Transient Behavior of Inclusion Chemistry, Shape, and Structure in Fe-Al-Ti-O Melts: Effect of Titanium Source and Laboratory Deoxidation Simulation

In the present study, laboratory-scale deoxidation experiments in a vacuum-induction furnace (VIF) were carried out to elucidate the evolution of inclusions during transient stages after a titanium addition. Three different titanium sources (Fe-70 wt pct Ti, Fe-30 wt pct Ti, and titanium granules) were employed and the results were compared in terms of the inclusion chemistry, structure, and morphology. It was found that, immediately after titanium additions to an aluminum-killed melt, titanium-containing inclusions, which are either single-phase or dual-phase particles having a certain amount of titanium and are contrary to melt equilibrium predictions, were formed. Analysis by transmission electron microscope (TEM) suggested that these inclusions could be Al 2 TiO 5 . The change in the inclusion chemistry was accompanied by a shift in the inclusion morphology from spherical to irregular. With time, the inclusion chemistry shifted back toward the thermodynamically stable Al 2 O 3 , but the change in morphology remained. The temporary Al 2 TiO 5 inclusions were formed as a result of local high content of titanium immediately after and at the vicinity of the titanium addition. When comparing the different titanium sources, it was found that they can be ranked as Ti > Fe-70 pct Ti > Fe-30 pct Ti, in terms of the amount of titanium-containing inclusions produced during the transient stage.