The relation between mean atomic volume and composition in copper-zinc alloys

Abstract

A great deal of work has been done by X-ray methods on the relation between atomic volume and composition in alloy systems, but a large portion of the data so far recorded has not been determined with the high precision attainable by present methods of analysis. This paper contains the results of precision measurements on copper-zinc alloys covering the whole range of composition from one end of the equilibrium diagram to the other. Previous work in this field covers several binary systems. Vegard and his co-workers examined the alkali halides, the copper-nickel and other alloys, and found that generally the lattice dimensions change linearly with the composition. The gold-copper system did not follow this rule; this was confirmed later by van Arkel and Basart, who deduced from their observations that the fifth exponent of the atomic "diameter” was more suitable than the first as an additive quantity. Westgren and his collaborators also measured the lattice dimensions of a number of binary alloy systems. They found that a marked contraction takes place in all cases where chemically unrelated metals are alloyed with each other, the contraction being too pronounced to make the linear dimensions additive. In a paper on the silver-cadmium alloy systems, by Astrand and Westgren, the change in atomic volume with composition is traced through all the pure phases α, β, γ, and η of that system. The discontinuities between the phases are but slightly marked; this is taken to indicate that in this system the atoms occupy approximately the same space, whatever their grouping may be. Owen and Preston, in a study of the copper-zinc system, tentatively took a smooth curve through the determined atomic volumes for various compositions. They found a marked contraction in atomic volume.