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Effect of Gradient Energy on Diffusion in Gold‐Silver Alloys

 

作者: H. E. Cook,   J. E. Hilliard,  

 

期刊: Journal of Applied Physics  (AIP Available online 1969)
卷期: Volume 40, issue 5  

页码: 2191-2198

 

ISSN:0021-8979

 

年代: 1969

 

DOI:10.1063/1.1657957

 

出版商: AIP

 

数据来源: AIP

 

摘要:

Interdiffusion coefficients have been measured in Au&sngbnd;Ag alloys containing 18–50 at.% Au at temperatures from 200° to 260°C and over very short penetration distances (7–35 Å). The diffusivities were determined from the rate of decay of composition modulations in vapor‐deposited films. The wavelength and amplitude of the modulations were measured by x‐ray diffraction. From the dependence of the diffusion coefficient on the wavelength of the composition modulation, it was established that it is necessary (as proposed by Hillert and by Cahn) to allow for the effect of the ``gradient energy'' on the driving force when diffusion occurs in the presence of very sharp composition gradients. The observed gradient‐energy coefficient wasK=−(2.6±0.5)×10−6erg·cm−1in agreement with a value calculated on the basis of nearest‐neighbor interactions. The interdiffusion coefficients (corrected to an infinite penetration distance) were in good agreement with an extrapolation of existing high‐temperature data obtained with conventional diffusion specimens, thus demonstrating that the vapor‐deposited film technique is capable of determining, with good precision, diffusivities of the order of 10−20cm2sec−1. This is some eight orders of magnitude smaller than those that can be measured conventionally.

 

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