X-ray study of the inter-diffusion of copper and zinc

Abstract

Since the publication of Roberts-Austen's classical paper describing extensive investigations on the inter-diffusion of metals and alloys, several methods have been employed to study the phenomenon. A comprehensive survey of these has recently been published by Hevesy and Seith. Only a few investigations have been recorded in which X-ray analysis has been applied to the problem, as it is only during the last few years that X-ray measurements and technique have attained the necessary precision to enable the phenomenon to be examined by this method. The present paper describes an attempt to develop the X-ray method for the investigation of the phenomenon of inter-diffusion in metals. When a mixture of silver and zinc filings, or copper and zinc filings is heated in vacuo , inter-diffusion takes place. The heated mixture, when cool, can be broken up and then used to produce X-ray reflections in the precision camera. In the photographs, the reflection lines from each phase present in the sample are usually well separated and can be studied independently, so that the composition of each phase can be determined from standard parameter-composition curves. The method therefore provides a means of studying any change which occurs in the composition of each phase with time and with change of temperature, and thus it differs from such methods as chemical analysis, zone measurements or electrical resistance, where usually a mean effect is measured. Since 0·01 mm of copper absorbs about 36% of the K α radiation from copper, the reflected beams registered on the photographic film are produced by the surface layers of the particles, so that as diffusion proceeds, the photographs indicate the changing conditions in the outermost layers only.