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Abstract Ternary-layered compound Ti 2 AlN 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 Ti 2 AlN 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 Ti 2 AlN gradually increases to 20%, the high-temperature flexural performance is first strengthened and then deteriorated. 15 vol%Ti 2 AlN/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 Ti 2 AlN particle to the crack propagation, the extended path caused by the crack deflection, as well as the refinement of the TiAl matrix. [ABSTRACT FROM AUTHOR]

The dry-sliding tribological properties of TiAl alloy and its composite Ti2AlN/TiAl were investigated comparatively in the temperature range of 25-800 °C. The wear test results showed the wear resistance of TiAl alloy and Ti2AlN/TiAl composite from 25 to 400 °C was poor, but it improved obviously when temperature was above 600 °C. Also, 15 vol.% incorporation of Ti2AlN particles was beneficial to improve the friction and wear properties of TiAl. Protective oxide layer generated on the wear surface of 15 vol.% Ti2AlN/TiAl composite from 25 to 400 °C, hence, the wear resistance improved. Ti2AlN particles played a load-carrying role and inhabited the delamination of enamel layer effectively when the temperature was above 800 °C. Overall, Ti2AlN particles which acted as hard spots changed the state of wear surface and further provided a second phase strengthening effect, which resulted in the difference in tribological behaviors between TiAl alloy and its composite. [ABSTRACT FROM AUTHOR]

TiAl matrix composites reinforced with Ti2AlN were fabricated by in situ reactive method of powder metallurgy. Microstructures, bending properties at room temperature and compressive properties at elevated temperatures were investigated in contrast with those of TiAl alloy. The results reveal that the microstructure of TiAl matrix is significantly refined due to the synthesis of Ti2AlN. 15 vol.%Ti2AlN/TiAl exhibits excellent bending properties at room temperature, with bending strength of 753 MPa and fracture strain of 0.74%, which are 24.3 and 19.7% higher than those of TiAl alloy. The compressive strength of Ti2AlN/TiAl is markedly improved in comparison to that of TiAl alloy at elevated temperatures. Noticeably, the compressive strength of 15 and 35 vol.%Ti2AlN/TiAl increases by 67.4 and 58.7% at 1000 °C, respectively. The remarkable enhancement of mechanical performance is mainly due to the noteworthy refinement of TiAl matrix and the efficient obstruction of Ti2AlN particles to crack propagation, as well as the effective load-carrying role of Ti2AlN with high elastic modulus. [ABSTRACT FROM AUTHOR]