The structural stabilities of Al3(Sc1−xMx) by first-principles calculations

The positive effects of Al3Sc phase on Al–Sc alloys can be promoted by adding to the third elements. The structure properties of Al3Sc when it dissolves the third elements are investigated by first-principles calculations. Special quasirandom structures are developed for the quasi-binary L12 structures. The calculations indicate that the elements of Ti, Zr, Y and Ta tend to substitute for Sc in Al3Sc, while Ni and Si prefer to substitute for Al. The present lattice parameters generally follow the Vegard’s law. The high solubility of Ti and Y in Al3Sc is revealed in the calculated quasi-binary phase diagram.

Research highlights
► The positive effects of Al3Sc phase on Al–Sc alloys can be promoted by adding to the third elements. However, the structure properties of Al3Sc when it dissolves the third elements have seldom been investigated by any theoretical studies. In this paper, the structural properties of Al3(Sc1−xMx) were investigated based on the first-principles calculations combined with the generated special quasirandom structures. The site preferences of the added elements in Al3Sc were clarified from the enthalpies of formation. Besides, the structure stabilities of solid solutions of Al3(Sc1−xMx) were discussed from the mixing enthalpies and Helmholtz free energies.