Study of Mn absorption by complex oxide inclusions in Al-Ti-Mg killed steels

In Al-Ti-Mg killed steels, the use of complex deoxidation products, which act as heterogeneous nucleation sites for fine intragranular ferrite, has been acknowledged as an effective way for grain refinement. In this study, we investigated the interaction between Mn solute atoms and different oxide inclusions (such as MgO, MgTi2O4, MgTiO3, Ti2O3, Ti3O5, AI(2)O(3), MgAI(2)O(4)) experimentally and using first principles calculations, to identify the oxides that can effectively lead to the formation of local Mndepleted zones promoting the nucleation of intragranular ferrite. The results show that MgTi2O4, MgTiO3 are effective for partition of Mn atoms into oxides, while MgO, AI(2)O(3), MgAI(2)O(4) are ineffective for the formation of local Mn-depleted zones. Furthermore, the calculations show that Mn atoms exist as a simple solute by replacing Mg atoms in MgO, MgTi2O4 and MgTiO3. Except by forming complex Ti-Mn oxides, such as MnTi2O4 and MnTiO3, Mn atoms can also exist as a simple solute in Ti2O3 by occupying vacancy positions in their crystals. Ti3O5 oxides cannot absorb Mn atoms by replacing Ti atoms in it, meanwhile, the occupying vacancy pattern is not the main reason for Ti3O5 oxides absorb Mn atoms. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.