Transmission and conversion electron Mossbauer study of crystallization ofamorphous FeZrB alloys

The combined conversion electron emission and gamma-transmission Mossbauer spectroscopy are used to investigate the differences in the bulk and surfac e crystallization of the amorphous FeZrB alloy in which the nanocrystalline bcc-Fe phase was formed due to annealing. The measurements were performed for the ribbons in the as-quenched state, after Ih annealing at 430-600 deg rees C and after short time annealing at 600 degrees C. The clear differenc es in the surface and bulk crystallization behaviours were detected. Not on ly the surface crystallization starts at lower annealing temperature than t he bulk one, but additional phases were detected at the surface which do no t form in the bulk. Structural transformations as a function of annealing t ime (15-120 s) are compared with those induced by 1 h anneals. The enhanced surface crystallization was attributed to the boron depletion of the surfa ce region which leads to the decrease in the crystallization temperature at the surface.