Effect of high pressure torsion at different temperatures on the local atomic structure of amorphous Fe-Ni-B alloys

摘要

The effect of the deformation temperature (293 and 77 K) by high-pressure torsion (HPT) on the atomic structure of melt-quenched amorphous Fe83-xNixB17 alloys (x = 25, 29, 33) and their crystallization thermal effect upon continuous heating have been analyzed by method of Extended X-Ray Absorption Fine Structure (EXAFS) in synchrotron radiation, transmission electron microscopy, and X-ray diffraction analysis. HPT at 293 K decreases the crystallization thermal effect, whereas HPT at 77 K increases it regardless of the alloy composition. The observed effect is caused by the reversibility of the structural transformations in the alloys upon variation in the deformation temperature. According to the results of the structure examination, HPT at 293 K leads to the formation of more ordered state (partially crystallized) of the initial amorphous alloys. On the contrary, HPT at 77 K stimulates the formation of more disordered amorphous structure (by destruction of short-range order and an increase in the average values of the coordination numbers around the iron atoms in the first coordination sphere). (C) 2017 Elsevier Ltd. All rights reserved.