Oxide Solubility Minimum in Liquid Fe- M-O Alloy
Abstract
The origin of the solubility minimum of oxide ( {M}_xO_y) in liquid Fe- M-O alloy was investigated, and the minimum was predicted based on thermodynamic calculations. Due to the characteristic property of activities of M and O in the liquid, a maximum exists in the product between the two activities if the affinity of M to O is significantly high, as most deoxidizing elements are. A critical activity product is defined, which is an indicator of the solubility minimum of the {M}_xO_y in the liquid Fe- M-O alloy according to the following relationship: {{max}}(a_M^x × a_{\underline{{{O}}}}^y) = {K_{M_x{{O}}_y}× a_{M_x{{O}}_y}}, where the a_{M_x{{O}}_y} is unity if the alloy is in equilibrium with the pure M_x{{O}}_y. The origin of the solubility minimum was explained using the change of the activity product by composition. Available CALPHAD assessments for several binary Fe- M liquid alloys and Wagner's solvation shell model were combined to calculate the activity product in the Fe- M-O alloy, which can be used to predict the solubility minimum of {M}_xO_y. A favorable agreement was obtained when M = {Al}, B, Cr, Mn, Nb, Si, Ta, Ti, V, and Zr. The Gibbs energy of dissolution of O in pure liquid M (Δ g^circ _{\underline{{{O}}}(M)}) and the Gibbs energy of the formation of {M}_xO_y per mole of atoms (Δ g^circ _{M_x{{O}}_y}/(x+y)) play important roles in determining the solubility minimum, as long as an interaction between Fe and M is less significant than the interaction between metal (Fe and M) and O. Predictions of the solubility minima of CaO and MgO were not satisfactory, requiring further improvement of the present analysis.
- Publication:
-
Metallurgical and Materials Transactions B
- Pub Date:
- December 2019
- DOI:
- 10.1007/s11663-019-01663-4
- Bibcode:
- 2019MMTB...50.2942K