In situ Ti₂AlN reinforced TiAl-based composite with a novel network structure: Microstructure and flexural property at elevated temperatures

Ternary-layered compound Ti₂AlN reinforced TiAl matrix composites with a novel network structure were successfully fabricated through hot-press sintering technique. The microstructure and flexural performance at elevated temperatures were systematically investigated. The results manifest that the in situ synthesized Ti₂AlN distributes around the lamellar TiAl matrix to form the network structure, which transforms from the particle with a size of 1–3 µm to the larger block as the volume fraction extends from 15% to 20%. Besides, the unique structure contributes to the significant refinement of the TiAl matrix. As the volume fraction of Ti₂AlN gradually increases to 20%, the high-temperature flexural performance is first strengthened and then deteriorated. 15 vol%Ti₂AlN/TiAl displays the optimum flexural property with the strength of 791.6, 767.2 and 590.9 MPa at 700, 800 and 900 ℃ which is improved by 28.0%, 35.9% and 25.7% in contrast with that of TiAl alloy. As specifically elucidated through the fracture morphologies, the enhanced flexural property originates from the effective inhibition of Ti₂AlN particle to the crack propagation, the extended path caused by the crack deflection, as well as the refinement of the TiAl matrix.