The interface between long-period stacking-ordered (LPSO) structure and β' phase in Mg-Gd-Al alloys

Abstract

The interface between LPSO and β' in the Mg-Gd-Al alloys is investigated by the high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) imaging and first-principles calculation. The formation energies of interface structures with different rare-earth-depleted layers (REDL) indicate that the interface structure with three-layer REDL is the most stable. The interfacial phase diagram with the chemical potential of Gd is obtained by the first-principles molecular dynamics analysis of interface energies, indicating that the β'/Mg interface layer in the three-REDL structure is the most stable, and the REDL is not only the Mg atomic layer, but also part of the LPSO phase. Moreover, it is also indirectly proved that the β'/Mg interface layer with three-layer REDL in Mg-Gd-Al alloys will form strong covalent and metallic bonds, and the bond energy is larger and more stable. Therefore, the characterization and calculations of the LPSO and β' interfaces provide a theoretical basis for future interface property analysis and interface design.