Effect of Fast Neutron Bombardment at Various Temperatures upon the Young's Modulus and Internal Friction of Copper

Abstract

Studies have been made of the variations of internal friction and elastic modulus during irradiation of pure copper crystals at a number of temperatures in the range 90°K to 300°K. The results are interpreted in terms of pinning of dislocation lines by radiation defects migrating from their points of origin. In terms of the room temperature value the dislocation pinning rate is 2.5×10⁻² in the range 100°K to 140°K and (from previous measurements) of the order of 2.5×10⁻⁵ at 20°K. On slowly warming the sample after the irradiation, it is found that at 260°K the modulus and decrement begin to move rapidly toward their ``saturation'' values. Presumably, defects ``stored'' in the sample due to a lack of thermal mobility at the irradiation temperature become mobile at this temperature and move to the dislocation lines.