Design of an additively manufactured functionally graded material of Ti60-Ti₂AlNb with Nb-enriched intermediate layer

The graded materials hold great potential for the new generation of aero-engines. Strategic design of compositional transition paths is expected to optimize interfacial bonding characteristics and to mitigate precipitation of detrimental phases in the transition zone, thereby effectively enhancing the comprehensive mechanical performance of graded materials. This study focuses on the fabrication of Ti60-Ti₂AlNb graded materials via laser-directed energy deposition (L-DED). Based on thermodynamic calculations, an optimized transition path with Ti₂AlNb + Nb intermediate layer is proposed to suppress brittle phase formation and promote strengthening phase precipitation in the transition zone. The feasibility of this transition path was systematically validated by comparing calculated and experimental results. Results indicate that the designed transition path can effectively reduce the fraction of α₂ phase, and promote the precipitation of O phase by facilitating the transformation of α₂→O phase and its precipitation from B2 phase. The sample with designed path exhibits a room-temperature tensile strength of 1042.8 ± 0.5 MPa and an elongation of 5.7 ± 0.8 %. This study offers a promising approach to regulate the behavior of phase precipitation and optimize mechanical properties through the design of transition paths, providing a foundation for the industrial application of graded structures.