Materials Science Forum, Vol.360-3, 155-160, 2001
Short range order study in Al-Fe-X melt spun alloys
The ductility and stability of the aluminium-based amorphous alloys are very dependent on the components and its concentration. The X-ray diffractograms of many amorphous AI-Fe-X alloys show a prepeak attributed to a strong chemical short range order. It is known the strong atomic interaction between Al and Fe atoms and, as a consequence Al-Fe associations are formed in the melt of the Al-Fe-X alloys. These associations, and its interaction with the third element (X), have a strong effect both on the glass forming ability and on the atomic structure of the alloy, which is responsible of the stability and mechanical properties of the material. The structure of the associations is not known up to date. In some cases, with X being early transition metals, it was suggested that the third element stabilised an icosahedral local order around the Fe atoms. Then, the structure of these alloys may be considered as a heterogeneous amorphous, composed with clusters embedded in a rich aluminium matrix [1]. Meanwhile, in other ternary systems, Al-Fe-RE (RE: Rare Earth), it was proposed that the RE element is randomly distributed in an Al- rich amorphous matrix [2]. With the aim to contribute to the knowledge of the short range order in the Al-Fe-X amorphous alloys, we analyse the Fe environments in three different systems with X= Nb, Sb and Mm (Misch metal: solid solution of RE), on rapidly quenched melt spun ribbons. The structure was analysed by means of X-ray diffraction and Mossbauer spectrometry at room temperature with a Co-57(Rh) source in transmission geometry. The local order in the amorphous structure is discussed and compared with those of quasicrystalline and crystalline phases.