Mechanical behavior of ultrafine-grained titanium rods obtained using severe plastic deformation

We present the results of the investigation of the mechanical behavior of ultrafine-grained (UFG) titanium rods—semifinished products obtained by equal-channel angular (ECA) pressing in combination with subsequent thermomechanical treatment. This material shows ultimately high values of strength (1240 MPa) and plasticity (relative elongation 12.5%) at room temperature. At the same time, at elevated temperatures the UFG titanium exhibits signs of superplastic behavior with large relative elongations and an enhanced strain-rate sensitivity to the flow stress. The greatest elongation at fracture equal to approximately 300% was reached at 500°C and a strain rate of 10−4 s−1. The microstructure and microhardness of the samples after superplastic deformation have been investigated. It has been established that superplastic treatment can favor “structural improvement” of the UFG titanium and further enhancement in its strength.