High temperature plastic deformation and self-diffusion in single crystals of aromatic hydrocarbons

Abstract

The temperature dependence of self-diffusion in biphenyl and the stress and temperature dependence of steady state plastic deformation (creep) in naphthalene and biphenyl have been studied at temperatures greater than 0.80 times the absolute melting temperature, and under stresses of 0.1 to 0.2 MN m−2. The results indicate that under these conditions the solids deform by a dislocation climb mechanism. The activation energies for creep are in good agreement with those for self-diffusion. Dislocation concentrations evaluated on the basis of the Weertman analysis of the dislocation climb process are similar to those derived from direct etch-pit counts. These crystals are approximately ten times less plastic than the rotator-phase organic crystals under similar conditions.