Structural Analyses of the β and γ Alloys of Al-Mg

Abstract

The atomic positions of the β and γ phases of Al-Mg alloys are determined, and the kinds of atoms corresponding to them are assigned by taking account of the difference of atomic radii between Al and Mg. The structure of the β phase is cubic with a unit cell containing 108 atoms. The space group, the lattice parameter and the average coordination numbers are Pm3m, 12.419 Å and 12 respectively. The structure is a superstructure of fundamental f.c.c. arrangement. The observed satellite spots are essentially explained by the displacement of atoms from average positions. The structure of the γ phase is cubic with a unit cell containing 54 atoms. The space group is Im3m, and the lattice parameter is 10.437 Å. The structure is a superstructure of fundamental b.c.c. arrangement.