Structural Features and Mechanical Properties of As-cast Ti-22Al-25Nb Alloy

Ti2AlNb-based alloy is a kind of intermetallic compound. It is expected to replace Ni-based superalloys for high-temperature structural applications with a temperature range of 650 similar to 800 degrees C. In this work, a Ti2AlNb based alloy with a nominal composition of Ti-22Al-25Nb was prepared by water-cooled copper crucible induction floating melting method. The structural features of the as-cast Ti-22Al-25Nb alloy were characterized by XRD and SEM. It is found that the main phase of the as-cast Ti-22Al-25Nb alloy can be B2/beta phase or 0 phase, depending on its melting and casting process parameters. The grain size of the as-cast Ti-22Al-25Nb alloy reaches several hundred microns. The mechanical properties of the as-cast Ti-22Al-25Nb alloy were investigated by tensile, compressive and nanoindentation tests at room temperature. The ultimate tensile strength of the as-cast Ti-22Al-25Nb 0 phase alloy and B2/beta alloy reach 1125 MPa and 1031 MPa, with the elongations of 1.32% and 1.82%, respectively. The nanoindentation hardness of the as-cast Ti-22Al-25Nb 0 phase alloy is slightly higher than that of the as-cast B2/beta phase alloy. The tensile fracture and compression fracture of as-cast Ti-22Al-25Nb alloy show obvious cleavage fracture characteristics. In addition, the tensile fracture is mainly intergranular, while the compression fracture is mainly transgranular.