Enhanced compressive creep properties of a Y₂O₃-bearing Ti-48Al-2Cr-2Nb alloy additively manufactured by electron beam powder bed fusion

Electron beam powder bed fusion (EBPBF) was used to fabricate a Ti-48Al-2Cr-2Nb alloy incorporated with 0.2 wt% Y2O3 nano-ceramic powders. Spherical Y2O3 nanoparticles with the particle size of 20-40 nm were uniformly distributed throughout the as-built TiAl alloy, and the average particle size was 30 nm. The effect of Y2O3 nanoparticles on compressive creep properties was investigated and the creep tests were performed at 750 and 800 C-degrees, respectively, with a stress of 250 MPa. The results showed that the compressive creep properties were significantly improved by Y2O3 nanoparticles. After 50h creep test at 800 C-degrees, the maximum creep strain decreased from 59.22% for the Y2O3-free alloy to 28.08% after the incorporation of Y2O3 nanoparticles, and the minimum creep rate decreased from 2.56 x 10(-6) s(-1) to 1.53 x 10(-6 )s(- 1) correspondingly. The maximum creep strain and minimum creep rate of the Y2O3 bearing Ti-48Al-2Cr-2Nb alloy were 110.9% and 67.3% lower than those of the Y2O3-free alloy at 800 C-degrees, respectively. The content of high angle grain boundary (HAGB, >15(degrees)) increased from 62.1% to 92.9% with the creeping temperature increasing from 750 C-degrees to 800 C-degrees for free-particle TiAl alloy. Large amounts of fine recrystallized grains were observed for Ti-48Al-2Cr-2Nb alloy after 50h creep test at 800 C-degrees, while the recrystallization was prevented by Y2O3 nanoparticles addition. Finally, the effect of Y2O3 nanoparticles addition on the strengthening mechanism and recrystallization behavior of TiAl alloy was discussed. This work suggested that the hightemperature performance of TiAl alloy can be tailored by the incorporation of highly thermal-stable Y(2)O(3 )nanoparticles in EBPBF, which is likely to enhance the service temperature of additively manufactured TiAl alloy for high temperature critical applications.