Formation pathways for MgO·Al₂O₃ inclusions in iron melt

The crystallization of inclusions plays a decisive role in determining the structure, properties and size distribution of inclusions in steel. MgO·Al₂O₃ (MA) spinel is one of the most common inclusions having great influence on steel performance. Understanding the crystallization pathways of MA from molten steel is important to control their behaviors. Based on the thermodynamic properties of metastable phases of MA calculated by first principle prior to critical nucleus formation, the present work suggests that there are four possible pathways for MA inclusions nucleation from molten iron. According to the four nucleation pathways, the reaction among [Mg], [Al] and [O] could be the most probable pathway leading to MA inclusion formation, while Al₂O₃ reacting with MgO is almost impossible pathway for MA inclusion formation. The size of MA inclusions is dominated by the formation pathways, which have a close relationship with the adding ways of deoxidizer.