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

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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 ballmilled Cu_Fe_(12-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 ballmilling process.
© 1996 The American Physical Society. The authors express their appreciation to Dr. Kristl Hathaway (NRL) for valuable discussions concerning the magnetic and electronic properties of the Fe-Cu and Fe/Cu systems, and to Professor J. J. Rehr and associates (University of Washington) for providing us with the theoretical EXAFS simulation (i.e., FEFF) codes used here. This research was carried out in part at the National Synchrotron Light Source (Brookhaven National Laboratories, Upton, New York), which is sponsored by the U.S. Department of Energy. In addition, some of the samples included in this research were processed and characterized with support from the Spanish CICYT through projects Mat. 92-0491 and Mat. 92-0404. A.H. acknowledges support to the BBV Foundation and K.M.K. acknowledges support of the National Research Council during the time of this research.