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Determination of the phase boundaries of the wustite solid solution within the context of reduction tests
Author(s) -
Schürmann Eberhard,
Janhsen Urban
Publication year - 1993
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199301023
Subject(s) - wüstite , thermodynamics , phase diagram , isothermal process , chemistry , context (archaeology) , phase (matter) , phase boundary , oxygen , magnetite , materials science , metallurgy , physics , biology , paleontology , organic chemistry
Oxygen reduction measurements performed isothermally on Fe 2 O 3 with CO/CO 2 gas mixtures make it possible, in combination with a system of equations describing the homogeneous wustite phase FeO n , to describe also the boundaries of this solid solution mathematically. Compared with corresponding data determined by Giddings and Gordon on the basis of a literature evaluation, the boundaries of the wustite field are found to shift to a much lower reduction potential. The developed system of equations makes it possible to plot the curves of the same oxygen concentration in the homogeneous wustite phase field of the Bauer‐Glaessner diagram. When comparing the reduction equilibria of the left‐ and right‐hand wustite solid solution boundary with the appropriate literature data there is a good agreement particularly with the measurements of Darken and Gurry. Significantly lower oxygen concentrations are found in the FeO phase diagram, however, especially at high temperatures. New concentration data derived from the systems of equations are also given for the melt equilibria of the wustite phase, which lead to the assertion that the liquidus curves of magnetite, wustite and iron are also shifted to a lower oxygen concentration. The decomposition point of the wustite is found at 570°C, 49.5 %, CO' 2 and 23.2 % oxygen.