Medium-range order and viscosity of molten Cu-23% Sn alloy

The structures of molten Cu-23% Sn alloy at different temperatures have been determined by using a high-temperature Xray diffractometer. It has been found that there exist not only short-range order (SRO) structure but also medium-range order (MRO) structure in the molten alloy. The medium-range order structure in the alloy melt is a function of temperature. There exist obvious medium-range order structure at the range of temperatures from 900 to 1200 degreesC. The medium-range order structure disappears when the temperature reaches 1300 degreesC. The temperature dependence of the dynamic viscosity of the alloy melt has been measured using a torsional oscillation viscometer. It has been found that there is an abnormal change in the relationship between the temperature and the viscosity of the alloy melt. The abnormity change is consistent with the transformation from medium-range order to short-range order in the alloy melt. (C) 2002 Elsevier Science B.V. All rights reserved.