Mössbauer effect studies of mechanical alloying and grinding

A.F. CABRERA, M.B. FERNÁNDEZ VAN RAAP, M. MEYER, C. RODRÍGUEZ TORRES, F. H. SÁNCHEZ, L. MENDOZA ZÉLIS.

MATERIALS TRANSACTIONS

JAPAN INST METALS

Año: 1995 vol. 36 p. 357 - 364

1345-9678

Mössbauer effect studies of mechanical alloying and mechanical grinding of Fe-B, Fe-Sn and Fe-TM-Al (TM=Ni, Cu), complemented by X-ray diffraction analysis are presented. Some of these Systems (Fe-Sn) are especially suitable for this type of research because the environments of both elements can be probed. In all cases powders were processed with a Restch MM2 horizontal vibratory mill under argon atmosphere.  In Fe1-xSnx (0.15£x£0.40), the evolution of mechanical alloying with time and the dependence of the stationary state with composition fluctuations were inferred from Mössbauer spectra. Solubility of tin into bcc iron was found to be extended up to a maximum of about 22 at. %.  Pure powder mixtures of nominal composition Al75Ni120Fe15 and Al63Cu25Fe12 have been mechanically alloyed. Stable disordered crystalline phases were obtained alter milling and, in some cases, the partial ordering of bcc structures induced by milling was observed. Further annealing did not produce structural changes but removed the remaining disorder. The characteristic quadrupole interaction parameters were obtained by Mössbauer spectroscopy. The evolution of Fe2B with grinding time was studied. The first milling stage was characterized by fragmentations and accumulation of strain. On further processing, segregations of a-Fe occurred while grain size reduction continued and strain was partially removed. For Langer grinding times separation of   a-Fe proceeded at an almost steady rate. Two additional experiments designed to reduce and increase oxygen contamination let us tentatively discard this element as the main responsible for the observed decomposition.