Atomic-scale nucleation pathways of MgAl2O4 particle in molten steel

[Display omitted] •Structures and properties of (MgAl2O4)n clusters were obtained.•Five pathways of the clusters of (MgAl2O4)n were discussed.•Atomic-scale nucleation mechanism of MgAl2O4 in molten steel has been discussed. DFT calculation was used to obtain the structures and thermodynamic properties of (MgAl2O4)n clusters. Atomic-scale nucleation pathway of MgAl2O4 has been discussed by two-step nucleation mechanism. (MgAl2O4)n could formed by five pathways, and the possible pathway from highest to lowest is: the reaction of [Mg], [Al] and [O] > the reaction of [Mg], [O] and (Al2O3)n > the reaction of [Mg] and (Al2O3)n > the reaction of [Mg], [O] and bulk-Al2O3 > the reaction of [Mg] and bulk-Al2O3. (MgAl2O4)n could formed more likely by the reaction of [Mg], [Al] and [O] at the high values of log([%Mg][%Al]2[%O]4), more likely by the reaction of [Mg] and (Al2O3)n at the high values of log([%Mg]3/[%Al]2), more likely by the reaction of [Mg], [O] and (Al2O3)n (or bulk-Al2O3) at the high values of log([%Mg][%O]). Thermodynamic driving force for the formation, aggregation and transformation of (MgAl2O4)n increased with the decreasing of temperature.