Thermal depinning of dislocations in electron-irradiated copper

Abstract

Electron irradiations of Cu samples have been carried out at −196°C with integrated fluxes up to 10 17 electrons/cm 2 at 1.0 MeV. Modulus (resonant frequency) and decrement measurements show that pinning of dislocations by irradiation-produced point defects occurs both at −196°C during irradiation and, after moderate doses, during annealing up to about 100°C. The reverse effect, or depinning, is studied in some detail in this work. The depinning process, which occurs in the range from about 250°C to about 500°C (depending on point defect concentration), is attributed to the thermal release of defects from dislocations. Activation energies for this process have been found to be quite high (> 2 eV) and to increase with decreasing point defect concentration. Various models of the depinning process are explored, the most promising of which is based on concurrent, competing processes of pinning and depinning.