Effect of spark plasma sintering temperature on the microstructure and mechanical properties of a Ti2AlC/TiAl composite

The effect of spark plasma sintering (SPS) temperature on the microstructure and mechanical properties of a bulk ultrafine structured Ti2AlC/TiAl composite prepared by SPS of a mixture of mechanically alloyed Ti–Al powder with a composition of Ti–50Al (at%) and 10 vol% carbon nanotubes (CNTS) has been investigated. X-ray diffraction analysis showed that the sintered bulk material mainly composed of γ-TiAl and Ti2AlC phases. The microstructures of the samples were examined using scanning electron microscopy and transmission electron microscopy. It was found that when an SPS temperature of 950 °C was used, the bulk Ti2AlC/TiAl composite had a high density of 98.3%, and a microstructure consisting of a continuous interpenetrating network of Ti2AlC phase and equiaxed TiAl grains with an average size of 300 nm. The compressive yield strength and hardness of the sintered samples reached 2058 MPa and 6.12 GPa respectively. With increasing the SPS temperature up to 1150 °C, the TiAl grains became significantly coarsened, leading to clearly reduced mechanical properties.