Pb-Cu-Ag Alloy And Vacuum Distillation Molecular Dynamics Simulation Study

The properties of structure, thermodynamic and diffusion for liquid metal have an important impact on the performance of the materials, separation and purification of the alloy. The properties of liquid metal have been researched for a long time and obtained many experiment data under certain conditions. However, it is difficult to measure these properties through the experimental method one by one due to the huge amount of liquid metal. Molecular dynamics method has been widely applied in the research of condensed state phenomena, such as liquid structure, surface and interface performance, relaxation processes. Using molecular dynamics method to obtain these properties have huge advantage compared with traditional experimental methods, such as easy to operate without cost expensive experimental material, be able to simulate the property of the substances under special conditions that can not be obtained by experiment method, and intuitive access to the material chemical changes. In this paper, molecular dynamics simulations has been used to acquire the properties of structure, thermodynamic and diffusion under different temperature for lead-copper and lead-sliver alloy. These alloys are familiar in the field of metallurgy. Thermodynamics calculation and experiment research by vacuum distillation have been implement. Experiment research investigated the influence of distillation temperature, distillation time and the thickness of material layer to separation and enrichment effect.Using molecular dynamic method to simulate the properties of diffusion and structure for lead-copper and lead-sliver alloy. The potential function was GEAM, time step set to5fs and number of steps to105steps, the system is set to NVT ensemble. The radial distribution function and mean-square displacement have been acquired. The calculation of the radial distribution function shows that there is a strong interaction between Pb-Pb and Cu-Cu atoms, the weak interaction between the Pb-Cu atoms. The interaction of Cu-Cu atoms is the strongest in lead-cooper alloy. With the rise of temperature, the interaction between the same kind of atom have no significant change, but the interaction between the dissimilar atoms continuously weakened. There is a strong interaction between the three kinds of atoms in lead-sliver alloy. With the temperature increase, the interaction between the Pb-Pb and Ag-Ag atoms are continuously decreased and Pb-Ag atoms are constantly strengthen. The activities coefficient of lead-copper and lead-sliver alloy were calculated by MIVM model. Compare the activities coefficient with experiment data and found certain error are exist.The simulation of diffusion coefficient for lead-copper and lead-sliver alloy show that the diffusion coefficient of two alloys increases with the temperature increasing。Diffusion coefficient values of lead-copper alloy vary from0.104×10-8m2s-1to0.247×10-8m2s-1within temperature range from1073to1473K. The values of lead-sliver alloy is0.278～0.494×10-8m2s-1. Those values correspond with the general rules of the alloy diffusion coefficient values and demonstrate the feasibility of using molecule dynamic simulation to acquire diffusion coefficient of alloy.The theoretical calculation show that these three kind of alloy can be effective separation and enrichment by vacuum distillation and getting high purity metal. Experiment research on these three alloy by vacuum distillation have been carry on and acquired the optimum conditions.The optimum conditions for these three alloy are listed below:for lead-copper alloy,distillation temperature1373K, distillation time30min, materials thickness6mm; for lead-sliver alloy, distillation temperature1273K, distillation time45min, materials thickness6～8mm; for lead-copper-sliver alloy, distillation temperature1273K, distillation time60min; for copper-sliver alloy, distillation temperature1573K, distillation time50min.