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

Abstract

Extended x-ray-absorption fine-structure ͑EXAFS͒ 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 x Fe 1Ϫx samples ͑xϭ0.50 and 0.70͒. 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. ͓S0163-1829͑96͒10033-3͔

Local atomic structure in iron copper binary alloys: An extended X-ray absorption fine structure study

“…1(b) have been corrected for electron phase shifts using the first shell-path from FEFF and therefore, the FT peaks should correspond directly with the true bond distances of the near neighbours. Results of the first coordination shell fitting parameters obtained are: an Fe-Fe coordination number of 7.9 ± 0.3 at a distance 0.248 ± 0.002 nm, r 2 = (41 ± 5) · 10 À4 Å 2 and DE 0 = 7.16 eV; whereas the corresponding values for the second shell are N = 6.2 ± 0.2, R = 0.285 ± 0.002 nm, r 2 = (48 ± 5) · 10 À4 Å 2 and DE 0 = 7.16 eV; in agreement with the parameters known in the literature [24]. The estimated errors are the standard ones for EXAFS.…”

Mechanical Alloying of Fe-Cu Alloys from As-Received and Premilled Elemental Powder Mixtures

“…In spite of the larger atomic size of copper when compared to iron, the fcc Cu lattice is expanded by the incorporation of iron atoms in agreement with previous works [1][2][3]. Harris et al [7] propose a model in which the strong interaction between like atom pairs (Fe-Fe, Cu-Cu) provides Coulombic forces which establish geometrical limitations prohibiting the unlike Fe-Cu pairs from coming any closer than the measured distances. In fact, the dilated bonds measured between Cu and Fe indicate that either a very weak interaction or a repulsion exists between unlike neighbours as a result of a positive heat of mixing in this system [9].…”

Neutron induced damage in reactor pressure vessel steel: An X-ray absorption fine structure study

“…In our analysis, Kedges final-state potentials for the central atoms (i.e., Cu, Ni or Mn) were calculated using atomic clusters derived from the known atomic coordinates of body-centered-cubic (bcc) phase Fe structures as referred in Refs. [23,24].…”