The mechanical properties, strain rate sensitivity (m) and deformation activation volume (ΔV) are investigated at the experimental temperatures from 20 to 400°С in a Ti₅₀Ni₅₀alloy in a coarse-grained (CG) state with the austenite grain size D = 200 μm and in an ultrafine-grained (UFG) state with D = 700 μm following an ECAP treatment. It is observed that this treatment improves the yield strength of the alloy compared to its CG-state. The strain rate sensitivity, m, is found to be by a factor of 1.5–2 higher than that of CG-specimens; it increases with the temperature in both states of the material. As the temperature of the material in tension increases up to Т = 150–250°С, parameter ΔV increases to its maximum and with a further growth of the experimental temperature to 400°С, parameter ΔV decreases. The deformation activation volume of the alloy in the UFG-state is by a factor of 2–4 larger than that in the CG-state for the same experimental temperatures.