2002 Volume 88 Issue 9 Pages 493-499
"In-situ" observation of the growth of MnS precipitates in Fe-Si alloyswas made on cooling using a confocal scanning laser microscope. The MnS precipitates in δ phase grew fast, but those in γ phase grew slowly. Two calculation models for the growth of MnS precipitates were compared each other. One is "diffusion controlled" model, and the other is "Ostwald ripening" model. In this case, MnS precipitates appeared in solid iron supersaturated with Mn and S, so the growth of MnS precipitates would be represented by "diffusion controlled" model. The "diffusion controlled" model was combined with the diffusion and redistribution model of solute elements during the phase transformation in Fe-Si alloy. If the coefficients of volume diffusion were used for calculation, the size of MnS precipitates by calculation model was much smaller than that by "in-situ" observation. It would be because of the effects of the short circuit diffusion, especially the surface diffusion. So the calculation model was arranged to consider both the surface diffusion and the volume diffusion. The calculation results became agree with the observation results. The size of MnS precipitates was measured in surface area and bulk area, and that in surface area was larger than in bulk area. This fact suggests that the surface diffusion is effective.
