ANELASTIC RELAXATION IN IRRADIATED Cu-Be

Ultrasonic velocity measurements were made after thermal neutron irradiation of single-crystal Cu specimens containing 700 or 3700 appm Be. Ultrasonic attenuation was measured in similar specimens after 3 MeV electron irradiation. Three anelastic relaxation processes due to self-interstitial-Be complexes were observed. Cu-Be 1 was found to occur near liquid helium temperature ; the temperature dependence of the velocity change suggests that reorientation of the Cu-Be 1 complex may involve quantum mechanical tunneling. Cu-Be 2 produced an attenuation peak at ~2.5 K at a frequency of 10 MHz. Cu-Be 3 appeared simultaneously with 2 as a shoulder on the high temperature side of the 2.5 K attenuation peak