Evolution of Al-Ti Oxide Inclusion during Isothermal Heating of Fe-Al-Ti Alloy at 1573 K (1300 °C)

Evolution of Al-Ti oxide inclusion during 3 hour isothermal heating of Fe-Al-Ti alloy at 1573 K (1300 °C) was studied. Homogeneous spherical Al-Ti oxide inclusion with nonstoichiometric composition was observed in two as-cast alloys. After heating, most of the homogeneous Al-Ti oxide inclusions changed to heterogeneous ones with Al-rich and Ti-rich parts, while the remaining homogeneous oxides were rare in both alloys. The concentration gradient of Al and O was observed inside the heterogeneous inclusion. The size distribution extended more broadly, and the shape changed from spherical to irregular. The mechanism of the variation was proposed as the diffusion of Al and O in the homogeneous inclusion from the inside to the surface of inclusion to precipitate alumina during heating.