Simultaneous enhancement of strength and toughness in TiAl composites via ductile Nb particle addition

Enhancing the toughness of TiAl alloys remains a critical problem urgently requiring resolution. This study demonstrates that the incorporation of 5 vol% ductile Nb particles into the Ti-45Al-8Nb matrix via the spark plasma sintering (SPS) technique simultaneously enhances strength and toughness. The microstructure evolution at the interface between the Nb particles and the matrix was investigated, while the micro-mechanical properties of the interface phases and the toughening mechanisms were analyzed. The results indicate that a multi-layer interface structure is formed between Nb particles and TiAl powders through atomic diffusion reactions involving Nbr/σ/σ+B2/B2+γ/matrix zones. The (B2+γ) reaction layer achieves a gradient transformation of the elastic modulus between the residual Nb particles and the matrix (165 GPa→150 GPa→147 GPa→140 GPa), thereby alleviating the deformation inhomogeneity at the interface. The Nb/TiAl composite prepared at 1250 °C exhibits excellent room-temperature compressive strength (2417 MPa) and fracture toughness (16.85 MPa m^1/2), representing 14.8 % and 13.1 % enhancements compared to pure Ti-45Al-8Nb alloy. These enhancements primarily originate from plastic tearing, interfacial debonding, and bridging of the residual Nb particles. The tough B2 and γ phases in the Nb-rich region improve toughness by reducing fracture energy through crack deflection and branching.