Activity coefficient of silicon in molten Fe-C-B-Si alloy

The activity coefficient of silicon in the molten Fe-C-B-Si alloy was determined by conducting the following measurements: 1) Equilibrium contents of boron in the Fe-B-Si-N alloys saturated with solid BN under Ar+N₂ gas mixture at 1 723 K, 2) Solubility of carbon in the molten Fe-C-B-Si alloy at 1 573 and 1 723 K, and 3) Equilibrium distribution of silicon between the molten Fe-C-B-Si alloy and molten silver at 1 723 K. By using the interstitial solution model, the activity coefficient and the interaction parameters of silicon in the Fe-C-B-Si alloy were determined to be: θSi/B = 7.54 (ysi<0.15, 1 723K), InψO/Si=-8.7, θSi/Si=18.4 (ySi<0.2, 1 723 K), θSi/C=297 000/T-2.63 (ysi<0.4, 1 573-1 873 K).