Mössbauer investigations of mechanical alloying in the Fe-Cu system

Abstract

A fcc-Fe50Cu50 solid solution was prepared by mechanical alloying of elemental Fe and Cu powder blends. The alloying process was studied by using x-ray diffraction and Mössbauer spectroscopy. Initially, the milling process reduced the crystallite sizes of both elemental powders. After 20 h milling, some Fe particles transformed into the fcc structure. Due to the structural similarity of the fcc-Fe and fcc-Cu phases, composites consisting of coherent Cu and Fe regions were formed. The increasing density of interfaces during further milling resulted in an interdiffusion of Cu and Fe. The alloying process was monitored by Mössbauer investigations which showed an increasing Fe concentration in fcc Cu. After 50 h of milling, the Mössbauer spectra consisted of a broadened sextet caused by a hyperfine field distribution, which demonstrates that the Fe and Cu were alloyed on an atomic level. These observations are in agreement with a model proposed by C. Gente, M. Oehring, and R. Bormann [Phys. Rev. B 48, 13244 (1993)] describing the formation of unstable alloys by mechanical alloying.