Thermally Activated Deformation of Gum Metal: A Strong Evidence for the Peierls Mechanism of Deformation

Compression deformation and stress relaxation tests have been made over a wide temperature range for Ti-based bcc alloy single crystal of Gum Metal composition to elucidate the deformation mechanism. The shear yield stress decreases rapidly with increasing temperature with decreasing slope above room temperature, tending to level off. Activation analysis showed that the activation volume becomes smaller than 10 b(3) (b: the Burgers vector) at high stress, indicating that the deformation is controlled by the Peierls mechanism at low temperature. Similar results have been obtained also for severely cold-swaged polycrystalline Gum Metal with the similar composition. These results contradict the generally accepted dislocation-free mechanism of Gum Metal.