Effect of LaB6 on the microstructure evolution and mechanical properties of Ti-45Al-8Nb alloy.

High-Nb-containing TiAl alloys have been considered an excellent candidate for demanding high-temperature structural components due to their attractive mechanical properties and low density. However, the intrinsic brittleness at room temperature remains a great barrier limiting its processability. Here a novel alloy design strategy was introduced to improve its ductility from the perspective of grain refinement and removal of oxygen within the matrix. A minor content of LaB 6 was introduced into Ti-45Al-8Nb alloy prepared by vacuum arc melting. La 2 O 3 and TiB ceramic phases were in-situ synthesized owing to the decomposition of LaB 6 additive. The effect of LaB 6 addition on the microstructure and compressive properties of TiAl-based alloys was investigated. The LaB 6 inoculation not only refines the lamellar colonies but also promotes the generation of single γ phases, contributing to the transformation from coarse full-lamellar to refined near-lamellar and even dual-phase colonies. The major fracture mode transformed from inter-lamellar to trans-lamellar to inter-granular with LaB 6 addition increasing. With 0.4 wt% LaB 6 addition, both the ultimate compress strength and fracture strain increased from 1065 MPa and 17.1 % to 1503MPa and 26.98 % respectively. • The (TiB+La 2 O 3)/Ti-45Al-8Nb composites were in situ fabricated by vacuum arc melting Ti, Al, Nb and LaB 6 mixed particles. • The effect of LaB 6 on the lamellar colonies size and phase constitution of Ti-45Al-8Nb was identified. • The compress strength of the composites increased by refined lamellar colonies and TiB precipitates. • An optimal addition of 0.4 wt% LaB 6 was preferred with maximum strength and fracture strain. [ABSTRACT FROM AUTHOR]