The microstructure and mechanical property of high niobium TiAl alloy prepared by electromagnetic cold crucible

With the development of aerospace industry, higher requirements are placed on the performance of high temperature structural materials. TiAl alloy, which has low density, high specific strength and specific modulus, good oxidation resistance and creep resistance, has a potential to be widely used in the future. Especially the high niobium TiAl alloys that has been developed in recent years will have more broad application than ordinary TiAl alloys because of higher operating temperature and greater oxidation resistance. In this paper, high niobium TiAl alloys are prepared by electromagnetic cold crucible (EMCC) multifunctional continuous casting technique. The microstructure, element distribution, room-temperature tensile property and high-temperature tensile property of as-cast and the alloy prepared by EMCC are investigated, respectively. The microstructure of high niobium TiAl-based alloys mainly consists of (a₂+?)lamellae, B2 and blocky ? phase. The concentration of Nb in the B2 phase is higher than in the other two phases. Appreciable room-temperature tensile properties, including an ultimate tensile strength of 622 MPa compared with 450 MPa in as-cast condition, were achieved at optimal solidification parameters. As the test temperature increases, the ultimate tensile strength of the alloy has a tendency to increase first at 700ºC and then decrease, which is related to dislocation motion and slip characteristics of intermetallic compound. The results show that the alloy prepared by EMCC has more uniform microstructure, less segregation and great improvement in mechanical properties.