Temperature dependence of total free energy of activation for dislocation motion. I. Copper crystals after electron irradiation

Thermodynamical analysis is made of plastic deformation to obtain the total reversible isothermal work (free energy) to overcome obstacles. Experiments were carried out to obtain the total free energy through this analysis, and revealed only two stage spectra in the obstacle strength, with transition region in between, after room temperature electron irradiation on copper. Corresponding spectra were also observed in the temperature dependence of the activation energy. A discussion is given in the light of spectrum theory of hardening. The total free energy is found to decrease with increasing electron dose, in a sharp contrast to the hardening after pile-neutron irradiation, which has been considered to be due to the Frank type dislocation loops. Activation entropies of several times of Boltzmann's constant at room temperature, tending to zero at 0 K, are obtained from the total free energies and compared with the analysis of Schoeck.