Activities of Fe-B-N and Fe-C-B Systems by Interstitial Solution Theory

Abstract

Solubility of boron in molten Fe-B-N alloy equilibrated with solid BN at 1723K under various partial pressure of nitrogen, and the solubility of carbon in molten Fe-C-B alloy in the temperature range from 1573K to 1723K were measured to determine the thermodynamic parameters of boron in liquid iron.
By using the interstitial model, the activity coefficient of boron at infinite dilution (Ψ_B⁰) and the interaction parameters (θ_i^j) in liquid iron were determined as follows:
lnΨ_B⁰=-5.15, θ_N^B=3.97, θ_B^B=-0.12(1723K)
θ_C^B=18900/T-6.34(1573K1723K)