Formation and thermal properties of Fe-based BMG’s with Y or Gd addition

In the present work, the glass formation of Fe50-xCr15Mo14C15B6Mx (x = 0,2 and M = Y,Gd) alloys has been investigated. Wedge shaped bulk samples, with thickness from 2 mm up to 5 mm, were prepared by copper mold casting technique. Ribbons of the same compositions, with 30 ìm in thickness, were produced by melt-spinning technique. Thermal and structural properties were measured using High Temperature Differential Scanning Calorimetry and X-ray diffraction, respectively. The microstructure has been observed by Scanning Electron Microscopy and chemical composition was checked by Energy Dispersion Spectroscopy. In the case of ribbons, fully amorphous phase was observed for all compositions. Copper mold casting technique leads to a fully amorphous structure for bulk samples up to 2 mm only for composition containing Y or Gd. Such elements can act as oxygen scavengers, avoiding heterogeneous nucleation. The role of Y and Gd on glass formation is also discussed on the basis of the melting behavior.