超声激励氧化铝钎缝原位自生陶瓷相的耐高温接头形成机理研究

High quality ceramic joining is the key for extensive applications of high performance ceramics. The most difficulties are relied on the completely interfacial wetting in air and the seam qualities similar to their ceramic matrix. Through formation of ceramic-phase during the ordering processes at the interface of the molten metallic alloys and ceramic matrix to decrease the interface energy through reaction wetting, the wettability will be increased. And with the in-situ formed high-melting-temperature phases to enhance the seam, the joint performances will be highly improved. This project proposes the thoughts of combining ultrasonic brazing and transient liquid phase (TLP) bonding. Ultrasonic field motivates the strong reaction of Al-O and induces to form the joint structures filled with in-situ reacted ceramic-phase. This project is planning to investigate to braze Al2O3/Al/Al2O3 by using an ultrasonic field. With the research thread of wetting kinetics - control ultrasonics sonochemistry and efficient energy - fabricate high-melting-temperature ceramic joints, this project is aimed (1) to investigate the physical wetting processes of the molten metallic Al drop on the alumina surface disturbed under the ultrasonic field and characterize the reaction dynamics of the interfacial reactants, (2) to investigate the metallurgical functions of the local special physical-chemical circumstances formed at the liquid/solid interfaces by ultrasonics, (3) to investigate the coupled relationship of the ultrasonic efficient energy with the physical properties and dimensions of the transmitted materials , and (4) to investigate the metallography of the in-situ formed ceramic-phase filled seam stimulated by ultrasonic effects. A rapid and direct brazing method will be proposed for high-quality ceramic joining in air. Theoretical and technical supporting will be provided for completely improving the performances of ceramic joints.

高质量陶瓷连接是高性能陶瓷广泛应用的关键，大气下界面完全润湿并形成与陶瓷性能相当的焊缝是最大难点。利用界面有序化生成陶瓷相的反应润湿机制来降低界面能进而提高润湿性，并原位形成高熔点物相来增强焊缝进而提升接头性能是研究热点。本项目提出综合超声钎焊和瞬间液相焊的思想，基于超声能场激励Al-O强烈反应原位形成陶瓷相的接头结构。拟针对Al2O3/Al/Al2O3体系，以润湿反应动力学─超声声化学效应和有效能量控制─耐高温陶瓷接头成形为主线，拟开展以下研究：（1）超声扰动下熔融铝快速反应润湿氧化铝陶瓷基体的反应动力学行为；（2）超声在液/固界面产生的局域特殊物理化学环境对冶金作用的本质；（3）超声有效能量与传递材料物性和结构尺度之间耦合关系规律；（4）超声效应激励钎缝自生形成并生长陶瓷相的金属学特征规律。研究结果将提出一种大气下快速直接高质量陶瓷钎焊原理，为全面提升陶瓷接头性能提供理论和技术支撑。

高质量陶瓷连接是高性能陶瓷广泛应用的关键，大气下界面完全润湿并形成与陶瓷性能相 当的焊缝是最大难点。利用界面有序化生成陶瓷相的反应润湿机制来降低界面能进而提高润湿性，并原位形成高熔点物相来增强焊缝进而提升接头性能是研究热点。本项目综合超声钎焊和瞬间液相焊的思想，提出一种基于原位自生反应形成陶瓷相增强的复合超声钎焊-瞬间液相焊的新原理，以润湿反应动力学-超声本质（超声效应和超声有效能量）-钎缝陶瓷化为研究思路，探索了超声扰动润湿过程中气固液三相区铺展动态行为及反应物的动力学行为；揭示了超声效应产生的局域物化环境对冶金作用的本质；建立了超声有效能量与传递材料物性和结构尺度之间关系的模型；阐明了超声效应激励原位自生陶瓷相的金属学特征规律。原位自生陶瓷相增强的接头强度高于陶瓷母材，四点弯曲试验测试下氧化铝陶瓷钎焊接接头最大弯曲强度可达约400 MPa。氧化铝陶瓷焊缝室温剪切强度高于100 MPa，400℃剪切强度高于60 MPa。焊后接头的热膨胀系数仅为6.74 ppm m/℃，接近母材的6.64 ppm m/℃，变化幅度仅为1.5%，热膨胀系数表征结果证实钎缝陶瓷化率接近100%；研究结果提出了一种大气环境下氧化铝陶瓷-金属快速直接钎焊方法，为从界面和钎缝性能上全面提升接头质量提供理论和技术支撑，推广高性能氧化铝陶瓷的实际应用、提升我国氧化铝陶瓷连接整体质量和水平。

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