The Viscosity Of Ag-Sn Alloys And The Liquid/Solid Diffusion Of Al/Ag Under The Magnetic Field

When the gradient of a property such as temperature exists in a liquid, a transport process occurs in that liquid. The well-known transport processes of momentum, mass, and energy involve viscosity and diffusion. As the sensitive physical property of metal melts, the viscosity and diffusion of metal melts can build the connection between atomic structure and metal alloy properties. Viscosity and diffusion are measures of the friction among atoms. Therefore, the research of the viscosity and diffusion of metal melts is of great significance for fundamental science and technological application.The viscosity and diffusion of metal melts provides an approach to understand the action of metal melts. There is a liner relationship between the viscosity and the reciprocal of diffusion coefficient. The investigation in this article about the effect of the magnetic field on the viscosity and diffusion would provide some data and theory basis for further study. First, the dynamic viscosity of Ag-Sn alloys with different compositions were systematically studied using high-temperature viscometer with and without a horizontal magnetic field. The research mainly focused on the influence of composition and temperature and magnetic field on the viscosity of metal melts. Meanwhile, the influence of the magnetic field on the diffusion of Al/Ag couples were studied, and the influence on the microstructure of the diffusion layers was also discussed.The experimental results showed that the viscosities of Ag-Sn melts increase with decreasing temperature and fit well with Arrhenius equation. The viscosity of pure silver is higher than the viscosity of pure tin at the same superheat temperature. The viscosities of pure silver, pure tin and Ag-Sn melts increase with decreasing temperature and fit well with Arrhenius formula, whether the magnetic field is applied or not. A conclusion can be got from the experiments that the effects of magnetic field on the viscosity of pure silver generally were lager than those of pure tin and Ag-Sn melts. And the effect of magnetic field on the viscosity of Agso.4Sn49.6 was minimal. Meanwhile, the pre-exponential factor of Arrhenius equation increases under the magnetic field. And with the additional magnetic field, drastic changes appeared in the activation energy and pre-exponential of Arrhenius formula.The effects of a 0.2T magnetic field on the solid/liquid diffusion behavior in Al/Ag alloys under thermal treatment have been investigated by using the diffusion couple method. The interdiffusion rate in the Al/Ag couple was retarded by the magnetic field. The influence of a static magnetic field on the interdiffusion rate in the Al/Ag couple has a close relationship to the susceptibility of the solute and the solvent. When Al is put on top during the heating treatment, the diffusion zone was composed of five layers of stable compounds Al, AgAl4,δ, β and Ag regardless of the existence and the absence of the magnetic field. When Ag is put on top during the annealing treatment, a complete diffusion in Al/Ag alloys is observed with the formation of mainly a δ phase. The grain size is reduced significantly in the sample thermally treated under the magnetic field which is believed to be caused by the Lorentz force. The growth direction and the spatial distribution of the crystals have an obvious trend in the sample treated under the magnetic field.