Abstract
The supercooled liquid range (ΔTx) was calculated on the basis of the free volume theory proposed by Beukel and Sietsma. A differential equation which expresses the change in free volume from a non-equilibrium to an equilibrium state has been analyzed numerically for Ni, metallic glasses and SiO2 systems. The Vogel-Fulcher-Tammann (VFT) equation for viscosity was used to define the equilibrium free volume. The maximum ΔTx was calculated as 56 K for the SiO2 system. The calculated ΔTx was approximately six times smaller than the experimental result. The calculation results of the logRc (Rc: critical cooling rate for glass formation)-ΔTx diagram shows a tendency similar to the experimental result; logRc decreases linearly with increasing ΔTx. An approximate solution of the differential equation was also obtained with elementary functions. It was found that the glass transition temperature (Tg) and ΔTx can be obtained schematically in the free-volume-temperature diagram. All the factors expressing the glass-forming ability of the metallic glasses can be derived from the VFT parameters.
