Investigation of Equilibrium Diagrams of Ternary Alloys by X-Rays

Abstract

IT is the purpose of this note to point out how rapidly and efficiently ternary equilibrium diagrams may be elucidated by means of X-ray analysis. In a recent paper, Jette1 described a partial analysis of the chromium-iron-silicon system by X-rays. We have carried out the analysis of several ternary diagrams which will be published shortly. As an example, we give the diagram for the copper-nickel-aluminium system, the compositions being represented in the usual way by points within an equilateral triangle. Any one such diagram shows the phases at a given temperature, and a series of such diagrams is required to represent the state of affairs at different temperatures. The present diagram actually shows the phases present after a uniform heat treatment of slow cooling at 10° C. per hour. No claim is made that equilibrium has been established, our main object being to show the exploratory power of X-ray analysis. It will be supposed that the binary equilibrium diagrams, represented by the three sides of the triangle, have previously been established by metallurgical or X-ray methods. It is our experience that the investigation of the whole interior of the ternary diagram is, in general, easier than that of a single complicated binary system, since for the most part the phases are the same as those of the binaries. In other words, the appearance of quite a new phase is comparatively rare ; we merely have to determine how far the two-component phases extend into areas of the ternary diagram.