First-principles investigation of the mechanical, electronic and thermophysical properties of Q-phase in Al–Mg–Si–Cu alloys

The mechanical, electronic and thermodynamic properties of Q-phase in Al–Mg–Si–Cu alloys have been studied by using first-principles calculations based on density functional theory (DFT). The calculated lattice constants and formation enthalpies are in good agreement with the available experimental and theoretical results. The elastic constants, bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio of Q-phase have been calculated in the present work. The ductility and plasticity, and elastic anisotropy are also discussed. Using Debye model, the Debye sound velocities, Debye temperatures, Grüneisen constants, heat capacities and coefficients of thermal expansion of Q-phase are obtained. Finally, the electronic structure indicates that the bonds of Al–Mg–Si–Cu are of the mixtures of metallic, covalent, and ionic properties.