Deformation of α-zirconium in the vicinity of 0.5 tinm

The creep behavior of specimens of α-Zr, machined from the three principal directions of a rolled slab or from swaged rod, has been studied in the temperature range 870 to 975 K, for stresses in the range 5 to 20 MPa. For a given stress and temperature, the creep rate depends on texture, being higher for specimens having their axes parallel to the longitudinal (rolling) direction than for specimens cut from either the transverse or short transverse directions. The activation energy for creep,Q _C, decreases with increasing stress, and becomes approximately equal toQ _D, the activation energy for self-diffusion, only for stresses in excess of about 20 MPa. The stress exponentn increases from 3 at low stresses to about 9 at high stresses, for the range of stresses and strain rates investigated. The results are incompatible with a simple, power-law representation of the steady-state creep rate in whichn is constant, andQ _C =Q _D, independent of stress. It is demonstrated that the data are consistent with models in which the glide process contributes to the stress and temperature dependencies of steady-state creep.