Insights into the mechanical properties and deformation behaviors of Ti₂AlNb/TiAl matrix interpenetrating phase composites with various interfacial characteristics

In this work, the effect of processing parameters on the microstructural characteristics of the Ti₂AlNb/TiAl matrix interpenetrating phase composites (IPCs) was systematically examined, with particular attention to the formation and evolution of the interfacial region. The results show that the IPCs with high relative density ('99.5%) are successfully fabricated. Owing to the mutual diffusion of elements and subsequent phase transformation, a three-layered interfacial structure is formed. As the sintering temperature increases from 1100 ℃ to 1150 ℃, the interfacial microstructure near the Ti₂AlNb side evolves significantly from a multiphase structure containing O, α₂, σ, and β/B2 phases to a heterogeneous interface dominated by O, β/B2, and fine-dispersed ω phases. At higher temperatures (1200 ℃), interfacial thickening/coarsening, and an increased fraction of ω phase are observed. Moreover, the IPCs prepared at 1150 °C/1h/50 MPa exhibit the best balance between strength and toughness, achieving a tensile strength of 378.5 MPa and a conditional fracture toughness of 20.9 MPa·m^1/2. This improvement stems from a gradient multiphase interface (β/B2, O, and fine ω phases) with 16.1% ω volume fraction (VF), which enhances deformation coordination, interfacial load-bearing capability, crack deflection/branching, and the formation of microcracks. Conversely, interfacial thickening and excessive accumulation of brittle ω phase with a VF of 30.2% ultimately deteriorate mechanical properties.