Deformation behavior of TiB reinforced Ti and Ti6Al4V composite particles under in-situ microcompression

To reveal the role of nano-TiB whiskers in micromechanical behaviors of two common titanium composite particles (TCPs), this paper presents experimental investigation on the elastic and plastic deformation of micron-sized Ti-TiBw and Ti6Al4V-TiBw particles. Scanning electron microscope with in-situ uniaxial compression experiment of single TCP was performed within a diameter range of ∼1–5 μm. This study enables detailed insights into the elastic and plastic deformation and geometrical shape evolution of TiBw reinforced TCPs. It is found that, when the particle size decreases, the flow stress and contact yield stress in microcompression for both TCPs exceed the yield strength of bulk composite pillars with identical content of TiB. The contact yield stress is as high as ∼1.5 GPa and ∼1.3 GPa for the smallest Ti-TiBw (D∼1.45 μm) and Ti6Al4V-TiBw (D∼1.78 μm) particles measured, respectively. In elastic-plastic and fully plastic regime, the steady plastic flow for both particles can be maintained over ∼2 GPa till the engineering compressive strain of ε_E ∼ -0.4. Compared with bulk composites, higher strain hardening rate of ∼34.2 and ∼37.5 GPa for Ti-TiBw and Ti6Al4V-TiBw particles demonstrate remarkable pinning capacity induced by nano-TiBw network. No structural damage and microcracks was observed in surface morphology of severely deformed Ti6Al4V-TiBw particles, showing distinctive microscale plasticity. The deformation and strain hardening mechanism for such composite particles have been discussed in terms of grain size, aspect ratio of TiBw and the network architecture.