Effect of heat treatment on the microstructure and creep properties of Ti–48Al–2Cr–2Nb alloy produced by selective electron beam melting

This study investigated the effect of heat treatment on the microstructure and creep behavior of Ti–48Al–2Cr–2Nb alloy prepared by selective electron beam melting. The microstructure of the as-built and annealed TiAl alloys exhibited near γ structure and fully (α₂/γ) lamellar structures, respectively. The creep properties were evaluated on the as-built and annealed TiAl alloys under a 250–300 MPa creep stress at 800 °C. The results showed that the creep property was improved significantly by post-heat treatment. The creep rupture life of heat-treated TiAl alloy was 1.6, 2.2, and 2.4 times that of as-built TiAl alloy under the stress of 250, 275, and 300 MPa at 800 °C, respectively. The creep stress exponents of the as-built TiAl alloy and heat-treated alloy were calculated and they were 8.94 and 5.96, respectively. Characterizing the fracture surfaces and deformed microstructure after the creep tests, the as-built alloy exhibited ductile fracture characteristics with numerous dimples. Whereas the heat-treated TiAl alloy displayed brittle fracture characteristics. Finally, the creep fracture behavior was discussed in detail.