First-principles Calculations of Bulk and Interfacial Thermodynamic Properties of the T₁ phase in Al-Cu-Li alloys

We recently proposed a new, low-energy atomic structure of the Al₂CuLi (T₁) phase using first-principles calculations based on density functional theory [Acta Mater. 145 (2018) 337-346]. Here, we refine the Li positions in the proposed T₁ structure and find that the T₁ phase has a tie-line with Al at finite-temperature by vibrational entropic stabilization on the Gibbs triangle of the ternary Al-Cu-Li system. We also derive a low-energy T₁/Al coherent interfacial structure and find that Ag and Mg solutes are predicted to segregate to the coherent interface, which is in agreement with recent experimental observations by atom probe tomography.