ANISOTROPY OF THE ANELASTIC RELAXATION ASSOCIATED WITH INTERSTITIAL CARBON IN NICKEL

The behaviour of interstitial C atoms in Ni has been studied by low-fr equency internal friction measurements using single crystal specimens. The magnitude of the relaxation peak, which appears at 520 K for f = 1 Hz, is the largest when the axis of shear stress is [111], while the peak is virtually absent when the stress axis is [100]. This behaviou r can be accounted for by considering pairs of C atoms occupying the 2 nd neighbour octahedral sites. The kinetics of the relaxation is discu ssed by assuming the relaxation is due to the reorientation of the 2nd neighbour pairs through the 3rd neighbour configuration.