Abstract:In order to investigate the real-time cracking behavior of each component of a composite with strong interfacial bonding among lamellae, Ti-18Nb (at.%) composite was prepared by spark plasma sintering (SPS), followed by hot-rolling, annealing, and quenching. The microstructure and mechanical properties were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), micro-region X-ray diffractometry (MRXRD), nanoindentation, and in-situ scanning electron microscopy tensile testing. The results show that the Ti-18Nb consists of Ti-enriched, diffusion and Nb-enriched zones, and the sharp Nb gradient across different zones leads to inhomogeneous distribution of phase and mechanical properties. A remarkable finding is that the diffusion zones not only enable the cooperative deformation between the brittle Ti-enriched zones and the ductile Nb-enriched zones but also act as the crack-arresters to prevent the local cracks in the Ti-enriched zones from further propagating across the composite.

Key words: Ti-Nb metal-metal composite; laminated microstructure; in-situ SEM tensile testing; fracture toughness; crack propagation behavior