Abstract
NANOPERM-type alloy with chemical composition Fe76Mo8CuB15 was studied by combination of 57Fe Mössbauer spectroscopy and 57Fe(10B,11B) nuclear magnetic resonance in order to determine distribution of hyperfine magnetic fields and evolution of relative concentration of Fe-containing crystalline phases within the surface layer and the volume of the nanocrystallized ribbons with annealing temperature. Differential scanning calorimetry revealed two crystallization stages at Tx1 ~ 510 oC and Tx2 ~ 640 oC, connected to precipitation of α-Fe and Fe(Mo,B) nanocrystals, respectively.
The amorphous and partially crystalline state was obtained by annealing at several temperatures in the range 510-650 oC. The combination of conversion electron (CEMS) and transmission Mossbauer spectrometry (TMS) showed that annealing induces crystallization starting from both surfaces of the ribbons.
For the as-quenched sample, scanning electron microscopy (SEM) and CEMS revealed significant differences in the "air" and "wheel" sides of the ribbons, crystallites were preferentially formed at the latter. While SEM micrographs of annealed samples showed various mean diameters of the crystals at opposite sides of the ribbons, the amounts of crystalline volume derived from the CEMS spectra approximately equaled.Mössbauer spectra of annealed samples contained narrow sextet ascribed to crystalline α-Fe phase, three sextets with distribution of hyperfine field assigned to the interface regions.