Obtaining <i>γ</i>″ phase by addition of Mn in Mg-Gd-Y-Zn-Ni-Mn alloy: atomic-scale insights by scanning transmission electron microscopy

To develop <i>γ</i>″ phase (hexagonal structure with space group P6¯2m) containing high strength Mg-Gd alloys at lower cost, Mn instead of Ag was added. The state-of-art scanning transmission electron microscopy was applied to characterise <i>γ</i>″ in solution-treated and aged Mg-Gd-Y-Zn-Ni-Mn alloys on the atomic scale. <i>γ</i>″ was not found in the solution-treated state but was captured to precipitate during aging. <i>γ</i>″ with nonuniform occupations of Gd and Y was observed. Different modes of interaction between <i>γ</i>″ and <i>β</i>′ are proposed. The formation of <i>γ</i>″ promoted by Mn was not accidental, suggesting the possibility to form plenty of <i>γ</i>″.