Glass formation from viscous metallic liquids

Viscous flow, relaxation and thermodynamics of Zr-Ti-Cu-Ni-Be bulk metallic glass (BMG) forming alloys are presented. The data are compared with the thermodynamics and kinetics of other metallic and non-metallic liquids. BMG formers are relatively viscous liquids with melt viscosities that are about three orders of magnitude larger than in pure metals and other alloys. The strong liquid behavior of these alloys is also reflected by a small entropy of fusion and a weak temperature dependence of the thermodynamic functions upon undercooling. The high viscosity and small,driving force for crystallization are major contributing factors to the high glass forming ability and low critical cooling rate.