α-Al₂O₃(s)と平衡するFe-Al-O系液体の熱力学の会合溶液モデルによる解析

抄録

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, a_Al,%^\invdiameter 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 logf_O vs. [%Al] and logf_Al vs. [%O] on E.C. are not linear. The discrepancies of the reported values of e_O^Al, e_Al^O and deoxidation constant K′ between various investigators are attributed to the treatments assuming that these relations are linear.