The diffusion of 63Ni was measured in pure and boron-doped polycrystalline Ni3Al as a function of temperature (692 to 1352C), A1 concentration (24 to 26at%Al), and boron content (0 to 500wt[ppm]). The volume and grain-boundary diffusion of 60Co and 68Ge were also measured in pure Ni3Al. Conventional grinding and ion beam sputtering techniques were used for the determination of the concentration profiles. The diffusivity of Ni, DNi*, was independent of the Al content above 1000C, indicating that antisite defects prevailed on both sides of stoichiometry. However, DNi* exhibited a minimum at the stoichiometric composition below 1000C, and this trend became clearer with decreasing temperature. The diffusivities of 60Co and 68Ge were also independent of the Al concentration between 880 and 1200C, but their grain-boundary diffusion depended upon the Al concentration. The addition of boron increased DNi* linearly above 1000C, but at lower temperatures, DNi*, in off-stoichiometric compositions decreased to the value for stoichiometric Ni3Al upon the addition of 100wt[ppm] boron, and then increased as above with further additions of boron up to ~500wt[ppm].

Tracer Diffusion in Pure and Boron-Doped Ni3Al. Hoshino, K., Rothman, S.J., Averback, R.S.: Acta Metallurgica, 1988, 36[5], 1271-9

Table 8

Diffusivity of Co, Cr, and Ti in Ni3Al

Table 8 (continued)

Diffusivity of Co, Cr, and Ti in Ni3Al