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

用于基础设施和交通运输的下一代部件，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，以实现最高性能和输出效率。为了能够在高温下运行，需要在各种极端环境中具有高强度的新材料。氧化物弥散强化(Ods)合金是一类很有前途的新型材料，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一直受到现有连接技术的限制，因为传统的连接工艺会在ODS合金中引起微米级的反应，导致接头机械强度的恶化。脉冲电流连接是一种很有前途的方法，它可以在微米级产生最小的变化来获得性能优异的ODS合金接头。该奖项支持基础研究，以了解脉冲电流连接过程、ods合金组织和由此产生的接头性能之间的关系，从而深入了解实现高性能接头的机制。这一新知识将使这些高性能材料能够转化为在交通、能源和基础设施中的应用。这项研究将被整合到面向本科生的一系列教育活动中，以及面向未被充分代表的群体的中学生的推广活动，以激发材料工程学的兴趣。该项目的目标是了解在脉冲电流(PEC)连接氧化物弥散强化合金时活跃的基本工艺-组织-性能关系。假设PEC的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来增强质量传输。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理进行原位透射电子显微镜研究；2)对该过程中的机理进行异地研究；3)利用脉冲电流连接机制进一步改进ods合金接头。从这项工作中获得的新知识可以转化为战略，利用脉冲电流过程加入在连接过程中需要最小微结构变化的其他材料，包括用于极端环境的高强度材料。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.