Microstructure and mechanical properties of Y₂O₃-bearing Ti–48Al–2Cr–2Nb alloy prepared by selective electron beam melting

A Ti–48Al–2Cr–2Nb alloy with uniformly dispersed nano-Y₂O₃ addition was prepared by selective electron beam melting. The effects of beam speed on the defects, microstructure and compressive properties were studied systematically. The Y₂O₃ particles gathered and exhibited a feathery structure in the microstructure when the beam speed was 1500 mm/s due to the relatively low cooling rates. The Y₂O₃ displayed an ellipsoidal structure, with an 80 nm size when the beam speed was 2100 and 2400 mm/s. Many nanotwins were observed within the equiaxed γ grains due to the residual stress that was caused by rapid cooling and a different elasticity modulus between the γ phase and Y₂O₃ particles. The orientation relationship between nano-Y₂O₃ and γ-TiAl matrices was determined by selected area electron diffraction and high-resolution transmission electron microscopy. The Y₂O₃-bearing TiAl alloys presented excellent compressive properties at room temperature, with the ultimate compressive strength reaching 3214 MPa, and the compressive strain was 38.05%. Finally, the strength mechanism of Y₂O₃-bearing TiAl alloys prepared under different beam speeds was discussed in detail.