Diffusion of Iron, Cobalt, and Nickel in Single Crystals of Pure Copper

Abstract

The rates of diffusion of radioactive tracers of Fe, Co, and Ni in single crystals of pure copper have been measured as a function of temperature from about 700 to 1075\ifmmode^\circ\else\textdegree\fi{}C. The results, obtained by the tracer-sectioning technique, are as follows: ${D}_{\mathrm{Fe}\ensuremath{\rightarrow}\mathrm{Cu}}=1.4\mathrm{exp}(\ensuremath{-}\frac{51 800}{\mathrm{RT}}); {D}_{\mathrm{Co}\ensuremath{\rightarrow}\mathrm{Cu}}=1.93\mathrm{exp}(\ensuremath{-}\frac{54 100}{\mathrm{RT}}); {D}_{\mathrm{Ni}\ensuremath{\rightarrow}\mathrm{Cu}}=2.7\mathrm{exp}(\ensuremath{-}\frac{56 500}{\mathrm{RT}});$ all in units of ${\mathrm{cm}}^{2}$/sec. An exploratory measurement for a Mn tracer in copper was made at 1069\ifmmode^\circ\else\textdegree\fi{}C with the result $D=1.49\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ ${\mathrm{cm}}^{2}$/sec.The results of several current theoretical calculations are compared with the present data: Wert and Zener's correlation of ${D}_{0}$ and $Q$ is supported by the present work; the basic qualitative prediction of Lazarus' screening theory is borne out by the present results, although the extent of the detailed agreement is not clear at this time. The experimental data yielded unexpectedly large diffusion coefficients at low temperatures in some cases and several possible causes are considered. Finally, a new experimental method is described for determining diffusion coefficients with tracers emitting only very low-energy particles.