Significant enhancement in high-temperature tensile strength of trace nano-Y2O3-reinforced TiAl alloy prepared by selective electron beam melting

Abstract

In this study, the effect of 0.2 wt% Y2O3 nanoparticles addition on the microstructure and elevated-temperature tensile properties of TiAl alloy prepared by selective electron beam melting (SEBM) were investigated. The results indicated that the microstructures of Ti–48Al–2Cr–2Nb and Ti–48Al–2Cr–2Nb–0.2Y2O3 alloys were similar, except for the homogeneous distribution of Y2O3 nanoparticles, which were mainly composed of equiaxed γ, blocky B2, and a few (α2/γ) lamellar colonies. The nano-Y2O3 particles induced a large number of dislocations and twins around the reinforcing particles due to the thermal mismatch caused by rapid heating and cooling during SEBM layer-by-layer fabrication, and the density of geometrically necessary dislocations increased from 5.70 × 1013 to 4.92 × 1014 m−2. The high-temperature ultimate tensile strength increased significantly from 539 ± 2 MPa to 680 ± 3 MPa at 750 °C. The fracture elongation of Ti-48Al-2Cr-2Nb (66 ± 3%) was much larger than that of Ti-48Al-2Cr-2Nb-0.2Y2O3 (19 ± 1%) when tested at 750 °C. The ultimate tensile strength and fracture elongation of Ti-48Al-2Cr-2Nb-0.2Y2O3 were 539 ± 6 MPa and 56 ± 1%, respectively, when tested at 800 °C. Finally, the strengthening mechanism attributed to the added Y2O3 nanoparticles was discussed. These findings provided us an important reference for enhancing high-temperature mechanical properties of TiAl alloys.