Compositional dependence of quasicrystal formation in mechanically alloyed AlCuMn

Abstract

Quasicrystalline AlCuMn powders have been prepared by mechanical alloying from crystalline elemental powders. The composition range of the quasicrystalline phase has been determined by X-ray diffraction. Single-phase quasicrystalline material forms in the ranges 15-25 at.% Cu and 10-20 at.% Mn. In addition, a twophase region of quasicrystalline phase and "solid solution" exists for 30 at.% Cu and 5-10 at.% Mn, and a mixture of quasicrystalline material and pure copper shows up for Al70Cu25Mn5. Alloys with low aluminium content exhibit a single-phase "solid solution", and for aluminium-rich compositions the "solid solution" coexists with the pure elements. Crystallization temperatures, crystallization enthalpies and lattice parameters, obtained from X-ray diffraction investigations, are compared with the data obtained for rapidly quenched samples. Conclusions on the stability of the powders are drawn from these results. © 1990.