The influence of the allotropic transformation on the deformation behavior of pure cobalt

Cobalt single crystals have been deformed and subsequently heated (or cooled) through the transformation before further deformation. It has been found the flow stress does not change on passing through the transformation and is dependent only on the deformation history. On the other hand, the work hardening rate θ/G is always found to be low (-0.3 ×10⁻⁴) in the cph phase and much higher in the fcc phase, from 0.5 × 10⁻³ to 2.8 × 10⁻³ depending on the deformation and transformation history. The results are discussed in terms of forest models of work hardening and latent hardening theories. R. T. HOLT, Formerly Graduate Student, Department of Metallurgy, University of British Columbia, Vancouver, British Columbia, Canada,