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 mu m, 400 mu m and 500 mu m were successfully fabricated by reaction hot pressing. The stress-strain curve of the laminated composites with 300 mu m layer thickness exhibits superior tensile elongation (24.5%) and similar strength compared with the laminated composites with 400 mu m and 500 mu m 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. (C) 2014 Elsevier B.V. All rights reserved.