First-principles calculations of structural stability and elastic properties of REB12 strengthening phases in boriding Mg-RE alloys

The effect of rare-earth elements (REs) on formation and elastic properties of strengthening precipitates in boriding Mg-RE alloys was determined by first-principles calculations. The preferential formation of a B12-cluster during boriding process results in the appearance of the only REB12 strengthening phases. The REB12 compounds possess the high hardness, which is mainly associated with the strong covalent bondings of B12-cluster. The RE types hardly affect the hardness of REB12 compounds, which is partially elucidated owing to a low fraction of RE-B metallic bondings.