Dilute solutions of aluminium in gold

Abstract

The paper deals with the solid condition of alloys containing not more than 5 per cent. by weight of aluminium. The diagram is a concentration temperature diagram, the atomic percentage of aluminium being measured horizontally from left to right, and the temperature, in degrees Centigrade, being measured vertically. The alloys melt at varying temperatures, but below the upper line Aa bcd of the diagram they are wholly solid; we may say, approximately, that they are wholly solid below 525ºC. Between this temperature and the level of the point L there is a range of 100º. The diagram shows four compartments in this area and records the following facts:-The first area, on the left, indicates the fact that gold can dissolve rather more than 2 per cent. by weight of aluminium to form uniform solid solutions; these we call α . with rather more aluminium we have the complex alloys of the second area, containing, in addition to α , a second constituent β , In the alloys of the third compartment, β is the sole constituent, while in the fourth a new constituent D appears. Like α, β can very in composition, but only between narrow limits; D is probably the compound Au 5 Al 2 .