First‐Principles and HAADF‐STEM Study on the Role of Ag in β' Phase Precipitation of Mg‐Gd‐Y‐Ag Alloys

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Abstract In this study, the β' phase in Mg‐Gd‐Y‐Ag alloy is characterized at the atomic scale using a Cs‐corrected high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM). Meanwhile, the influence of Ag doping with different concentrations on the precipitation of β“‐phase configurations is investigated. The calculation of formation enthalpy indicates that an appropriate amount of Ag doping can optimize the atomic arrangement, reduce the nucleation barrier, and thus promote nucleation. The results of the adhesion and interfacial energy show that Ag doping changed the atomic bonding, structural order within the material, and it makes the system unstable. In terms of β” nucleation, the interfacial energy directly affects the nucleation potential barrier. A low interfacial energy is favorable for β' nucleation. Ag doping increases the interfacial energy, thereby raising the nucleation potential barrier and inhibiting β' nucleation. Moreover, the higher the Ag concentration, the more pronounced the inhibitory effect. The electronic structure properties show that within a specific energy range, the electrons in the 4d orbitals of Ag will transfer to the 5f orbitals of Gd. This electron transfer enhances the atomic bonding within the crystal, forms a more stable electronic structure, and further improves the stability of the crystal.

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