Fracture behaviors and microstructural failure mechanisms of laminated Ti-TiBw/Ti composites

A range of laminated Ti-TiBw/Ti composites with layer thicknesses of 300 μm, 400 μm and 500 μm were successfully fabricated by reaction hot pressing. The stress-strain curve of the laminated composites with 300 μm layer thickness exhibits superior tensile elongation (24.5%) and similar strength compared with the laminated composites with 400 μm and 500 μm layer thicknesses. The higher elongation is characterized by a prolonged strain softening stage and “non-catastrophic fracture” behavior. The fractography of laminated Ti-TiBw/Ti composites comprises two fracture modes; Ti layers exhibit shear fracture with many shear bands accompanying with micro-voids. However, TiBw/Ti composite layers reveal ductile fracture initiated by nucleation, growth and coalescence of micro-cracks. The difference on fracture mechanisms between Ti layer and TiBw/Ti composite layer is determined by the TiBw reinforcement, while high elongation of the laminated Ti-TiBw/Ti composites with thinner layer thickness is probably attributed to the effective size effect. Meanwhile, with the increase of stress and strain during the plastic deformation process, Ti layer and TiBw/Ti composite layer reveal interaction and mutual competing fracture damage behaviors.