Plasma-Induced γ-Fe Phase on S3A Alloy Ribbons

Amorphous alloy 2605S3A ribbons were exposed to cold plasmas of N2 and Ar-N2 at temperatures lower than Tx = 808 K. The X-ray diffraction patterns of the plasma treated ribbons, consist of a broad signal centered at 2θ = 45° characteristic of the amorphous state. The corresponding conversion X-ray Mossbauer spectra of these ribbons consist of a superimposed singlet and a broadened magnetic sextet. The singlet with isomer shift δ = -0.11 mm/s can be assigned to γ-Fe austenite phase. Minor bulk magnetic changes in the alloy were measured as a consequence of these treatments, as analyzed from the resulting transmission Mossbauer spectra. X-ray diffraction and Mossbauer data of the crystallized samples are also reported. A qualitative assessment on the mechanical properties of the alloy associated with the presence of the γ-Fe phase is given. This γ-Fe phase can also be produced by simply heating the ribbons at temperatures as low as 423 K, an unexpected result.