X-ray powder diffraction and Moessbauer study of nanocrystalline Fe-Al prepared by mechanical alloying
- Istituto Nazionale per la Fisica della Materia, Venezia (Italy). Dept. di Chimica Fisica
- Istituto Nazionale per la Fisica della Materia, Padova (Italy). Dept. di Ingegneria Meccanica
- Istituto Nazionale per la Fisica della Materia, Bologna (Italy). Dept. di Fisica
Iron-aluminium alloys of composition Fe{sub 50}Al{sub 50} and Fe{sub 75}Al{sub 25} were produced by mechanical alloying (MA) of the pure elemental powders. A structural refinement of X-ray powder data on the mechanically alloyed products according to the Rietveld method has detailed the progressive dissolution of aluminium into the lattice of {alpha}-iron as a function of MA time. With respect to pure iron, a volume expansion of {approx}3% is measured in both compositions mechanically alloyed for 32 h. In the iron and aluminium phases, the Debye-Waller static disorder increases as a function of MA time and the intrinsic shape of the peak profiles becomes predominantly Cauchy. These changes are accompanied by an increase in the average microstrain and by a reduction in the average crystallite size (which includes also the effect of dislocations). The Moessbauer spectra show that in the equiatomic case the initial sharp magnetic sextet of {alpha}-iron is progressively reduced and is replaced by a doublet, while for the Fe{sub 75}Al{sub 25} composition a broad magnetic sextet is eventually obtained. Thermal scans at 600 C of the specimens mechanically alloyed for 2, 4 and 8 h precipitate essentially the Al{sub 5}Fe{sub 2} phase. In the case of the Fe{sub 50}Al{sub 50} specimens, annealing of the powders mechanically alloyed for 16 and 32 h precipitates mainly the partially ordered FeAl intermetallic compound, while no ordering is obtained in the Fe{sub 75}Al{sub 25} case.
- OSTI ID:
- 367319
- Journal Information:
- Acta Materialia, Vol. 44, Issue 8; Other Information: PBD: Aug 1996
- Country of Publication:
- United States
- Language:
- English
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