电磁场诱发混沌对流对半固态A356-RE合金凝固组织的影响

Solidification process and control of alloy are the important basic technique to realize the high performance precision forming manufacturing, in which there are the great effects of melt flow during the solidification on the microstructure of alloy. The core of the scientific connotation on control of melt flow during the solidification is still how to optimize the microstructure of the alloy. The research on the theory and controlling technique of melt flow of the alloy has the important scientific significance for realizing the integrated forming manufacturing of shape and performance for aluminum alloy. Based on the non-equilibrium solidification in semisolid A356-RE alloy melt in this project, and taking the research on benefit and effect of chaotic advection induced by the electromagnetic field in A356-RE alloy melt on microstructure in the alloy as the major clue, as well as taking the effects of the diffusion of RE element in the alloy melt on the microstructure of the Al alloy as the bridge, some investigations will be carried out for the use of metal solidification theory, hydrodynamic, nonlinear scientific theory and so on. The mechanism of chaotic advection induced by electromagnetic field in the melt and the affecting factors are researched, and the diffusive characteristic and distributing law of RE element under the action of the chaotic advection are cognized. The refining effects of the chaotic advection on microstructure in semisolid Al alloy are revealed through dissecting the distribution of RE element. The regulation and control of the chaotic advection in the alloy melt is realized to hard endow the microstructure of semisolid A356-RE alloy with the suitable morphology and size. The basis is established for developing the complex forming technology of semisolid alloy with high efficiency and saving energy and enriching the solidification theory of metal.

合金的凝固成形与控制是实现高性能精确成形制造的重要基础环节，合金凝固时熔体流动对其组织影响极大，调控合金凝固时熔体流动的科学内涵核心仍是如何优化合金凝固组织的问题。合金熔体流动理论与控制技术的研究对于实现铝合金成形成性一体化制造具有重要科学意义。本项目以半固态A356-RE合金非平衡凝固过程为基础；以电磁场诱发A356-RE合金熔混沌对流对合金凝固组织的影响和效应研究为主线；以稀土在铝合金熔体中扩散过程及其对铝合金凝固组织的影响为桥梁；应用金属凝固理论、流体动力学、非线性科学理论等，研究电磁场诱发混沌对流的机制及影响因素，认知混沌对流作用下稀土在熔体中扩散特征和分布规律；通过剖析稀土分布规律揭示混沌对流对半固态铝合金凝固组织的影响，实现调控合金熔体中的混沌对流，力争赋予半固态A356-RE合金具有合适的凝固组织形貌与尺寸，为创建高效节能的半固态合金复合成形技术和丰富金属凝固理论奠定基础。

合金熔体流动理论与控制技术的研究对于实现铝合金成形成性一体化制造具有重要科学意义。本项目以半固态A356-RE合金非平衡凝固过程为基础；以电磁场诱发A356-RE合金熔混沌对流对合金凝固组织的影响和效应研究为主线；以稀土在铝合金熔体中扩散过程及其对铝合金凝固组织的影响为桥梁；应用金属凝固理论、流体动力学、非线性科学理论等，研究电磁场诱发混沌对流的机制及影响因素，认知混沌对流作用下稀土在熔体中扩散特征和分布规律；通过剖析稀土分布规律揭示混沌对流对半固态铝合金凝固组织的影响，实现调控合金熔体中的混沌对流，力争赋予半固态A356-RE合金具有合适的凝固组织形貌与尺寸。 通过实验和理论研究，开发了多元稀土双重梯度保温的制备半固态铝合金浆料新技术，研究了稀土Nd与铝合金熔体的相互作用以及诱发的共晶反应产物细化半固态铝合金凝固组织的作用。开展了电磁搅拌下半固态A356铝合金凝固时熔体流动与组织的研究；进行了电磁搅拌下半固态A356铝合金凝固时电磁场-流场数值模拟与实验研究，探究了电磁搅拌参数对非圆坩埚中半固态铝合金熔体流动与凝固组织的影响。应用数值模拟技术研究了若干制备工艺中电磁场特性及其对半固态铝合金熔体流动性能与凝固组织的影响，包括分级电磁搅拌中电磁场的特性及其对半固态铝合金熔体流动及凝固组织的影响、电磁搅拌下电流突变对磁场及半固态铝合金凝固组织的影响。开展了电磁场作用下半固态Al-RE合金熔体流动特性及其对凝固组织与稀土分布的影响，包括半固态A356-0.4%Gd合金制备过程的电磁场模拟与试验研究和双向电磁搅拌对半固态铝合金中稀土分布的影响。最后，总结了近些年来国内外在电磁场作用下半固态合金熔体流动行为以及诱发混沌对流对凝固组织影响的研究工作，包括电磁场作用下半固态合金熔体流动行为对凝固组织影响、电磁场诱发的半固态合金熔体混沌对流及其对凝固组织影响。本项目的工作结果及后续的研究可为创建高效节能的半固态合金复合成形技术和丰富金属凝固理论提供积极的支持。