Fe–Co–Al nanocomposites: impact of the method of alloying on the phase content
摘要
The real structure and microstructure of the products resulting from incomplete interaction of Fe–Co–Al powdered blends by mechanical alloying were studied by X-ray diffraction, Mössbauer spectroscopy, thermal analysis, electron microscopy and mapping. Such nanocomposites are promising precursors of ceramometal catalysts. Two types of powdered iron were used. Also, two types of alloying were applied: one-step and two-step methods. Dispersion of the initial iron powders was shown to have a minor effect on the phase composition of nanocomposites. A considerable impact is exerted by the method of mechanochemical treatment. The one-step treatment produces a multiphase mixture of α-Fe, Al, Co, Fe–Al intermetallic, and a solid solution of Al in α-Fe. In the two-step method, the first treatment step of the Fe + Co mixture results in the formation of the Fe(Co)x solid solution with variable composition (x ≥ 0) and defective iron. At the second step of (Fe + Co) + Al treatment, the Fe(Co)x solid solution inhibits the interaction of iron with aluminium. The method of alloying also influenced the thermal analysis data. A microstructural model of the nanocomposite particle was proposed to explain the inhibitory action of the solid solution.