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.