Kyoko Wasai1 and Kusuhiro Mukai1
1Department of Materials Science and Engineering, Kyushu Institute of Technology, Kitakyushu
Thermodynamic properties of Fe-Al-O liquid alloy in equilibrium with α -Al2O3(s) were analysed by an associated solution model assuming the associated compounds, Fe3Al(a), FeAl(a), FeAl3(a), FeO(a), FeO • Al2O3(a), Al2O3(a) and Al2O(a). The results obtained are as follows.
(1) The calculated equilibrium curve (E.C.), that is, the relation between log [%O] and log [%Al] of the liquid alloy at 1873~2183 K, has a minimun value of [%O] at [%Al]=0.5~0.8 and a minimun value of [%Al] at [%O]=0.007~0.045. This E.C. describes well the experimental data obtained by various investigators. The shape of E.C. characterized by the minimums is caused by the concentration changes of the associated compounds.
(2) Calculated [%Al] of the liquid alloy equilibrated with both Al2O3(s) and FeO • Al2O3(s) is by 1000 times larger than the activity, aAl,%\minuso at 1873 K.
(3) Contents of insoluble Aluminum (lnsol Al) in the liquid alloy were calculated by the assumption that they consisted of solidified associated compounds, FeO • Al2O3(s), Al2O3(s) and Al2O(s) which were insoluble in acid. The calculated and observed lnsol Al contents agreed well each other.
(4) Calculated relationships of log fO vs. [%Al] and log fAl vs. [%O] on E.C. are not linear. The discrepancies of the reported values of eOAl, eAlO and deoxidation constant K' between various investigators are attributed to the treatments assuming that these relations are linear.
associated solution model, iron-aluminum-oxygen liquid, thermodynamics, deoxidation, hercynite, alumina, insoluble aluminum, interaction parameter, theoretical analyses
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