Determination of diffusion coefficient of oxygen in α-iron from internal oxidation measurements in Fe-Si alloys

The diffusion coefficient of oxygen in α-iron was determined by internal oxidation measurements on iron alloys with various contents of silicon in a temperature range from 1073 to 11 73 K with particular attention to the effect of oxide particles in the oxidation layer. The oxide in the oxidation layer and the concentration of silicon present as an oxide, as well as the rate constant for penetration of the oxidation front were determined. The diffusion coefficient of oxygen in the layer, D_O¹⁰, calculated using the rate equation for internal oxidation, increases with the increase in volume fraction of the oxide, f¹⁰. This result indicates that the existence of oxide particles accelerates oxygen diffusion. Therefore, the diffusion coefficient of oxygen in α-iron is determined by extrapolating D_O¹⁰to f¹⁰ = 0, giving good agreement with results obtained in our recent investigations.