Abstract: Viscous flow behavior of Mg₆₀Cu₃₀Y₁₀ bulk metallic glass in supercooled liquid region was investigated. The supercooled liquids exhibit that Newtonian viscosity in equilibrium state transforms to a non-Newtonian viscosity in non-equilibrium state with temperature and strain rate increasing. According to VFT (Vogel-Fulcher-Tammann) equation with the Arrhenius function, the relation between flow stress and viscosity and temperature was established. Viscous flow of Mg₆₀Cu₃₀Y₁₀ bulk metallic glass depends on temperature and strain rate. It can be described with the free-volume model and used to interpret the implement of Mg-based bulk metallic glass viscous forming process. When the temperature is higher than glass transition temperature, the number of atoms which can jump during deformation of bulk metallic glass increases. Atomic jumps are biased in the direction of the external force. This forms the plastic flow showed in macroscopic. With strain rate increasing, free volume obtained from thermal fluctuations can't meet the need of more and more atomic jumps. It results in steady state Newtonian viscosity transfer to non-Newtonian viscosity.

Key words: Mg-based bulk metallic glass; supercooled liquid region; viscous flow behavior; constitutive equation