Microstructure, fracture toughness and high-temperature tensile property of large size Ti–46Al–5Nb-0.18C-0.3Si alloy with oriented lamella by electromagnetic confinement directional solidification

Abstract In this paper, the microstructure, fracture toughness, and high-temperature tensile property of the directionally solidified Ti–46Al–5Nb-0.18C-0.3Si alloy are investigated. The lamellar orientation of the alloy is parallel to the growth direction under the action of the seed. Due to the convex shape of the solid-liquid interface, the core grain growth preferentially, and a large-size single crystal is formed in the steady-state region. The results show that the fracture toughness of the alloy increases with the increase of the orientation angle, and the fracture behavior changes from interlamellar to translamellar. The alloy with well-aligned lamellar microstructure possesses the excellent high-temperature tensile properties, and the ultimate tensile strength(UTS) and elongation of the alloys are 636.7±24.2MPa and 23.9±5.75% at 800°C,630.5± 38.45 MPa and 20.1±3.6% at 850°C, 606.9± 21.3MPa and 22.6± 0.1% at 900°C, respectively. Additionally, the toughening mechanism and strengthening mechanism are discussed and concluded.