Abstract:
Ti
2AlC-TiB
2 reinforced TiAl matrix composites were synthesized by vacuum arc melting using Ti, Al and B
4C powders as the raw materials. The effects of Ti
2AlC-TiB
2 contents on the phases, microstructures and mechanical properties of Ti
2AlC-TiB
2/TiAl composites were analyzed. The results show that Ti
2AlC-TiB
2/TiAl composites are mainly composed of TiAl, Ti
3Al, TiB
2 and Ti
2AlC phases, among which TiAl and Ti
3Al present a kind of lamellar structure and constitute the matrix. With the increasing of B
4C contents in the raw materials, the amount of synthesized Ti
2AlC and TiB
2 particles increases, and TiAl grains are refined greatly. In addition, TiB
2and Ti
2AlC particles distribute along the grain boundaries or in the grains.And Ti
2AlC particles are in lamellar or lath-like shapes with an average particle size of about 5-15
μm. The morphology of the TiB
2is related toits content. When the contents of Ti
2AlC-TiB
2 ceramic phase are less than 20wt%, TiB
2 particles are in a needle-rod shapes with a size of 0.5-5
μm. With the content increases to 30wt%, TiB
2 particles grow into blocky faceted particles from 5-20
μm. The Ti
2AlC is considered to be synthesized from a peritectic reaction between TiC and Ti-Al melt. The average hardness, ductility and the compressive strength of Ti
2AlC-TiB
2/TiAl composites increase obviously, with the formation and increase of Ti
2AlC-TiB
2. 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 Ti
2AlC and TiB
2 include crack deflection, pinning and pull-out, which is benefit for the strengthening and ductility of Ti
2AlC-TiB
2/TiAl composites.