Stability of ordered L1 2 phase in Ni 3Fe–Ni 3X (X:Si and Al) pseudobinary alloys

Abstract

The phase equilibria between γ (A1) and γ′ (L1 2) in Ni 3Fe–Ni 3Si and Ni 3Fe–Ni 3Al pseudobinary sections were investigated to evaluate the interaction between the chemical and magnetic orderings on phase stability. Order–disorder and Curie temperatures in these sections were determined by means of metallographic observation, electron probe microanalysis, differential scanning calorimetry, electrical resistivity and vibrating sample magnetometry. It was clarified that the γ to γ′ ordering reaction exhibits first-order characteristics with the γ+ γ′ two-phase field and that the Curie temperature of the γ′ ordered phase shows higher deviation from that of the γ disordered phase. Thermodynamic stability of the γ′ phase was discussed in terms of atomic and magnetic orderings, and the γ/ γ′ transition temperature in paramagnetic state for Ni 3Fe phase was estimated by extrapolation to the Ni 3Fe side in the pseudobinary sections.