Effect of low-temperature rolling on the tensile behavior of commercially pure tungsten

We have evaluated the tensile behavior of commercially pure tungsten (W) as a function of low-temperature rolling. It is observed that rolling below the nominal recrystallization temperature 1523 K (1250 °C) concomitantly enhances the ductility and strength of W. Strain-rate jump tests and stress-relaxation experiments show that low-temperature rolling also renders reduced strain-rate sensitivity and activation volumes associated with the plastic deformation of W. For W samples rolled at 873 K (600 °C), with a total equivalent strain of ∼2.5 (including a previous rolling strain of 1.7 introduced at 1073 K [800 °C]), the activation volume for plastic deformation is around 10b3 (b is the magnitude of the Burgers vector of W). This is in agreement with a double-kink mechanism with the spreading between the kinks controlled by the forest dislocation density. Fractographic observations indicate that the rolled W exhibits a laminar structure. The layer thickness is a function of rolling temperature, rather than a function of rolling strain introduced.