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Polythermal description of the oxygen pressures in the melts of the Subsystems Fe‐FeO n and FeO‐Fe 2 O 3
Author(s) -
Schürmann Eberhard,
Rasim Wolfgang,
Heimann Klaus
Publication year - 1997
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199700562
Subject(s) - liquidus , spinodal decomposition , oxygen , chemistry , mole fraction , miscibility , oxide , analytical chemistry (journal) , phase (matter) , atmospheric temperature range , dissociation (chemistry) , thermodynamics , polymer , chromatography , organic chemistry , physics
The phase equilibria in the Subsystem Fe‐FeO of the Compound System FeO ranging from mole fractions of x o = 0 to x o = 52% are characterised by a wide miscibility gap. Using the van Laar formulation, it is possible, up to mole fractions of x o = 51%, to describe the liquidus line of the iron, the phase boundaries of the miscibility gap and, with the resultant activities a Fe and a FeO n , the oxygen pressures of the liquid phases either side of the miscibility gap, in a manner consistent with the temperature‐dependent, experimental data of the relevant literature. In the overlap range (oxygen mole fractions of 50 − 52%) to the adjacent Subsystem FeO‐Fe 2 O 3 (oxygen mole fractions of 50 − 60), a continuous transition is achieved to the experimentally ascertained oxygen pressures in the liquid oxide melts, these being characterised by a tendency towards Compound formation. These ‐values are very accurately described polythermally by the modified short‐range‐order model with stipulation of the short ranges 3FeO·Fe 2 O 3 and FeO·Fe 2 O 3 , and also of the dissociation reaction 3(FeO) = (Fe 2 O 3 ) + [Fe] and (Fe 2 O 3 ) = 2(FeO) + [O].