution treatment were both beneficial to the mechanical properties. When the as-cast alloy was solution-treated at 540°C for 4 h (T4-4h alloy), the mechanical properties of the alloy are optimal. Compared with the as-cast alloy, the ultimate tensile strength (UTS) and elongation of the T4-4h alloy are increased by ∼23% and ∼179%, respectively. The deformation of the T4-4h alloys was dominated by a combination of basal slip and non-basal slip, and the presence of the LPSO phase effectively inhibited the nucleation of extension twin. Besides, the LPSO phase can also hinder the activation of basal dislocations and the movement of non-basal dislocations. Therefore, the LPSO phase simultaneously improves the strength and plasticity of the alloy.