Structural Studies on Ribbons of Al-Fe-Mischmetal Alloys

D. RODRIGUEZ; F. AUDEBERT; B. ARCONDO; H. SIRKIN

Ouro Preto

Simposio; 4º Brazilian Symposium on Glasses and Related Materials; 1999

Al-based alloys are widely used in industry, since the development of high strength Al-based alloys is very important. Rapid solidification is an effective way to get supersaturated solid solution, metastable compounds and amorphous phases. The Al-TM-RE (TM: Transition Metal, RE: Rare Earth) amorphous alloys with good mechanical properties were found in 1988. It is known that some amorphous Al-alloys present ductile behaviour while other are very brittle. Some authors propose that this brittle behaviour is a consequence of a short range order similar to that of icosahedral phase. In this work ribbons of Al-Fe-Mm (Mischmetal: mixture of rare earth) were produced with 85 to 90 at% of Al. Amorphous and partially amorphous samples were obtained. The structure was studied means of Mössbauer spectrometry and X-ray diffraction technique with Cu radiation in a - goniometer. Mössbauer spectra were obtained at room temperature with a 57Co(Rh) source in transmission geometry. The spectra of the amorphous were fitted employing a histogram distribution of electric field gradient with a linear dependence of the isomer shift (IS) on the quadrupole splitting (QS). In any case, the QS distribution curves present two or more local maxima and a non zero probability for QS=0 being the peak values of QS rather independent of composition. The IS distributions result very sharp. The mechanical behaviour was qualified by means of a simple hand bending test and Vickers microhardness. The structure of the amorphous is compared with the structure reported of other Al amorphous and quasicrystalline alloys, and is also compared with the corresponding crystalline sample.