The structure of γ-brass

Westgren and Phragmén have recently described the results of investigations on the structures of Cu-Zn, Ag-Zn and Au-Zn alloys. As a result X-ray analysis by the powder method, five different types of structure were found in the case of the Cu-Zn alloys. Structures were successfully assigned to four of these phases, but in the case of the γ-phase a complete elucidation was not attempted. The structure is cubic, and contains 52 atoms to the unit cube. The following table is taken from Westgren and Phragmén's paper:- Further information was obtained from examination of single crystals of a γ Cu-Zn alloy. Laue photograms and rotation photograms were both used for this purpose. By way of conjecture, Westgren and Phragmén suggested the formulæ Cu4Zn9, Ag4Zn9, abd Au4Zn9, as these correspond to compositions coinciding with one of the homogeneous γ-phase ranges. We have found that these formulæ are incorrect, the true formulæ being Cu5Zn8, Ag5Zn8, and Au5Zn8.