Structural features and mechanical properties of as-cast Ti-22Al-25Nb alloy

Abstract:

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 650-800 ℃. In this work, a Ti2AlNb based alloy with a nominal composition of Ti-22Al-25Nb is prepared by water-cooled copper crucible induction floating melting method. The structural features of the as-cast Ti-22Al-25Nb alloy are characterized by XRD and SEM. It is found that the main phase of the as-cast Ti-22Al-25Nb alloy can be B2/? phase or O 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 are investigated by tensile, compressive and nanoindentation tests at room temperature. The ultimate tensile strength of the as-cast Ti-22Al-25Nb O phase alloy and B2/? alloy reaches 1125 MPa and 1031 MPa respectively, with the elongation of 1.32% and 1.82%. The nanoindentation hardness of the as-cast Ti-22Al-25Nb O phase alloy is slightly higher than that of the as-cast B2/? 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.

Key words:Ti-22Al-25Nb; induction floating melting; structural features; mechanical properties