Effect of Er2O3 and Y2O3 on microstructure and mechanical properties of Ti2AlNb alloy

Abstract

Rare earth oxides can significantly refine the microstructure of the cast alloys and improve their mechanical properties. In this study, Er₂O₃ and Y₂O₃ particles were chosen to add into the Ti₂AlNb-based alloy with vacuum non-consumable arc melting method. For the Er₂O₃ particles, it has obvious dissolution and re-precipitation characteristics during melting. While for the Y₂O₃ particles, they are more stable, and aggregated and grew up during melting. These two kinds of Er₂O₃ or Y₂O₃ both have obvious refinement effects on the B2 grains due to their heterogeneous nucleation. Specially, adding Er₂O₃ particles can promote the decomposition of the B2 and α₂ phases and the increases of the O-phase content. But adding the Y₂O₃ particles can inhibits the B2 decomposition and just only promotes the α₂ decomposition into the O-phase. Additionally, the TAC-Er₂O₃ ingot shows the worst mechanical properties at room-temperature due to its large size and grain boundary segregation of the Er₂O₃ reinforcements. Conversely, the TAC-Y₂O₃ alloy exhibits excellent strength and ductility whatever at room- and high- temperatures owing to its fine grain strengthening and effective strengthening of the second precipitated Y₂O₃ phases.