Effect of Hydrostatic Pressure on Self-Diffusion in Gold-34 Atomic Percent Silver Alloy

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Abstract
The diffusion of 110Ag and 198Au in a nominally Au‐34 at.% Ag alloy has been measured at 860°, 910°, and 960°C and at hydrostatic pressures from 2070 to 8280 bars. A retarding effect of pressure on the diffusion rate has been observed for both the silver and gold tracers. Temperature determination, uniformity, and reproducibility have been found to be the limiting sources of error in pressure‐diffusion studies. Activation volumes are 7.2 cm3 per mole for 110Ag and 7.5 cm3 per mole for 198Au, consistent with the theory of Lawson, Rice, Corneliussen, and Nachtrieb, and with the experimental value of the activation volume of motion of vacancies ΔVm in Au found by Emrick. Changes in activation enthalpy values and frequency factors have been calculated and compared to the experimentally determined values‐the agreement is fair. The variation of diffusion rates and activation volumes is explained on the basis of isothermal compressibilities where Ag is much more compressible than Au.

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