Unexpected capture of Guinier-Preston zone and γ″ phase in as-cast Mg-Gd-Y-Zn-Ni-Mn alloy: Atomic-scale insights

Abstract

Abstract Cs-corrected high angle annular dark field - scanning transmission electron microscopy (HAADF-STEM) has been applied to characterize as-cast Mg-Gd-Y-Zn-Ni-Mn alloy. Atomic-scale images of Guinier-Preston (G.P.) zone and γ″ phase (hexagonal structure with space group P 6 ¯ 2\u202fm) on the same plate have been captured unexpectedly, and the subtle difference between G.P. zone and γ″ is reflected by their different extents of segregation of Mn atoms. Density functional theory (DFT) calculations have confirmed that G.P. zone is the precursor of the γ″ phase and predicted the Mn atomic positions in γ″ phase.