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 10⁶ 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×{}10⁸. A precise fit to all the data requires a slight upward curvature. In the temperature range studied here, we obtain $Q=45$, 750±{}750 cal/mole and D₀=0.104±0.06 cm²/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.