Numerical relationships in binary metallic systems

The equilibrium diagrams of a family of binary alloys such as those of copper or silver with zinc, aluminium, or tin at first sight appear to be extraordinarily similar, but all efforts to predict quantitatively the silver-zinc diagram, for example, from a knowledge of the copper-zinc series and the properties of the silver, copper, and zinc atoms have failed. In this paper, certain relationships which are believed to exist in binary metallic systems are pointed out. There is also evidence, which is not now brought forward, to show that these relationships may also be found in binary systems of other types. If these simple relationships can be established, it will be at least a step towards the solution of the larger problem. When a metal is added to copper, silver, or gold, it often forms a primary solid solution with the solvent element. On the addition of more of the solute, a two-phase range is reached, then a second or β-solid solution, range, them a secondary or γ-solid solution, after which the phase relationships often become extremely complicated. The relevant portion of the copper-aluminium series is shown in fig. 1.