Radiation hardening of copper single crystals

Abstract

The effect of nuclear radiation on the mechanical properties of copper has been studied. It has been found that the yield stress, which is substantially increased by the radiation, increases as the cube root of the flux. A strong temperature dependence of the yield stress of irradiated copper is observed with the yield stress being given by a function similar to σ = A — BT 1 2 above 40° K. A Lüders band with slip lines of very large step height is associated with the enhanced yield stress at small strains. At large strains the phenomenon of overshoot is observed. The annealing kinetics of the radiation hardness have also been studied in the temperature range from 25° K to 700° K. Little or no annealing is observed in the region below 80° K. In the region from 80° K to 300° K approximately 20 % of the yield stress is recovered, with the remainder annealing in the range from 600° K to 700° K. These results have been discussed in terms of the possible mechanisms by which the hardening can occur. While by no means conclusive, these data support a dislocation locking mechanism. On the other hand a very close analogy exists between radiation hardening and the hardening which arises from the addition of impurities, e.g. the hardening in α brass. The correlation between work hardening and radiation hardening appears to be quite small.