Probing diffusional jumps in ordered compounds by anelastic relaxation spectroscopy

Intrinsic point defects may give rise to anelastic relaxation effects in ordered compounds in which some of the sublattice sites have lower symmetry than the host lattice. Detailed experiments have been carried out on one of such effects: the relaxation effect in Ni3Al, which was interpreted to be due to stress-induced reorientation of antisite Al atoms in the Ni-sublattice (Numakura et al. 1999), focussing on the effects of deviation of composition from stoichiometry. The relaxation strength has been found to increase sensitively with increasing Al concentration, supporting firmly the earlier interpretation. The observed relaxation rates have been analysed on the basis of the mechanism of atomic diffusion (Numakura et al. 1998) to evaluate the diffusion coefficient of Al in Ni3Al for various compositions.