Glass formability and fragility of Fe61Co9−xZr8Mo5WxB17 (x = 0 and 2) bulk metallic glassy alloys

The glass-forming ability (GFA) of Fe61Co9−xZr8Mo5WxB17 (x = 0 and 2) alloys was investigated in terms of the temperature interval of the melting process ΔTm, the reduced glass transition temperature Trg, the modified GFA parameter γm, as well as the packing density ρmeas/ρcal. The GFA parameters indicate that tungsten increases the glass formability of the alloys. The fragility of the alloys was discussed according to the Vogel–Fulcher–Tamman (VFT) equation, showing the fragility indexes of 47 and 39 for tungsten contents of 0 and 2 at.%, respectively. The role of the tungsten in the alloys has been discussed from the minor addition technological point of view.