Subsolidus Phase Equilibria of Fe-Ni-X-O (X = Mg, Al) Systems in Air

Abstract

The phase equilibria of Fe-Ni-X-O (X = Mg, Al) systems, including their lower-order systems, at temperatures between 1200°C and 1600°C in air in the subsolidus region, have been experimentally studied. In the present study, the 'Fe 2 O 3 '-MgO, 'Fe 2 O 3 '-Al 2 O 3 , and NiO-Al 2 O 3 binary phase diagrams, as well as the ternary phase diagrams in the Fe-Ni-Mg-O and Fe-Ni-Al-O systems projected onto the Fe-Mg-Ni and Fe-Al-Ni planes, have been constructed. Differences have been found between the present measurements, the previously published data, and the FactSage predictions, especially in the lower-order systems. It is suggested that the improved experimental techniques used in the present study, which involve carefully planned equilibration procedures followed by electron probe X-ray microanalyses (EPMA), provide more accurate and precise measurements of the phase boundaries and phase compositions.

Thermodynamic modeling of the aluminum–iron–oxygen system

“…However, none of the ternary oxides showed to dissolve any significant concentrations of ZnO and the compositions could therefore be regarded as very close to the Fe 2 O 3 -Al 2 O 3 section. Hansson et al [40] also used EPMA for their phase composition determinations and notably concluded similar discrepancies compared to previous data as Rhamdhani et al [37] would do some years later.…”

“…The tetrahedral sites and the regular octahedral sites have preference for Al whereas Fe prefers the two irregular six-fold sites. Although non-stoichiometric compositions have been observed [36,37], it is modeled as a stoichiometric compound in the current work for the sake of simplicity. Its Gibbs energy function is hence given by…”

“…In addition to the experiments, the study by Rhamdhani et al [37] included thermodynamic calculations using the FactSage [6] software. The method to develop the thermodynamic descriptions utilized by FactSage is similar as the current approach, and it should be noted that the modeling work in the Al-Fe-O system for the FactSage database has been mentioned in the literature [10,41].…”

“…Other measurements by Muan and Gee [36] show different phase regions; one-phase spinel (represented by  ), one-phase liquid (represented by ◇), two-phase region AlFeO 3 / corundum (represented by ⋈), two-phase region spinel/liquid (represented by ☐) and two-phase region corundum/liquid (represented by ⊕). disordered contribution is then subtracted from the SGTE expression and the resulting expression is used for the end-member Interaction parameters for the corundum phase are evaluated by accounting for the experimental information on the phase equilibria in the Al 2 O 3 -Fe 2 O 3 section [37,52] and thermochemical data by Majzlan et al [35]. The most recent experimental investigation by Rhamdhani et al [37] is given a high weight in the evaluation.…”

Identification of Oxide Phases in Oxide Dispersion Strengthened PM2000 Steel

“…16,17) For the commercial PM 2000 steel, detailed processing procedures are not available. It has been reported that the Al2Fe2O6 phase formed at a temperature of about 1 318-1 410°C 18) and 1 300-1 400°C, 19) whereas the Al3Ti5O2 phase formed at a relative low temperature of 900°C. 20) High pressure and severe plastic deformation during hot isostatic pressing and hot-rolling processes accelerated probably the formation of the Al2Fe2O6 phase, i.e., it formed at lower temperature.…”