Mechanical performance and oxidation resistance of an ODS γ-TiAl alloy processed by spark plasma sintering and laser additive manufacturing

In this work, the influence of Y2O3 additions on the mechanical properties and oxidation resistance of a Ti-45Al-3Nb (at.%) alloy have been studied. In particular, the mechanical properties from 293 K to 1073 K and oxidation resistance at 1073 K of spark plasma sintered and direct metal deposited material have been examined. At room temperature, higher yield stress (+ 34%) and ultimate tensile strength (+ 14%) at reduced ductility (- 17%) is observed for the oxide dispersion strengthened variant compared to its non-strengthened counterpart. The strengthened variant shows superior strength retention up to 1073 K. Strengthened direct metal deposited material shows similar deformation characteristics as sintered material but suffers from premature fracture due to residual porosity. The addition of Y2O3 increases the oxidation resistance of both sintered and direct metal deposited material. Parabolic growth constants are decreased by -49% and -75% in sintered and direct metal deposited material, respectively. In sintered material the dispersoid size shows only slight changes from 29 nm to 26 nm at 923 K after 987 h and to 32 nm at 1073 K after 924 h demonstrating the high stability of the added particles. TEM analysis reveals abundant grain boundary pinning by the particles contributing to microstructural stability. The results show the potential of oxide dispersion strengthening in titanium aluminides for conventional sintering as well as for additive manufacturing processing routes.