Nanostructuration of i-Al64Cu23Fe13 quasicrystals produced by arc-furnace

Abstract

The Al 46 Cu 23 Fe 13 quasicrystal phase, prepared by arc-melting and nanostructured using high energy ball milling technique, was studied employing X-ray diffraction, transmission electron microscopy, ferromagnetic resonance and electric transport measurements. Fe local environments were studied by Mössbauer spectroscopy. The resistivity ratio R(4.2 K)/R(300 K) is within the expected values commonly observed in an icosahedral phase. In general, the experimental results show that an appropriate heat treatment of the as-cast alloy prepared by arc-melting makes possible to obtain good quasicrystal samples. On the other hand, for milling time longer than five hours, the average grain-size of quasicrystal phase reduces, but it preserves Fe local atomic orders. It is also observed that the quasicrystalline sample decomposes in an iron rich nano-quasicrystalline phase and a ε-Al 2 Cu 3 phase. Electric transport measurements show that at low temperatures the nanoquasicrystalline samples behave strongly different to their solid counterparts, an effect attributed to a long-range order reduction and an increasing of grain boundary regions. The presence of local magnetic moments in the nanostructured sample is also discussed.

Influence of high energy milling on the microstructure and magnetic properties of the Al–Cu–Fe phases: the case of the i-Al64Cu23Fe13quasicrystalline and the ω-Al70Cu20Fe10crystalline phases

“…The average isomer shi hdi and quadrupole splitting hDi values tted for 0 h samples are in good agreement with those reported in the literature. 8,20 Comparing Fig. 2(b) and (d) for 0 h milling, we can note the differences in the spectra for the i-phase and u-phase.…”

“…Samples of Al-Cu-Fe alloys, quasicrystalline i-Al 64 Cu 23 Fe 13 and crystalline u-Al 70 Cu 20 Fe 10 phases, have been prepared following previous works. [18][19][20] First, to obtain the solid sample high-purity elements of Al (99.999%), Fe (99.5%) and Cu (99.9%) were melted in an arc furnace (the ingots were re-melted several times to ensure homogeneity). Subsequently, the solid samples (previously settled in a quartz tube under argon atmosphere) were annealed at 700 C and 600 C to obtain the quasicrystalline and crystalline phase, respectively.…”