The Al-Mn decagonal phase 1. A re-evaluation of some diffraction effects 2. Relationship to crystalline phases

Abstract

From a quenched, melt-spun ribbon of a specimen of Al₇₆Mn₂₄, bulk composition, the decagonal phase and a closely related ‘Al₃Mn’ phase have been examined using analytical electron microscopic techniques. It is proposed that descriptions of the decagonal phase by analogy to an icosahedral axial system be abandoned and that a different six-axis system be adopted instead, and that the non-crystallographic space group previously proposed for the decagonal phase be changed to one containing glide planes. The ‘Al₃Mn’ phase is seen to be an extremely close relative of the Al-Mn decagonal phase. However, the state of knowledge about the ‘Al₃Mn’ structure is too poor to be of any use in improving the understanding of atomic arrangements in the Al-Mn decagonal phase.