Recovery of damping and modulus changes following plastic deformation

Abstract A theory is developed which assumes that changes with time in the decrement and modulus of a crystalline material following plastic deformation are a result of dislocation pinning by deformation—induced point defects. This time dependence is based upon the Cottrell-Bilby t 2 3 law for strain-aging. Comparison of the results of the theory with available data shows that the measured time law is that predicted by the theory for specimens which have been deformed between about 0.4 and 4.0 per cent. For smaller and larger deformations, deviations are obtained. Although measurements so far available permit only a qualitative check of the predictions of the theory with regard to the dependence of the recovery rate on purity and deformation, a check of the temperature dependence is afforded by recovery measurements of Young's modulus for copper. From these an activation energy for the migration of vacancies in copper is determined to be 1.0 eV. A number of experiments needed for checking the theory further are proposed.

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