Quantitative evaluation of the short-range order strengthening effect on solid solution and GB strength of Mg–Y alloys by ab initio calculations

Short-range order (SRO) plays an important role in improving the mechanical properties of Mg alloys. In this study, we performed first-principle calculations to quantify the effects of SRO on solid solution strengthening (SSS) and grain boundary (GB) in Mg alloys. The SRO has a positive effect on decreasing the stacking fault (SF) energy. It is also identified that the SRO structure prefers to segregate in the twin boundaries (TB) than the SF due to lower segregation energies of the SRO on the TB than it is on the SF. In order to quantitatively correlate the SRO strengthening with the SSS, critical resolved shear stress (CRSS) is proposed based on the volume and chemical misfits. The newly formulated strengthening model predicts the tensile strength of binary Mg–Y alloy accurately, proving that the ab initio calculations can evaluate alloy properties quantitatively from atomistic scale. Graphical abstract: [Figure not available: see fulltext.]