Abstract
Using transmission electron microscopy and X-ray diffraction, we established that the ordered η1-Al50Cu44Fe6 and φ-Al47.5Cu49.5Fe3 (Fmm2) alloys with nano-sized domain structure are formed by slowly cooling, whereas β-solid solutions with a short-range order were found in quenched states. The φ′-modification which exhibits the additional long-period superstructure was also observed in Al47.5Cu49.5Fe3. The studies of low temperature magnetic susceptibility and heat capacity did not reveal any another phase transitions in these alloys. The indentation test showed that hardness and Young’s modulus consistently grow as β-Al50Cu33Fe17 → η1-Al50Cu44Fe6 → (φ+φ′)-Al47.5Cu49.5Fe3 and approach to those in icosahedral phase. The same trend in the Young’s modulus was obtained for alloys containing β-solid solution with a short-range order. Ab initio calculations, however, predicted the opposite tendency in cubic β-Al50Cu50−xFex with a decrease in x, which was explained by the weakening of the covalent Fe 3d – Al sp bonding. This discrepancy between the results for β- and ordered phases, we related to a crucial effect of ordering which is accompanied by a progressive distortion of cubic local structure in the series β-Al50Cu33Fe17 → η1-Al50Cu44Fe6 → φ-Al47.5Cu49.5Fe3. As we demonstrated for η-Al(Cu, Fe), these distortions lead to the strengthening of the both covalent Fe–Al and Cu–Al bonds and the higher modules.
Published Version
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