Change in Slip Mode with Temperature in Ti-0.49 mass%O

The temperature dependence of 0.2% proof stress was investigated in Ti-0.49 mass%O with an alpha single phase. The 0.2% proof stress decreased as the temperature increased from 77 to 573 K. The athermal stress, which was defined as the average of the stress values for which the temperature dependence was absent above 573 K, was found to be 70 MPa. The temperature dependence of the effective stress indicates that the temperature dependence of the effective stress changed at around 400 K. To study the thermally activated process that controls the yielding in Ti, the temperature dependence of the activation volume was also measured. An inverse temperature dependence of the activation volume was found at between 325 and 400 K, suggesting that the thermally activated process of dislocation glide changed at this temperature. Prismatic slip with < a > dislocations was dominant at low temperatures, whereas other slips were activated at high temperatures. The activation enthalpy for the dislocation glide was also measured between 77 and 573 K.