The thermophysical properties, including the specific volume V, the surface tension , and the viscosity , of a Cu 46 Zr 42 Al 7 Y 5 bulk metallic glass in the molten state were investigated using a containerless high-temperature high-vacuum electrostatic levitation technique. Bulk-metallic glasses ͑BMGs͒ often show an extraordinarily high strength and low room-temperature ductility. [1][2][3] Recent studies indicated that the room-temperature ductility of BMG alloys is intrinsically related to their low Poisson's ratio. [4][5][6] Pd-, Pt-, and Au-based BMG alloys show a good ductility compared with other BMG alloys due to a high Poisson's ratio of these alloys ͑Ϸ0.4͒.4,7 Nivikov and Sokolov 8 reported that Poisson's ratio of glasses at room temperature is closely related to the fragility of glassforming liquids, which measures the steepness of viscosity changes with the temperature. Compared with a strong liquid, a fragile liquid shows a steeper change in the viscosity around the glass-transition temperature T g , and a smoother change in the viscosity around the melting temperature T m .
9Taken together, the viscosity change at high temperatures may be associated with the room-temperature mechanical properties. A fragile liquid with a high value of Poisson's ratio is expected to exhibit good room-temperature ductility. Moreover, according to the classical nucleation theory, 10 the viscosity at high temperatures, along with other thermophysical properties, will influence the glass-forming ability ͑GFA͒ of liquids. Therefore, the thermophysical properties ͑i.e., the specific volume V, the surface tension , and the viscosity, ͒ of the glass-forming liquids are important parameters, which help understand both the room-temperature mechanical properties and the GFA.In this letter, we reported the measurements of the thermophysical properties of a Cu 46 Zr 42 Al 7 Y 5 bulk metallic glass-forming liquid using a containerless high-temperature high-vacuum electrostatic levitation ͑ESL͒ technique. The Cu 46 Zr 42 Al 7 Y 5 BMG alloy shows a good GFA with a maximum thickness of 10 mm when fabricated using the coppermold casting.
11The master Cu 46 Zr 42 Al 7 Y 5 alloy was prepared by melting a mixture of the high-purity Cu ͑99.999%͒, Zr ͑99.9%͒, Ti ͑99.99%͒, Al ͑99.999%͒, and Y ͑99.99%͒ in a mini arcmelter under a Ti-gettered argon gas atmosphere. To ensure the homogeneity, the samples were melted for at least five times. Calorimetric measurements indicate T g = 675 K and T m = 1123 K for the as-cast Cu 46 Zr 42 Al 7 Y 5 BMG alloy. A sample of about 20 mg was levitated between a pair of electrodes in the ESL, which was evacuated to 10 −8 torr. The BMG sample was heated by a high-power cw Nd: YAG ͑yt-trium aluminum garnet͒ laser, and was cooled by turning off the laser power completely. The temperature of the sample was determined using a two-color pyrometer. The specific volumes of the liquid and crystal were measured by monitoring the sample volume evolution using a change-coupled device ͑CCD͒ camera with a telescopic head...