Microstructural Formation and Creep Resistance of Sintered Titanium Aluminides with Co and Ni Addition

One of the most effective approaches for the densification of titanium aluminides processed by powder metallurgy involves the addition of elements that induce the formation of a liquid phase during sintering. This work investigated the sintering behavior and creep resistance of Ti-45Al (in at.%) with ternary Co or Ni additions. Conventional sintering under a high vacuum atmosphere led to densifications of approximately 90% of the theoretical density in the Ti-45Al-2Co and Ti-45Al-2Ni alloys, while binary Ti-45Al was limited to a maximum of 57%. Microstructural analysis revealed the formation of equilibrium intermetallics γ-TiAl and α2-Ti3Al, along with Ni- and Co-rich regions concentrated at the boundaries of primary particles. Compression creep tests at 800°C under a 120 MPa load demonstrated a significant increase in mechanical strength, especially with the addition of Co, which showed 1% of plastic deformation in approximately 18 hours.