Diffusion of Aluminum, Magnesium, Silicon, and Zirconium in Nickel

The diffusion rates of aluminum, magnesium, silicon, and zirconium, alloyed as single additives in nickel, have been measured at temperatures between 800°C and 970°C. The method consisted of measuring the weight gain caused by surface oxidation of the additive in a wet hydrogen ambient. The surface oxides were identified by electron diffraction. Grain size was about 0.05 mm in Al–Ni, Si–Ni, and Mg–Ni but less than 10−3 mm in Zr–Ni. The composite volume and grain boundary diffusion coefficients are given by DAi→Ni = 1.1 exp(−59 500/RT); DMg→Ni = 2.3×10−5 exp(−31 300/RT); DZi→Ni = 10.6 exp(−64 800/RT); DZr→Ni = 1×10−5 exp(−26 700/RT). Stereo and photomicrographs indicate considerable grain boundary diffusion, particularly in Mg–Ni and Zr–Ni.