Understanding the Mechanisms of the Pulsed Electric Current Process for Joining Oxide-Dispersion-Strengthened Alloys

用于基础设施和运输的下一代组件，如发电厂和航空发动机，必须在越来越高的温度环境中运行，以实现最大的性能和输出效率。为了实现高温操作，将需要在各种极端环境中具有高强度的新材料。一种被称为氧化物弥散强化（ODS）合金的有前途的新型材料具有在这些环境中发挥作用的潜力。然而，这些合金的工业应用受到现有连接技术的限制，因为传统的连接工艺在ODS合金中引起微米级的反应，导致接头机械强度的劣化。脉冲电流连接工艺已成为一种有前途的方法，可以产生一个优秀的ODS合金接头，在微米尺度上的变化最小。该奖项支持基础研究，以了解脉冲电流连接过程，ODS合金微观结构和接头性能之间的关系，深入了解实现高性能接头的机制。这些新知识将使这些高性能材料能够应用于交通、能源和基础设施。该研究将被整合到一系列针对本科生的教育活动中，同时也是面向未被充分代表的中学生群体的推广活动的一部分，以激发材料工程的兴趣。本项目的目标是了解氧化物弥散强化合金脉冲电流（PEC）连接过程中活跃的基本工艺-微观结构-性能关系。假设PEC连接过程是由电流激活机制驱动的，包括通过电迁移和表面氧化膜的介电击穿增强的质量传输。为了完成研究目标并验证假设，本项目将追求三个研究目标：1）对脉冲电流连接过程中的机制进行原位透射电子显微镜研究; 2）对脉冲电流连接过程中的机制进行非原位研究; 3）使用脉冲电流连接机制进一步改善ODS合金接头。从这项工作中获得的新知识可以转化为使用脉冲电流工艺连接其他材料的策略，这些材料在连接过程中需要最小的微观结构变化，包括极端环境下的高强度材料。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Next-generation components for infrastructure and transportation, such as power plants and aeronautical engines, must operate in increasingly high temperature environments for maximum performance and output efficiency. To enable high-temperature operations, new materials will be required with high strengths in a variety of extreme environments. A promising class of novel materials known as Oxide Dispersion Strengthened (ODS) Alloys have the potential to perform in these environments. The industrial applications of these alloys, however, have been limited by existing joining technology, because traditional joining processes cause reactions at the micrometer scale in ODS alloys that lead to the deterioration of the joint's mechanical strength. The pulsed electric current joining process has emerged as a promising approach that can produce an outstanding ODS alloy joint with minimal changes at the micrometer scale. This award supports fundamental research to understand the relationships among the pulsed electric current joining process, the ODS alloy microstructure, and the resulting properties of the joints, giving insight into the mechanisms that enable high performance joints. This new knowledge will enable the translation of these high performance materials to applications in transportation, energy, and infrastructure. The research will be integrated into a series of educational activities for undergraduate students, as well as part of outreach to middle school students from underrepresented groups to inspire excitement in Materials Engineering.The goal of this project is to understand the fundamental processing-microstructure-property relationships active during pulsed electric current (PEC) joining of Oxide Dispersion Strengthened alloys. The hypothesis is that the PEC joining process is driven by electrical current activation mechanisms, including enhanced mass transport by electromigration and dielectric breakdown of the surface oxide film. To complete the research goal and test the hypothesis, this project will pursue three research objectives: 1) perform in-situ transmission electron microscopy investigation of the mechanisms in the pulse electric current joining process; 2) conduct ex-situ investigation of the mechanisms in this process; and 3) further improve ODS alloy joints using pulsed electric current joining mechanisms. The new knowledge gained from this work can be translated into strategies for using the pulsed electric current process to join other materials requiring minimal microstructural changes during the joining process, including high strength materials for extreme environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.