Abstract:Cast rods of TiAl alloy with lamellar microstructure were prepared by cold crucible levitation melting using the Ti-47.5Al-3.7 (Cr, V, Zr) alloys with 0.05-0.2% C (at.%, the same below) addition. The effects of carbon content on microstructure and mechanical properties of TiAl alloys was investigated by means of microstructure observation, tensile test at room temperature and creep properties measurement. The results show that the preferred orientation lamellar microstructure can still be obtained after adding 0.05~0.2% C. The volume fraction of the α2 lamellae increases slightly and the lamellar spacing tends to refine with the increase of C content. When the carbon content exceeds 0.1%, fine Ti2AlC-type carbides precipitated inside the α2 and γ lamellae and at the lamellar interfaces as well, and the size and quantity of the carbides increase with the increase of carbon content. The ultimate tensile strength and yield strength of the alloy at room temperature were improved by adding 0.05~0.2% C, and the improvement gradually increased with the increase of C content. The tensile strength and yield strength were increased by 101 MPa and 123 MPa respectively when the carbon content was 0.2%. The creep resistance has been improved significantly by adding carbon. When the carbon content is 0.1%, the creep performance is the best. When compared with the alloy without carbon addition, the plastic creep strain is reduced by half, and the creep rate at the same strain is reduced by more than one order of magnitude. The addition of C element can restrain the generation and multiplication of dislocations at the initial stage of creep. In the primary creep stage, the formation of jogs and debris in the gamma lamellae hindered the movement of dislocation which contributed to the remarkable increase of strain hardening effect of the C-containing alloy. At the same time, the Ti2AlC-type carbides further strengthened the lamellar interfaces and the matrix, and the refinement of the lamellar spacing together improved the gliding resistance of dislocation across the lamellar interface.