Diffusion Measurements in the System Cu-Au by Elastic Scattering

Abstract

A broad-range magnetic spectrograph has been used to study the diffusion of gold into copper in the temperature range 360-500\ifmmode^\circ\else\textdegree\fi{}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\ifmmode\times\else\texttimes\fi{}${10}^{8}$. A precise fit to all the data requires a slight upward curvature. In the temperature range studied here, we obtain $Q=45$, 750\ifmmode\pm\else\textpm\fi{}750 cal/mole and ${D}_{0}=0.104\ifmmode\pm\else\textpm\fi{}0.06$ ${\mathrm{cm}}^{2}$/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.