Influence of Cr, Mn, Co and Ni Addition on Crystallization Behavior of Al(13)Fe(4) Phase in Al-5Fe Alloys Based on ThermoDynamic Calculations

Alloying is an effective method to refine coarse grains of an Al(13)Fe(4) 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 Al(13)Fe(4) nucleus in Al-Fe melt and the formation enthalpy of an Al(13)Fe(4) 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 Al(13)Fe(4) 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: Al(78)(Fe(23)Cr) > Al(78)(Fe(23)Mn) > Al(13)Fe(4) > Al(78)(Fe(23)Ni) > Al(78)(Fe(23)Co), where the formation enthalpy of Al(78)(Fe(23)Ni) is close to Al(78)(Fe(23)Co). Moreover, the presence of Ni promotes the nucleation of the Al(13)Fe(4) phase in Al-Fe alloys, which reveals the mechanism of grain refinement from a thermodynamics viewpoint.