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

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 re-sults 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 & gamma;, blocky B2, and a few (& alpha;2/& gamma;) 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 x 1013 to 4.92 x 1014 m- 2. The high-temperature ultimate tensile strength increased significantly from 539 & PLUSMN; 2 MPa to 680 & PLUSMN; 3 MPa at 750 degrees C. The fracture elongation of Ti-48Al-2Cr-2Nb (66 & PLUSMN; 3%) was much larger than that of Ti-48Al-2Cr-2Nb-0.2Y2O3 (19 & PLUSMN; 1%) when tested at 750 degrees C. The ultimate tensile strength and fracture elongation of Ti-48Al-2Cr-2Nb-0.2Y2O3 were 539 & PLUSMN; 6 MPa and 56 & PLUSMN; 1%, respectively, when tested at 800 degrees 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.