Phase stability, electronic, elastic and thermodynamic properties of Al-RE intermetallics in Mg-Al-RE alloy: A first principles study

Electronic structure and elastic properties of Al2Y, Al3Y, Al2Gd and Al3Gd phases were investigated by means of first-principles calculations from CASTEP program based on density functional theory (DFT). The ground state energy and elastic constants of each phase were calculated, the formation enthalpy (ΔH), bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (ν) and anisotropic coefficient (A) were derived. The formation enthalpy shows that Al2RE is more stable than Al3RE, and Al-Y intermetallics have stronger phase stability than Al-Gd intermetallics. The calculated mechanical properties indicate that all these four intermetallics are strong and hard brittle phases, it may lead to the similar performance when deforming due to their similar elastic constants. The total and partial electron density of states (DOS), Mulliken population and metallicity were calculated to analyze the electron structure and bonding characteristics of the phases. Finally, phonon calculation was conducted, and the thermodynamic properties were obtained and further discussed.