Free volume and viscosity of Fe–Co–Cr–Mo–C–B–Y bulk metallic glasses and their correlation with glass-forming ability

In this work, the variation of the glass-forming ability (GFA) in Fe–Co–Cr–Mo–C–B–Y alloy system with Co addition has been investigated from the viewpoints of non-isothermal viscosity and free volume. The best GFA for the alloy containing 7% Co is found to closely relate with its highest viscosity, and the minimum sizes and lowest concentrations of the intermediate and largest open volumes. The results may provide more insights into the formation mechanism of metallic glasses.

► The GFA of Fe-based BMGs was investigated from the viewpoints of viscosity and free volume.
► The best GFA is found to closely relate to the highest viscosity.
► The intermediate and largest free volumes play a crucial role in atomic diffusion processes.
► The Co7 alloy is supposed to possess the worst atomic diffusion ability and thus the best GFA.