Ti2 AlC-TiB2 reinforced TiAl matrix composites were synthesized by vacuum arc melting using Ti,Al and B4 C powders as the raw materials.The effects of Ti2 AlC-TiB2 contents on the phases,microstructures and me-chanical properties of Ti2 AlC-TiB2/TiAl composites were analyzed.The results show that Ti2 AlC-TiB2/TiAl com-posites are mainly composed of TiAl,Ti3 Al,TiB2 and Ti2 AlC phases,among which TiAl and Ti3 Al present a kind of lamellar structure and constitute the matrix.With the increasing of B4 C contents in the raw materials,the amount of synthesized Ti2 AlC and TiB2 particles increases,and TiAl grains are refined greatly.In addition,TiB2 and Ti2 AlC particles distribute along the grain boundaries or in the grains.And Ti2 AlC particles are in lamellar or lath-like shapes with an average particle size of about 5-15 μm.The morphology of the TiB2 is related toits content.When the contents of Ti2 AlC-TiB2 ceramic phase are less than 20wt%,TiB2 particles are in a needle-rod shapes with a size of 0.5-5 μm.With the content increases to 30wt%,TiB2 particles grow into blocky faceted particles from 5 -20 μm.The Ti2 AlC is considered to be synthesized from a peritectic reaction between TiC and Ti-Al melt.The av-erage hardness,ductility and the compressive strength of Ti2 AlC-TiB2/TiAl composites increase obviously,with the formation and increase of Ti2 AlC-TiB2 .The mechanical properties of composites with 10wt% ceramic phases show the highest compression strength of 1591 MPa,and its fracture strain is 14% higher than that of pure TiAl alloy. The reinforcing mechanisms of the Ti2 AlC and TiB2 include crack deflection,pinning and pull-out,which is benefit for the strengthening and ductility of Ti2 AlC-TiB2/TiAl 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.

TiAl matrix composites, reinforced with varying Ti2AlC content levels, were synthesized by vacuum arc melting by use of Ti, Al and graphite powders as raw materials. The effects of varied Ti2AlC content from 0 to 100mol% on the phases, microstructures, fracture behaviors and mechanical properties of resulting products were analyzed. Phase transformation was characterized by X-ray diffraction (XRD) and microstructures were measured by scanning electron microscopy (SEM), equipped with energy-dispersive spectroscopy (EDS). Results show that the products are composed primarily of TiAl, Ti3Al, Ti2AlC and small amounts of TiC. The unreacted TiC phase is due mainly to evaporation of Al. The Vickers hardness value of TiAl matrix composite was increased by adding Ti2AlC, while the TiAl/Ti2AlC composite fracture behaviors were improved in terms of crack deflection, trans-lamellar cracking and extraction of carbide reinforcements.