Learning about the nucleation pathway of MgO•Al2O3 spinel from an Fe-O-Al-Mg melt using a two-step nucleation mechanism

The crystallization process from a melt begins with nucleation, which determines the structure and size of the resulting crystal embryos. Further understanding of multi-pathway crystallizations from a melt through two-step nucleation mechanisms is needed. The formation mechanism of MgO center dot Al2O3, which sheds light on the metastable structures or pathways leading from the molten steel to the solid crystal, was analyzed to improve the understanding of the fundamentals of MgO center dot Al2O3 spinel inclusion. Here a pathway of formation that derives from a variety of metastable structures in earlier crystal nucleation stages was discovered, which drives the formation of MgO center dot Al2O3 more strongly than the traditional mechanism in which it originates from oxide-based inclusions (MgO/alpha-Al2O3). This study uncovers the behavior of the early stages of inclusions crystallization in steels, extends the classical MgO center dot Al2O3 formation theory and highlights the possible pathway to form MgO center dot Al2O3.