Preparation and analysis of quasicrystalline phases by high energy ball milling and X-ray diffraction

The consequences of solid-state reactions in mechanically alloyed Al-Cu-Fe powders were studied using advanced techniques of X-ray diffraction pattern interpretation. A set of intermetallic phases was identified which appeared as a result of mechanical alloying and subsequent annealing. These intermetallics were the intermediate products formed during to gradual mechanical and thermal homogenization and excitation. The quantitative phase composition of mechanically alloyed powders was determined using interactively controlled database phase analysis, fitting procedures and modelling of X-ray patterns for different structures. The analysis allowed us to optimize the processing route, and identify the conditions promoting the formation of single phase quasicrystalline powder. Single phase powders of the quasicrystalline Al6Cu2Fe intermetallic (ψ-phase) were obtained from the mixture of elemental powders Al70Cu20.3Fe9.7 after a short time milling and annealing at 800 °C under argon

Crystallochemical aspects of solid state reactions in mechanically alloyed Al-Cu-Fe quasicrystalline powders

A number of elemental mixtures having initial compositions close to Al65Cu23Fe12 were mechanically alloyed at different energy intensities using a planetary mill. Laboratory X-ray diffraction analysis, differential scanning calorimetry and Mössbauer spectroscopy were used for characterization of the phase and structural state of mechanically alloyed powders after different periods of milling and annealing. Several exothermic effects were found, and these were ascribed to specific solid-state reactions. Quantitative phase analysis was applied in order to identify the mechanism of solid-state reactions taking place in the vicinity of the quasicrystalline phase domain in the Al-Cu-Fe system as a result of mechanical and thermal excitation and homogenization. Metastable intermetallics were identified which possess certain structural and topological elements identical to those found in quasicrystals. © 2001 Acta Materialia Inc. Published by Elsevier Science Ltd