Interfacial characteristics and mechanical properties of Al2O3/TiAl and YSZ/TiAl ceramic-metal composites

In this work, yttria-stabilized-zirconia (YSZ) was incorporated into the TiAl matrix via spark plasma sintering (SPS) to investigate its effects on the microstructure evolution, interfacial characteristic and fracture behavior. For comparison, Al₂O₃/TiAl composite with the same content was fabricated as a reference material. The YSZ/TiAl composite forms a dual-phase reinforcement structure, in which micron Al₂O₃ and nano ZrO₂ are dispersed in the matrix, leading to a significant decrease of lamellar colony size from 112.94 μm to 44.85 μm. The crystallographic relationship between the two ceramic reinforcements and the TiAl matrix was determined. The YSZ/TiAl interface reveals a transition from incoherent to semi-coherent configuration and diffusion-induced intermediate Al₂O₃ layer. Moreover, 1.5 wt% YSZ/TiAl composite displays superior mechanical properties of 1153 MPa in flexural strength and 8.53 MPa·m^1/2 in fracture toughness. The enhancement in YSZ/TiAl composite can be ascribed to stronger grain refinement strengthening and multiple coupled crack behavior. These findings indicate that enhancing reinforcement contiguity and interfacial coherency are promising strategies for the optimization of high-performance TiAl-based composites.