First-principles study of structural, mechanical, and electronic properties of typical iron-containing phases in Al-Cu alloys under different pressures

Abstract The structural, mechanical, and electronic properties of typical iron-containing phases, Al 3 Fe, Al 6 Fe, and Al 7 Cu 2 Fe, in Al-Cu alloys were determined using first-principles calculations. The calculated lattice constants were in good agreement with experimental values. Al 3 Fe exhibited the highest structural stability and most superior alloying ability. Al 6 Fe had the worst alloying ability and required a high cooling rate for its formation during solidification. Al 7 Cu 2 Fe was the easiest to dissolve into the Al matrix because it has the lowest negative cohesion energy. Mechanical properties improved with increasing pressure. Al 3 Fe exhibited the highest stiffness and strongest resistance to volume change and shear deformation. Al 6 Fe had better ductility owing to the high bulk-to-shear modulus ratio and Poisson's ratio; however, it had the lowest hardness and highest anisotropy, leading to a strong tendency for crack initiation. Density of states data showed that no structural variation or phase transformation occurs for any of the phases under applied pressure; moreover, they indicated covalent bonding in Al 3 Fe, accounting for the relatively high structural stability. Finally, all iron-containing phases were confirmed to be paramagnetic.