Anisotropy of the Anelastic Relaxation Associated with Interstitial Carbon in Nickel

The behaviour of interstitial C atoms in Ni has been studied by low-frequency 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 behaviour can be accounted for by considering pairs of C atoms occupying the 2nd neighbour octahedral sites. The kinetics of the relaxation is discussed by assuming the relaxation is due to the reorientation of the 2nd neighbour pairs through the 3rd neighbour configuration.