Stored energy and recrystallization kinetics of ultrafine grained titanium processed by severe plastic deformation

Equal channel angular pressing (ECAP) was conducted at 250 °C on commercial purity titanium up to 10 passes. An ultrafine-grained microstructure with a mean grain size of about 183 nm was obtained. The evolution of stored energy and recrystallization temperature was studied by differential scanning calorimetry. The activation energy involved in the recrystallization process was also determined. The results show that with increase of ECAP passes up to 6 the recrystallization temperature increases. Also, it is seen that with increasing ECAP passes up to 8 the stored energy increases, beyond which it saturates at a value of about 58 J/mol. For the recrystallization of 10 passes ECAP-ed samples, average activation energy of about 342 kJ/mol was determined.