Application of mechanical spectroscopy to studies of atomic diffusion in ordered compounds

An example of useful application of mechanical spectroscopy to diffusion measurements is presented. A thermally activated anelastic relaxation effect has been observed in Ni3Ga, an intermetallic compound of the L12 structure. The relaxation is of similar nature to that reported for Ni3Al [H. Numakura, K. Nishi, Mater. Sci. Eng. A 442 (2006) 59–62], and is attributed to stress-induced reorientation of Ga atoms in the Ni sublattice. By assuming the diffusion mechanism proposed for these compounds [H. Numakura, T. Ikeda, M. Koiwa, A. Almazouzi, Phil. Mag. A 77 (1998) 887–909], the diffusion coefficient of Ga has been evaluated from the relaxation rate. It agrees fairly well with the extrapolation of the high-temperature data of the tracer diffusion coefficient in the literature.