CAREER: Assessing Low Temperature Phase Stability through Irradiation

非技术性描述：在中等高温（200 - 500 ° C）下长期使用的合金属于技术空白，温度影响非常缓慢，但随着时间的推移变得显著。该温度范围在许多重要的技术行业中至关重要，例如航空航天、能源生产和石化工厂。在几十年的时间里，这些材料会降解，不再按设计发挥作用，可能会引起安全问题。在这些温度下对合金降解的实验室研究仍然需要许多年才能完成，而且往往是不切实际的。该项目建议使用辐照作为一种工具，通过在晶格中产生更多的缺陷来加速低温扩散。这种方法有望加速相变，使性能降低几个数量级，这将使实验室研究可行。将进行长期的热老化实验，以基准的辐射结果和原子扩散的计算模拟将进行，以帮助解释这两种方法之间的差异。辐照增强方法的成功演示将使我们能够识别新的、稳定的低温相的演变，并预测在役合金的使用寿命。此外，我们希望能够利用这些知识来设计更适合抵抗长期热降解的新合金。该项目还旨在作为一种工具，从代表性不足的群体中招募和留住未来一代的工程师和科学家。通过整合两个导师项目，将俄勒冈州的高中生、本科生和研究生以及教授聚集在一起，实验室中的导师金字塔正在形成。技术说明：在200 - 500 ° C温度范围内长期使用的合金，属于技术空白，其中原子扩散非常缓慢，但变得显著，由于缓慢扩散，相图通常不完整。该温度范围在许多重要的技术行业中至关重要，例如航空航天、能源生产和石化工厂。通过将辐照作为材料研究的积极工具，我们期望能够通过辐照增强相变准确地获得这些低温数据。这种方法的有效性的成功演示将允许识别新的，稳定的低温相，并在一个实际的时间范围内验证动力学转化模型。一个并行的计算研究将被用来解释热和辐射辅助相变之间的差异，并提供基本的洞察机制，控制在Ni-Cr-Fe系统的转变。反过来，设计更适合于满足未来技术需求的新合金有望成为可能。该项目的研究部分通过为Ni-Cr-Fe系统生成改进的热力学数据库并在商业软件包中实现它来推进科学界的工作。该项目支持通过武装他们与国家的最先进的实验方法和研究相变的理论方法来培训未来的材料劳动力的更广泛的目标。此外，该项目将通过两个不同的外展计划，为代表性不足的高中和本科学生群体提供研究机会，从而有助于增加STEM领域的多样性。这些研究机会和新开发的教学课程将鼓励学生探索材料科学，特别是冶金学的机会。

NON-TECHNICAL DESCRIPTION:Alloys in long-term service at moderately elevated temperatures (200-500°C), fall into a technological gap, where temperature effects are very slow but become significant over time. This temperature range is essential in many important technological industries such as aerospace, energy production and petrochemical plants. Over the period of decades, these materials can degrade and no longer perform as designed, potentially causing safety concerns. Laboratory studies of alloy degradation at these temperatures still take many years to perform and is often impractical. This project proposes to use irradiation as a tool to accelerate low temperature diffusion by creating more defects in the lattice. This method is expected to speed up the phase transformations that degrade properties by several orders of magnitude, which would make laboratory studies feasible. A long term thermal aging experiment will be performed to benchmark the irradiation results and computational simulations of atomic diffusion will be performed to help explain the differences between the two methods. Successful demonstration of the irradiation-enhanced method will allows us to identify the evolution of new, stable low-temperature phases, and to predict the service lifetime of alloys in service. Additionally, we expect to be able to use this knowledge to design new alloys that are better suited to resist long-term thermal degradation. This project is also designed to act as a vehicle for both recruiting and retaining a future generation of engineers and scientists from under-represented groups. By integration with two mentoring programs that bring Oregon high school, undergraduate and graduate students, and the professor together, a pyramid of mentorship in the laboratory is being created. TECHNICAL DESCRIPTION:Alloys in long-term service at temperatures in the range of 200-500°C, fall into a technological gap, where atomistic diffusion is very slow but becomes significant and phase diagrams are, as a consequence of the slow diffusion, usually incomplete. This temperature range is essential in many important technological industries such as aerospace, energy production and petrochemical plants. By using irradiation as a positive tool for materials research we expect to be able to accurately acquire these low-temperature data through irradiation-enhanced phase transformations. Successful demonstration of the validity of this method will allow the identification of new, stable low-temperature phases, and to validate kinetic transformation models within a practical timeframe. A parallel computational study will be used to explain differences between thermal and irradiation-assisted phase transformation and give fundamental insight into the mechanisms that control the transformation in the Ni-Cr-Fe system. In turn, the design of new alloys better suited to meet forthcoming technological needs can be expected to become possible. The research components of this project advance work of the scientific community by generating an improved thermodynamic database for the Ni-Cr-Fe system and implementing it within a commercial software package. This project supports the broader goal of training the future materials workforce by arming them with state-of-the-art experimental methods and theoretical approaches for studying phase transformations. Additionally, this project will help to increase diversity in STEM fields through research opportunities for under-represented high school and undergraduate student groups through two different outreach programs. These research opportunities and a newly-developed didactic class will encourage students to explore opportunities in materials science, specifically metallurgy.