Internal Friction Peaks in Pure Aluminum Observed between 45 and 72°K after α‐Particle Irradiation

Relaxation peaks in aluminum found after α‐irradiation at 21.4°K are discussed. In the temperature region of 40 to 75°K, four peaks are observed which anneal out in stage II with first order kinetics. Two of them show the natural line‐width. From the annealing behaviour, the peaks are ascribed to the reorientation of interstitial clusters containing more than two interstitials. The activation energy for reorientation is significantly different from that for annealing.