Insight into the deformation behavior and failure mechanism of TC25G/Ti₂AlNb material fabricated by laser-directed energy deposition

Additive manufacturing to form a gradient material is an effective way of enhancing both the integrity and mechanical properties of components, such as the blades on a turbine disk. Clarifying the heterogeneous deformation behaviors and failure mechanisms is crucial for establishing a relationship between the microstructure and mechanical properties of gradient materials. In this study, a TC25G/Ti₂AlNb material was fabricated by depositing Ti₂AlNb on a TC25G substrate. Experiments were performed to establish the relationship between the microstructure and mechanical properties of the TC25G/Ti₂AlNb material. The UTS and elongation of the TC25G/Ti₂AlNb material at room temperature were 1103 MPa and 5.1 %, respectively. The UTS of the TC25G/Ti₂AlNb material was comparable to those of TC25G and Ti₂AlNb while the elongation was between those of the two alloys. In tensile testing the first zone to yield was the transition zone, and the Ti₂AlNb zone exhibited less strain than heat affected zone and TC25G zone. Subsequently, necking and final fracture occurred within the transition zone close to the Ti₂AlNb zone (TZ_Ti2AlNb). Because the TZ_Ti2AlNb had much greater content of brittle Ti₃Al phase (70.5 %) due to composition dilution and heat input during thermal cycling, which led to the poorest ductility and toughness of TZ_Ti2AlNb among all the zones.