Effect of Coherency Strains on Diffusion in Copper-Palladium Alloys

Abstract

Interdiffusion coefficients have been measured in Cu–Pd alloys containing 70–90 at.% Pd at temperatures from 355° to 440°C using films containing short wavelength composition modulations produced by evaporation. From the relative intensities of the high- and low-angle satellites about the 111 Bragg peak, it was established that the composition modulations were coherent for λ<28 Å (where λ is the wavelength of the modulation) and were incoherent for λ>38 Å. Over the range 28 to 38 Å, there was a progressive loss in coherency and this was accompanied by a twofold decrease in the diffusivity. This decrease confirms quantitatively the effect of coherency strains on diffusion predicted by Cahn. The dependence of the effective diffusion coefficient on wavelength in the coherent modulations yielded K=−10.3×10−6 erg·cm−1 for the gradient-energy coefficient.

Isothermal solid‐state transformation kinetics applied to Pd/Cu alloy membrane fabrication

“…Philofsky and Hilliard 35 found activation energies of 204 and 277 kJ/mol for Cu compositions of 20 and 5 wt %, respectively, between the temperatures of 355 and 440 C. The samples by Al-Kassab et al 34 consisted of sputter deposited layers of Pd and Cu of a total thickness of 20 nm. The reason that the low temperature data 34 yielded an activation energy corresponding to bulk diffusion at low temperatures was due to the very few grain boundaries present in the sample because of the method of deposition, thus producing bulk diffusion at a low temperature.…”

“…The reason that the low temperature data 34 yielded an activation energy corresponding to bulk diffusion at low temperatures was due to the very few grain boundaries present in the sample because of the method of deposition, thus producing bulk diffusion at a low temperature. The submicron films of Philofsky and Hilliard 35 contained short wavelength composition modulations produced by evaporation, upon which the interdiffusion coefficients were dependent. They theorized that extrapolating the wavelengths to infinity yielded true bulk diffusion coefficients at low temperatures.…”

Influence of depth resolution on interdiffusion measurements in polycrystalline Cu/Pd multilayers

“…Interdiffusion in the Cu/Pd structures was in the past the subject of investigations both in monocrystalline 16 …”

Strain Energy Effects in the Spinodal Decomposition of Cu-Ni(Fe) Nanolaminate Coatings

“…Single and multiple peaks in the interdiffusivity variation with wavenumber are reported [24,25,35] for the diffusion results of the Cu/Ni, Cu/Pd, Au/Cu, and Ag/Pd nanolaminate systems. The multiple fluctuations observed in both the amplification of Figure 3 and the interdiffusivity of Figure 4 are a potential consequence of: a shift towards longer wavelengths that can occur with aging time; and that strain energy will still enhance (outside the spinodal) or hinder (within the spinodal) diffusion at the shorter wavelengths.…”

“…In an assessment of the collective interdiffusion in both Fe-and Si-based nanolaminate structures [46], it has been proposed that a collective atomic jumping mechanism that governs interdiffusion involves at least 8-15 atoms. ) for the Cu/Ni(Fe) nanolaminates (open circles) along with experimental data for Cu0.877Ni0.107Fe0.016 (solid diamonds) [33] and Cu0.5Ni0.5−xFex (solid squares) [34,35].…”