Adiabatic shear fracture in Ti-6Al-4V alloy

Separated specimens of Ti-6Al-4V alloy were dynamically loaded at a strain rate of 3 900 s ^-1 using a split Hopkinson pressure bar (SHPB) apparatus. The fracture features of the separated specimens were investigated by a scanning electron microscope. The results show that adiabatic shear failure occurs in the tested specimens, and two typical areas (dimple and smooth areas) with different features are alternatively distributed on the whole fracture surface. The dimple areas originate from voids generation and coalescence, exhibiting ductile fracture characteristics. Simultaneously, ultrafine grains (UFGs) and microcracks among grains are observed on the smooth areas, indicating that the emergence of UFG areas is caused by the propagation of microcracks along grain boundaries and exhibits brittle fracture characteristics. Fracture occurring in adiabatic shear bands is not uniform and ultimate rupture is resulted from ductile and brittle fracture modes.