Effect of the interaction between the chemical and the magnetic ordering on the phase equilibria of iron base alloys

It is well known that the magnetic properties such as the Curie temperature Tmag <sub>C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both Tmag c and β of the Ni3Pt （L12） and NiPt （L10） and Tmag <sub>c of the CoPt （L10） and CoPt3 （L12） ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ’-FeNi3 （L12） and the α’-FeCo （B2） ordered compounds have higher Tmag <sub>c and β values comparing with the disordered solution phases, γ （A1） and α （A2）, respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of Tmag <sub>c and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X（X=Al, Co, Ni, Rh, Si） binary systems.The Gibbs energy of the α（A2）, γ（A1） and liquid phases is described by a sub-regular solution approximation. The ordering contribution to the Gibbs energy ,ΔGorder <sub>m, and deviations of magnetic properties, ΔTmag <sub>c and Δβ, of the ordered compounds, FeAl （B2）, Fe3Al （D03）, FeCo （B2）, FeRh （B2）, FeSi （B2）, Fe3Si （D03） and FeNi3 （L12） is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D03 and L12 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.

It is well known that the magnetic properties such as the Curie temperature T^mag __C and the mean magnetic moment β of ordered compounds have different values from those of the disordered solutions. For instance, both T^mag _c and β of the Ni_3Pt (L1_2) and NiPt (L1_0) and T^mag __c of the CoPt (L1_0) and CoPt_3 (L1_2) ordered compounds are strongly depressed due to the ordering compared with those of the metastable disordered Ni-Pt and Co-Pt alloys. On the other hand, the γ'-FeNi_3 (L1_2) and the α'-FeCo (B2) ordered compounds have higher T^mag __c and β values comparing with the disordered solution phases, γ (A1) and α (A2), respectively. In consequence, the stability of the ordered phase is depressed or enhanced due to the interaction between the chemical and magnetic ordering caused by the decrease or increase of T^mag __c and β values. The purpose of this study is to investigate the effect of the interaction between the chemical and the magnetic ordering on the phase equilibria in the Fe-X(X=Al, Co, Ni, Rh, Si) binary systems.The Gibbs energy of the α(A2), γ(A1) and liquid phases is described by a sub-regular solution approximation. The ordering contribution to the Gibbs energy ,ΔG^order __m, and deviations of magnetic properties, ΔT^mag __c and Δβ, of the ordered compounds, FeAl (B2), Fe_3Al (D03), FeCo (B2), FeRh (B2), FeSi (B2), Fe_3Si (D03) and FeNi_3 (L1_2) is introduced by the split compound energy formalism. Effect of the interaction between the chemical ordering, B2, D0_3 and L1_2 and the magnetic ordering on the phase equilibria will be discussed according to the calculated phase diagrams of the Fe-X binary systems.