Investigation of Viscosity Measurements of Molten Fe-Si-B-Nb Alloys

The properties of Iron-based metallic glasses, such as glass-forming ability and soft magnetic properties, (MGs) have been widely investigated. However, seldom reports are available concerning the properties of these iron-based melts. In the present work, the viscosity of superheated Fe-Si-B-Nb metallic glass forming liquids (MGFLs) was measured by a torsional oscillating viscometer. It has been found that the crucial condition to get viscosity data using graphite crucibles is to reach a superheated degree of at least 250 K for melts prior to measurements. The viscosity increases monotonically with a decrease in temperature before solidification, without distinct changes of dynamic mechanism during cooling. The present work indicates that these iron-based melts are heterogeneous even above the liquidus temperature. This finding helps to understand the melts of iron-based MGs and to improve the production process of iron-based glass ribbons.

Investigation of Viscosity Measurements of Molten Cu-Zr-Al Alloys

Viscosity reflects kinetic behaviors of metallic glass liquids, as well as the changes of structures of liquids with temperature. In the present work, the viscosity of superheated Cu-Zr-Al alloys has been detected by a torsional oscillating viscometer, and the experimental parameters have been explored. The experimental results indicate that Cu-Zr-Al alloys react with corundum crucibles and are not oxidated easily in the viscometer. In addition, the influence of thermal history on viscosity measurements is not inconsiderable. By eliminating the above factors, an abnormal three-stage trend of viscosity changes is observed finally. Analysis shows that this abnormal dynamic phenomenon probably is attributed to the transition of clusters in different temperature ranges of the glass liquids, and might correspond to the abnormal thermodynamic behavior observed in Cu-Zr-Al liquids.

Theory of the Oscillating Viscometer for Slip Flow

The theory of the oscillating viscometer has been extended for a slip boundary condition. The cases considered here are: an infinite disk, an infinite cylinder, a sphere, and a pile of infinite disks. This study has prepared the way for the formulation of a new method for measuring the amount of slip experienced by bodies moving in gases outside the continuum regime. The theory of Kestin and Wang [11] has been extended to include slip at the boundary.