Mössbauer and X-Ray Diffraction Study of the Phase and Structure Transformations During Annealing of Mechanically Alloyed Al₆₅Cu₂₃Fe₁₂

Abstract

A powder mixture of Al₆₅Cu₂₃Fe₁₂ composition milled for four hours in a planetary ball mill was used as a starting material for quasicrystalline structure formation. Phase analysis of as-milled samples shows a mixture of intermetallic phases with preponderance of A2 and DO₃ structures. Also the presence of residual Al and Fe was detected. Annealing the milled samples gives rise to complex solid-state transformations. Mössbauer spectroscopy shows that the residual Fe amount decreases gradually with annealing temperature and that starting from the temperature of 440†C only an asymmetrical doublet is present. The formation of a structure almost totally icosahedral was observed in the XRD patterns of samples annealed at 600†C and above. The qualitative differences in the Mössbauer spectra observed for these samples may be associated with the presence of “approximant” phases to quasicrystalline structure.