COMPOSITIONAL DEPENDENCE OF QUASI-CRYSTAL FORMATION IN MECHANICALLY ALLOYED AL-CU-MN

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.