Diffusion Measurements in the System Cu-Au by Elastic Scattering

A broad-range magnetic spectrograph has been used to study the diffusion of gold into copper in the temperature range 360-500°C by elastic scattering of protons and deuterons. This is a new technique in solid diffusion measurements and should have fairly wide applicability in intermetallic diffusion. This investigation extends the data a factor of ${10}^6$ below the sectioning range. These results together with data of sectioning observers, show the Arrhenius law to be approximately valid over a range in $D$ of 5×${10}^8$. A precise fit to all the data requires a slight upward curvature. In the temperature range studied here, we obtain $Q=45\mathrm{}$, 750±750 cal/mole and $D_0=0.104\mathrm{}\pm 0.06$ ${\mathrm{cm}}^2$/sec. This represents a decrease of about 4000 cal/mole from the most precise data in the sectioning range. This curvature is attributed to diffusion along internal surfaces, although the possibility of multiple diffusion mechanisms still remains.