Effects of yttrium oxides on the microstructure and mechanical properties of 15-15Ti ODS alloy fabricated by casting

Abstract The emphasis of oxide dispersion strengthened (ODS) steels is on the size, morphology, and distribution of the oxide particles. In this paper, the behavior of yttrium oxides particles in 15-15Ti alloy fabricated by casting was systematically investigated, and the microstructure of as-rolled, solid solution and as-recrystallized specimens was characterized. The X-ray diffraction results indicated that the secondary phases in 15-15Ti alloy are composed of YTaO4, YFeO3, Y2O3 and metal carbides. The thermodynamic simulation results and the observed microstructure suggest that the coarsening and agglomeration of yttrium oxides occurred during solidification. After 80% cold rolling and recrystallization annealing, yttrium oxides were refined and distributed more uniformly with typical sizes of about 50–100 nm. As a result, the microstructure of 15-15Ti alloy with dispersed yttrium oxides particles was achieved. Compared with the conventional 15-15Ti alloy (3.67 alloy), new 15-15Ti alloy has a higher ultimate tensile strength of 690 MPa and yield strength of 523 MPa. Accordingly, these results indicated that 15-15Ti alloy exhibited excellent mechanical properties.