Viscosity measurements of the Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass forming alloy using parallel plate rheometry and beam-bending

Parallel plate rheometry and three-point beam-bending were used to measure the viscosity as a function of temperature of a bulk metallic glass, Zr46.75Ti8.25Cu7.5Ni10Be27.5 The high thermal stability above the glass transition of this bulk metallic glass former with respect to crystallization allows measuring viscosities 120 K into the supercooled liquid region. Viscosity in the range from 10(10) to 10(6) poise has been measured using parallel plate rheometry, a region of viscosities that has not been previously accessible for supercooled metallic melts. The measurements were carried out with different heating rates between 0.0167 K/s and 1.167 K/s as well as isothermally. Using three-point beam bending, viscosity in the range from 10(13) to 10(8) poise has also been measured. These two methods, which involve completely different geometries for the measurement of flow, yielded consistent values for viscosity where their applicable regions overlap. The viscosity of the supercooled liquid of this bulk glass former, above the glass transition temperature, exhibits a small Vogel-Fulcher temperature relative to the glass transition temperature similar to silicate glasses.