The Experiment And Theoretics Study Of Viscosity Of Cu-Sn Alloys

Viscosity is a measure of the friction among atoms. The viscosity of molten metals and alloys is a structural sensitive property. A liquid's viscosity is of great interest to both the technology and theory of liquid metal behavior. The viscosity of liquid metals and alloys plays an important role in many phenomena relevant to both fundamental science and technological application.Cu-Sn alloys are applied extensively in electric, machine, material and industry fields etc. because of their excellent electrical, mechanical, physical and chemical properties. In the present work, the dynamic viscosities for melts of Cu-Sn alloys with different compositions were systematically studied using an oscillating-cup viscometer. Moreover, the dynamic viscosities of pure copper and Cu-10wt.%Sn were measured using an oscillating-cup viscometer with a horizontal magnetic field. On the basis of these the relationships between the viscosity and liquid structure were probed attentively. The effects of the external magnetic fields on the viscosity were analyzed too. In addition, a new model, based on the statistical dynamics model, to predict the viscosities of multicomponent melts has been established.The experimental results showed that the viscosities of Cu-Sn melts increase with decreasing temperature and fit well with Arrhenius equation. The viscosity of pure Cu is higher than the viscosity of pure Sn at the same superheat temperature. Moreover, compared with the phase diagram at the same superheat temperature, the viscosity curves heave around Cu₅Sn and the viscosity is higher around the phase of β (Cu₅Sn), and the highest at Cu-25wt.%Sn. When the tin concentration is in the range of 20wt.%-40wt.%, the average rate of increasing viscosity with the decreasing temperature is higher, and the maximum appears at Cu-25wt.%Sn. The viscosities of pure copper and Cu-10wt.%Sn increase with decreasing temperature and fit well with Arrhenius formula, whether the magnetic field is applied or not. According to the magnetic field strength, significant increases of the viscosity were observed. Furthermore we found that, by the additional tin to copper melts, drastic changes appeared in the activation energy and pre-exponential factor of the Arrhenius formula. A conclusion can be got from the experiments that the effects of magnetic field on the viscosity of pure copper generally were larger than those of Cu-10wt.%Sn.A new model, based on S. Morioka's viscosity model and Chou's geometric-thermodynamic model, has been established to predict the viscosity of binary and ternary melts. The present model will enable us to calculate viscosity of a ternary or multicomponent system from the fundamental physical properties of constituent elements. The viscosities of Cu-Sn system and Au-Ag-Cu system have been calculated with the present model, and the results are consistent with the experimental data.