| Microwave sintering is a critical technology for preparation of high quality material and traditional materials which has new material's performance.It has the advantages of fast,efficient and can also improve the microstructure and macroscopic properties of materials,Microwave sintering is a complex process of multi-physical field coupling,it is of great significance to study the interaction mechanism between microwave and materials,which can demonstrate the theory of microwave sintering and guide the actual production.In this paper,microstructure evolution of powder ceramics and metals under the coupling of microwave electromagnetic field and temperature field is been simulated by phase field method,and the theory has been testified by real time experiment.The main content of this paper is as follows:1.The traditional phase field model of solid phase sintering is improved,and the effect of microwave non-thermal effect on material was introduced to simulate pore's microstructure evolution of ceramic powder.Then the theory has been testified by real time experiment.The paper explored kinetics mechanism of microwave sintering which draw on the ion conductance diffusion,based on traditional sintering mechanism of ceramic materials.The electromagnetic-thermal coupling is introduced into the phase field dynamics equation,and the phase field model of microstructure evolution is been build.And the evolution of the pore's evolution during the sintering process of ionic crystal ceramic powder under microwave electric field is simulated,the results show that under the action of microwave electric field,matter is transferred from the area under the focus of the electric field to other regions,in the evolution process,the long axis tends to change in the vertical direction of the external electric field,and the pore direction is deflected.2.The electromagnetic force between metal particles is introduced on the basis of traditional phase field model,and the micro structure evolution of powder metal microwave sintering was analyzed and simulated.Based on the eddy current effect of metal powder compaction in microwave electromagnetic field,the electromagnetic force of metal surface was analyzed,and the mechanism of microwave powder sintering was explained.By introducing this force into the phase field dynamics model,the phase field model of the microstructure evolution of the metal microwave sintering is established,and the evolution process of the elongated pore is simulated.The result shows that the elongated porosity in the metal sintering body is closed along the short axis direction,and the higher the electromagnetic field intensity is,the stronger the electromagnetic force is,and the faster the pore closure rate is.3.The SR-CT on-line observation experiment of microwave sintering alumina ceramic and aluminum was carried out,and the experimental results were compared and analyzed with the simulation results,and the reliability and accuracy of the simulation were verified.The characteristics of pore distribution of samples before and after sintering in SR-CT reconstruction of alumina were analyzed.The results show that the pore has deflected after sintering,which is consistent with the analysis and simulation results.In the online experiment of metal aluminums microwave sintering,a long pore closing effect have been observed,the evolution process of pores is simulated based on experimental images.It is shown that the results of the simulation are fairly agreement with the theoretical results and experiments,thus the theory is been confirmed.In this paper,the microstructure evolution mechanism of ceramic and metal microwave sintering is studied through theoretical analysis,numerical simulation and experimental verification.By theory,simulation and experimental validation and support each other,the prediction of the actual sintering process is realized,it provides a theoretical basis and an analytical approach for exploring the microstructure evolution of materials under multiple field coupling. |
PDF Full Text Request