Microstructure and mechanical properties of Ti60-Ti₂AlNb graded material fabricated by laser directed energy deposition with different compositional transition paths

Titanium-based graded materials exhibiting high specific strength and thermal resistance demonstrate significant application potential in aero-engine blade manufacturing. However, critical challenges persist due to the complex phase precipitation behavior in the transition zone between different alloys, which leads to degradation of mechanical properties. Ti60-Ti₂AlNb graded specimens were fabricated via laser-directed energy deposition and different compositional transition paths were applied to investigate the chemical composition gradients, microstructural evolution, and phase precipitation behavior. Comparative analyses were conducted on the mechanical properties and associated fracture mechanisms of the specimens. Results reveal that linear transition effectively mitigates interfacial discontinuity between different material zones, while the intermediate layer transition significantly reduces the precipitation of α₂ phase by approximately 40 vol% compared to samples with directly connection and linear transition. A distinct improvement in the mechanical properties at both room temperature and high temperature is achieved when the intermediate layer is applied to Ti60-Ti₂AlNb graded material. The room-temperature tensile strength is 1009.0 ± 3.0 MPa with an elongation of 5.5 ± 2.0%; the high-temperature tensile strength is 602.5 ± 5.5 MPa with an elongation of 5.2 ± 0.3%; and the high-temperature creep rupture life at 600 °C and 300 MPa is increased to 61.7 ± 1.9 h.