Near-neighbor mixing and bond dilation in mechanically alloyed Cu-Fe

Abstract

Extended x-ray-absorption fine-structure (EXAFS) measurements were used to obtain element-specific, structural, and chemical information of the local environments around Cu and Fe atoms in high-energy ball-milled ${\mathrm{Cu}}_{\mathit{x}}$ ${\mathrm{Fe}}_{1\mathrm{-}\mathit{x}}$ samples (x=0.50 and 0.70). Analysis of the EXAFS data shows both Fe and Cu atoms reside in face-centered-cubic sites where the first coordination sphere consists of a mixture of Fe and Cu atoms in a ratio which reflects the as-prepared stoichiometry. The measured bond distances indicate a dilation in the bonds between unlike neighbors which accounts for the lattice expansion measured by x-ray diffraction. These results indicate that metastable alloys having a positive heat of mixing can be prepared via the high-energy ball-milling process. © 1996 The American Physical Society.