Effect of carbon reactant on microstructures and mechanical properties of TiAl/Ti2AlC composites

TiAl/Ti2AlC composites were successfully synthesized by vacuum arc melting with TiC, graphite powder, and carbon nanotubes (CNTs) as carbon sources. As the amount of Ti2AlC ceramic increased, the microhardness and compressive strength of the TiAl/Ti2AlC composites improved linearly. Importantly, the TiAl/Ti2AlC prepared with TiC as the carbon source exhibited higher microhardness and compressive strength than that composites prepared with graphite powder or CNTs. During vacuum arc melting, three reactions occur successively: Ti+Al→TiAl, Ti+C→TiC, and TiAl+TiC→Ti2AlC. Ti2AlC was formed by peritectic reaction between the TiAl melt and TiC particles. A large amount of TiC was left in the TiAl matrix, which acted to improve the hardness and strength of the composites. The fracture behavior of the composite was mainly transgranular fracture. The pinning, pulling out, and the effect of crack deflecting of TiC particles, together with the interlayer tearing, plastic shearing, folding, and crimping of Ti2AlC played a key role in the improvement of the strength and plasticity of the composites.