First-principles calculations of the β'-Mg_7Gd precipitate in Mg-Gd binary alloys

The metastable β' phase is often the most effective hardening precipitate in Mg-Gd based alloys.In this paper,the structural,elastic and electronic properties of the recently identified β'-Mg7Gd precipitate in Mg-Gd binary alloys were investigated using first-principles calculations based on density functional theory.The lattice mismatches between the coherent β'-Mg7Gd precipitate and α-Mg matrix are discussed and used to rationalize the experimentally observed morphology of the precipitate.The mechanical properties were investigated through analysis of the single-crystal elastic constants and the polycrystalline elastic moduli.It is found that β'-Mg7Gd is brittle in nature.Strong covalent bonding in β'-Mg7Gd,as inferred from its electronic structure,further explains its mechanical properties.Our theoretical results show good agreement with experimental measurements.

The metastable β phase is often the most effective hardening precipitate in Mg-Gd based alloys. In this paper, the structural, elastic and electronic properties of the recently identified β-MgTGd precipitate in Mg-Gd binary alloys were investigated using first-principles calculations based on density functional theory. The lattice mismatches between the coherent [Y-MgvGd precipitate and α-Mg matrix are discussed and used to rationalize the experimentally observed morphology of the precipitate. The mechanical properties were investigated through analysis of the single-crystal elastic constants and the polycrystalline elastic moduli. It is found that β′-Mg7Gd is brittle in nature. Strong covalent bonding in β′-Mg7Gd, as inferred from its electronic structure, further explains its mechanical properties. Our theoretical results show good agreement with experimental measurements.