Influence of Cr,Mn, Co and Ni Addition on Crystallization Behavior of Al13Fe4 Phase in Al-5Fe Alloys Based on ThermoDynamic Calculations

Alloying is an effective method to refine coarse grains of an Al₁₃Fe₄ phase and strengthen Al-Fe alloys. However, the grain refinement mechanism remains unclear in terms of the thermodynamics. Herein, the influence of M-element, i.e., Cr, Mn, Co and Ni, addition on the activity of Al and Fe atoms, Gibbs free energy of the Al₁₃Fe₄ nucleus in Al-Fe melt and the formation enthalpy of an Al₁₃Fe₄ phase in Al-Fe alloys is systematically investigated using the extended Miedema model, Wilson equation, and first-principle calculations, respectively. The results reveal that the addition of different M elements increases the activity of Fe atoms and reduces the Gibbs free energy of the Al₁₃Fe₄ nucleus in Al-Fe melt, where the incorporation of Ni renders the most obvious effect, followed by Mn, Co, and Cr. Additionally, the formation enthalpy decreases in the following order: Al₇₈(Fe₂₃Cr) > Al₇₈(Fe₂₃Mn) > Al₁₃Fe₄ > Al₇₈(Fe₂₃Ni) > Al₇₈(Fe₂₃Co), where the formation enthalpy of Al₇₈(Fe₂₃Ni) is close to Al₇₈(Fe₂₃Co). Moreover, the presence of Ni promotes the nucleation of the Al₁₃Fe₄ phase in Al-Fe alloys, which reveals the mechanism of grain refinement from a thermodynamics viewpoint.