Diffusional jumps of intrinsic atomic defects in ordered alloys observed through anelastic relaxation effects

Detailed measurements of the anelastic relaxation effect of Ni3Al at intermediate temperatures have been carried out by isothermal mechanical spectroscopy at low frequencies. The results confirm the proposed mechanism that the effect is due to stress-induced reorientation of antisite Al atoms in the Ni sublattice [Numakura et al. (1999)]. The diffusion coefficient of Al has been evaluated from the relaxation rates obtained in the measurements by assuming the a sublattice vacancy mechanism. The values appear to be consistent with the estimates from measurements of chemical diffusion at high temperatures. The utility of this effect as a means of measuring the elementary process of diffusion in solids of the L1(2) and related structures is discussed.