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 mu m 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 degrees C, 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.