Microstructures of mechanically alloyed Fe60Ni40 studied by XAFS and XRD

The structures of the mechanically alloyed Fe60Ni40 powders are investigated by X-ray absorption fine structure (XAFS) and X-ray diffraction (XRD). For the Fe60Ni40 mixture milled for longer than 10 h, the XRD patterns indicate that the bcc phase of α-Fe almost disappears and only the fcc phase remains. The XAFS results further demonstrate that the local structure of Fe atoms is similar to that of Ni atoms for the MA Fe60Ni40 (10 h) alloy. With the milling time going to 40 h, the first-shell bond length R1 = 2.48 Å, coordination number N1 = 11.9 and Debye–Waller factor σ = 0.117 Å around Fe atoms are nearly equal to those (R1 = 2.49 Å, N1 = 12.0 and σ = 0.117 Å) around Ni atoms and the magnitude peaks of the higher shells disappear. These results imply that the local structure of Fe atoms is identical with that around Ni atoms in the MA Fe60Ni40 (40 h) alloy, where a homogenous solid solution with a large lattice distortion is produced as a final product of MA.