Correlation between fragility and structural relaxation dynamics of bulk metallic glass-forming liquids

A new approach to judge bulk metallic glass (BMG)-forming liquids to be fragile or strong was proposed according to the viscosity scatter near glass transition temperature Tg observed in creep test. The more fragile the BMG is, the weaker viscosity scatter could be on the measured viscosity curve. This phenomenon can be interpreted in terms of the α-relaxation dynamics of the supercooled liquids. Rapid recovery of α-relaxation implies a fragile character. It was also found that strong BMG can behave similar to a fragile BMG at high heating rates.

► A damped data scatter of viscosity of metallic glass in creep test is found.
► The fragility of metallic glass is found to correlate with data scatter.
► The data scatter damps faster with increasing heat rate.
► A strong liquid can behave similar to a fragile one at high heating rates.
► The fragility is dominated by the structural relaxation dynamics.