Improvement of high temperature mechanical properties of Ni-based oxide dispersion strengthened alloys by preferential formation of Y-Ti-O complex oxide

Y₂O₃ is mainly applied as a dispersoid in Ni-based oxide dispersion strengthened (ODS) alloys. The added Y₂O₃ reacts with Ti and Al at a temperature above 1150 ℃ to form a complex oxide such as Y-Ti-O or Y-Al-O complex oxide. However, previous studies have shown that Y-Al-O complex oxide has relatively coarser particles than Y-Ti-O complex oxide. In this study, Ti was first added to form Y-Ti-O complex oxide, which has relatively fine particles. Subsequently, Al was added to inhibit the formation of Y-Al-O complex oxide, thus improving the high-temperature mechanical properties of ODS alloys. Ni-based ODS alloy powders with composition Ni-15Cr-xTi-1.1Y₂O₃ (without aluminum) were mechanically alloyed using a planetary mill. Thereafter, the mechanically alloyed powders were heat treated to form a complex oxide of Y-Ti-O. A second mechanical alloying was performed by adding 4.5 wt% Al to the heat treated powders. The products obtained after the second alloying were sintered by spark plasma sintering. The phase of the sintered specimens were analyzed using X-ray diffraction, their microstructures were analyzed by transmission electron microscopy and the size distribution of oxide particles was confirmed by image analysis. Moreover, the high-temperature mechanical properties of each composition were analyzed using a hot hardness tester.