LOCAL-STRUCTURE OF MECHANICALLY ALLOYED NANOCRYSTALLINE BCC FE80CU20 SOLID-SOLUTION

The fine structure of mechanically alloyed BCC Fe80Cu20 solid solution has been studied by X-ray diffraction (XRD), Mossbauer spectroscopy a nd the extended X-ray absorption fine structure (EXAFS) technique. The appearance of Mossbauer spectrum with a broad hyperfine magnetic fiel d distribution demonstrates that the alloying is at an atomic level an d complex forms of coordination exist in the solution. EXAFS results f urther prove the atomic alloying from the clear observation of Cu atom s taking on BCC coordination in the solution. Furthermore, a reduction in the nearest-neighbor coordination number of a center Cu atom but n ot for a center Fe atom due to surface effect and structure defects in dicates the composition nonuniformity that Cu atoms are rich at interf ace and Fe atoms are slightly rich in the core of a BCC nanocrystal.