基于相场模型的金属微波烧结演化机制分析及同步辐射断层扫描实验验证

为了探索不同种类金属材料的微波烧结机制,本文针对钛和铝两种具有不同电磁学特性的金属材料,分析了微波与金属微粒的相互作用。依据经典的麦克斯韦方程,金属表面产生电子涡流和趋肤效应。由P.Mishra和K.I.Rybakov等提出的金属在微波中的加热效率理论,推导出钛金属表面的热效应明显高于铝。因为电子涡流在磁场中产生指向颗粒内部的洛伦兹力这一微波非热效应,阻碍了内部物质向外的扩散,且铝的感应涡流大于钛,故其向心力更大。由于微波的热效应和非热效应导致物质扩散的驱动力不同,得出"钛的微波烧结速率明显大于铝"这一区别于常规烧结的结论。将获得的分析结果引入相场数值模拟,改变相场模型中控制演化过程中的表面和体扩散变量,获得不同的模拟结果,定量分析了烧结颈等微观结构参数随模拟时间的演化曲线。结合同步辐射断层扫描(SR-CT)技术获得的金属在微波烧结过程中的实验参数,与理论分析和模拟结果相吻合,从而验证了分析和模拟的正确性和可行性。上述结果可为研究金属在微波烧结过程中的演化机制提供支持。

Evolution Mechanism Analysis of Metal Microwave Sintering Based on Phase-Field Model and its Experimental Validation by SR-CT

In order to explore the mechanism of microwave sintering of different kinds of metal material, in this paper, both titanium and aluminum with different electromagnetic characteristics were selected, the interaction between microwave and metal particles was analyzed. According to classical Maxwell equations, eddy current and skin effect are generated on metal surface. Based on the microwave heating efficiency theory proposed by P. Mishra and K. I. Rybakov, it is derived that thermal effect of titanium is much higher than that of aluminum. Since Lorentz force generated by eddy current and pointing to the interior of particles has non-thermal effect and hinders the outward diffusion of internal matter, and the induced eddy current of aluminum is larger than that of titanium, so its centripetal force is larger than that of titanium. The driving force of material diffusion is different due to the thermal effect and non thermal effect of microwave. It is concluded that the microwave sintering rate of titanium is obviously larger than that of aluminum, which is different from conventional sintering. Introducing analysis results into phase field numerical simulation, changing the surface and bulk diffusion variables, which control the evolution process, in phase field model, different results were obtained. Quantitative analysis of the evolution of sintering neck and microstructure parameters with the simulation time was carried out. The experimental parameters obtained by synchrotron radiation computed tomography (SR-CT) technology are consistent with the theoretical analysis and simulation results, which verify the correctness and feasibility of the analysis and simulation. Above results may provide support for the study of mechanism evolution of metal subjected to microwave sintering.