Precipitation Behavior of Al-Ti-O-N Inclusions in Unidirectionally Solidified Fe-30mass%Ni Alloy

Abstract

The composition, size, morphology and distribution of the Al-Ti-O-N inclusions in the unidirectionally solidified Fe-30mass%Ni alloy were studied under the different solidification conditions as a function of solute contents which were controlled by using the CaO-Al₂O₃-TiO_x-TiN slags. The TiO_x-Al₂O₃ inclusions were observed in the initial contents of Ti=20-110 and N=60-130, while the TiN inclusions were observed in the initial contents of Ti=700-1100 and N=90-150 on mass ppm base. The Ti content and the size of the TiO_x-AL₂O₃ inclusions increased with an increase in the cooling rate. The TiO_x-rich TiO_x-Al₂O₃ and the TiN inclusions were located in last stage of solidification in the interdendritic and the intercellular region. The precipitation of TiN and TiO_x-Al₂O₃ inclusions was discussed by using the segregation models.