Spark Plasma Sintering of TaN/TiAl Composites: Microstructure and Microhardness Study

Titanium aluminide (TiAl)-based materials have attracted much attention in the aerospace and automobile industries due to their attractive properties. Studying the microhardness of these materials as it relates to the as-sintered and heat-treated state is of interest in this article. TiAl and TiAl-based composites with varying additions of Tantalum nitride (TaN) content (2, 4, 6, 8 wt.%) were prepared by spark plasma sintering technique. The samples were sintered at 1150 °C, 100 C/min, 50 MPa, a dwell time of 10 mins, and fully dense characteristics as their relative densities were above 98 %. The microstructure and microhardness of the sintered samples were examined. Also, the sintered samples' microhardness was evaluated after the heat treatment process at 750 °C. It was observed that the relative density of the composites dropped at 2 and 8 wt.% addition of TaN, while the addition of TaN significantly increased hardness value in the as-sintered and heat-treated condition, from 304 HV to a maximum of 499 HV in the as-sintered state. The microstructures revealed that the reinforcement was segregated to the gamma phase, interlocked by the lamellar colonies.