Evolution of Al2O3 inclusions by cerium treatment in low carbon high manganese steel

The influence of cerium (Ce) treatment on the morphologies, size and distributions of Al₂O₃ inclusions in low carbon high manganese steel was investigated by OM, SEM-EDS and theoretical calculation. The results showed that Ce can modify the morphologies and types of Al₂O₃ inclusions. After Ce treatment, the irregular Al₂O₃ inclusions were replaced by smaller and dispersive spherical cerium oxysulfides. The effects of treatment time and Ce content on the evolution of Al₂O₃ inclusions were examined. It indicated that Al₂O₃ inclusions were wrapped by rare earth inclusions to form a ring like shape Ce-enriched band around the inclusions. Model was established to elucidate the evolution mechanism of Al₂O₃ inclusions. Evolution kinetics of inclusions was discussed qualitatively to analyze the velocity controlled step. It was found that diffusion of Ce³⁺ and Al³⁺ in solid inclusion core and the formed intermediate layer would be the limited step during the evolution process.