Microstructures of mechanically alloyed Fe60Ni40 studied by XAFS and XRD

The structures of mechanically alloying Fe60Ni40 milled for 5, 10, 20 and 40 hours were investigated by XAFS and XRD. The XRD patterns indicate that the alpha-Fe phase almost disappears and only the fcc phase remains after milling for 10 hours. The XAFS results further show that the RSF shape of Fe atoms is similar to that of Ni atoms for the MA Fe60Ni40 (10 h) alloy. The Debye-Waller factors sigma(1) of the Fe and Ni atoms in the MA Fe60Ni40 (10 h) increase from 0.071 and 0.091 angstrom to 0.102 and 0.105 angstrom, respectively. These results demonstrate that the local structure of most Fe atoms in the MA Fe60Ni40 (10 h) has changed from bcc structure to fcc one after milling for 10 hours. With the milling time going to 40 hours, the sigma(1) of both Fe and Ni atoms increase to about 0.117 angstrom, the R-1 = 2.48 angstrom and N-1 = 11.9 around Fe atoms are equal to R1 = 2.48 angstrom and N-1 = 11.9 around Ni atoms and the magnitude peaks of the higher shells disappear for MA Fe60Ni40 (40 h). These results imply that the changes of local structure around Fe atoms are identical with that around Ni atoms in MA Fe60Ni40 alloys. We consider that the MA Fe60Ni40 (40 h) alloy is a homogenous solid solution.