SEM in situ study on the mechanical behaviour of SiCf/Ti composite subjected to axial tensile load

Ti–6Al–4V matrix composites reinforced by SiC fibers with and without carbon coating (SiCf/Ti–6Al–4V) were prepared by Foil–Fiber–Foil (FFF) method and subjected to heat treatment at 900 °C for 50 h. Subsequently in situ Scanning Electron Microscopy (SEM) technique was used to study fracture mechanism of the composites under axial tensile loads. The influence of fiber coating, interfacial reaction zone and titanium alloy microstructure on initiation and propagation of cracks was investigated in detail. The results show that upon loading, the non coated fibers crack and fracture into smaller fragments. However, the carbon coated fiber does not develop any fracture during the entire experiment and a part of the fiber is pulled out during the final fracture.

Research highlights
► Pre-loading cracks are observed in interfacial zone of fiber without coating.
► No pre-loading cracks are observed in the interfacial zone of carbon coated fiber.
► Upon loading, the non-coated fibers fracture into a number of small fragments.
► The carbon coated fiber has a weak interface and resists fracture.
► The carbon coated fiber does not fracture and is pulled out on final fracture.