Effect of Pressure on the Interstitial Diffusion of Nickel in Lead to 50 kbar

The diffusion of nickel in lead has been investigated using radioactive-tracer and sectioning techniques for pressures of up to 50 kbar and for temperatures in the range 208-591 ^∘{}C. The data were analyzed assuming a single effective mechanism of diffusion with a temperature- and pressure-dependent activation energy and preexponential factor. The activation energy and volume at the melting temperature and atmospheric pressure are, respectively, ΔH=10.6±0.4 kcal/mole and ΔVV₀=0.13±0.04. The pressure and temperature coefficients of the activation volume, although quite uncertain, were also determined. The small activation energy and volume indicate that nickel diffuses in lead primarily by the interstitial mechanism.