By employing a containerless high-temperature high-vacuum electrostatic levitation technique, the thermophysical properties, including the ratio between the specific heat capacity and the hemispherical total emissivity, the specific volume, and the viscosity, of Cu 50 Zr 50 and ͑Cu 50 Zr 50 ͒ 95 Al 5 bulk-metallic-glass ͑BMG͒-forming liquids have been measured. Compared with Cu 50 Zr 50 , the improved glass-forming ability of ͑Cu 50 Zr 50 ͒ 95 Al 5 can be attributed to its dense liquid structure and its high value of viscosity. Additionally, the relationship between the viscosity of various BMG forming liquids at the melting temperature and the elastic properties of the corresponding glasses at room temperature will be compared. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2408634͔The processing, the thermophysical, and mechanical properties of low-cost Cu-based bulk-metallic glasses ͑BMGs͒ have been intensively studied recently. [1][2][3][4][5] The Cubased BMGs exhibit extraordinarily high strength and good compressive ductility, which are comparable with the Zrbased BMGs. In order to frustrate the crystal formation during the copper-mold casting process, previous studies indicate that BMG alloys should typically consist of at least three components, which have varying atomic sizes. 6 However, it was reported recently that binary Cu-Zr alloys can be cast into bulk amorphous structures with sample diameters up to 2 mm. 7-10 Subsequent studies reveal that small amounts of Al additions ͑several at. %͒ further increase its glass-forming ability ͑GFA͒ in the ternary Cu-Zr-Al alloys. 11 Das et al. 12 reported that both Cu 50 Zr 50 and ͑Cu 50 Zr 50 ͒ 95 Al 5 BMGs exhibit good compressive ductility at room temperature. Most strikingly, the Cu 50 Zr 50 and ͑Cu 50 Zr 50 ͒ 95 Al 5 BMGs exhibit "strain hardening" effects during the compressive tests, which were not expected for the BMG alloys since there is no dislocation activities in the amorphous structure. Strain hardening is a desirable factor for the prevention of the strain localization. Nevertheless, the localized deformation within the shear bands was still primarily responsible for the observed plasticity in both Cu 50 Zr 50 and ͑Cu 50 Zr 50 ͒ 95 Al 5 BMGs. 12 Therefore, the precise mechanisms responsible for the plastic deformation of the Cu 50 Zr 50 and ͑Cu 50 Zr 50 ͒ 95 Al 5 BMGs require further investigations. 13,14 Recently, it was reported that the ductility of BMGs was closely related to their Poisson's ratio. [15][16][17] For example, Ptbased BMG with high Poisson's ratio of about 0.41 shows an excellent compressive ductility. 15 Nivikov and Sokolov 18 reported that Poisson's ratio of a glass at room temperature correlates with the fragility of liquids at high temperature. This correlation was recently challenged by Yannopoulos and Johari 19 by compiling extensive experimental data covering various glass-forming systems. In this letter, in an effort to further understand the relationship between the fragility and the elastic properties of glass-...

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...