Defect-Electron Interaction at Ambient Temperature in Metallic Materials

非技术摘要自史前时代以来，高温就被用于金属材料的加工。高热将原本不能移动的内部缺陷移出，从而改善了性能。同样的原则在今天也在使用。例如，钢的加工需要超过800C的温度，并持续数小时。这一研究项目旨在通过提出这样一个问题来改变目前的最先进水平：金属可以在室温下加工吗？假设是，通过通过高电流，但不允许温度上升，可以在材料内部产生纯粹的机械力。这种力可以使缺陷在不升高温度的情况下移动，并且只需几分钟的时间。因此，本研究的目的是了解(来自电流的)电子如何与缺陷相互作用，以及缺陷的消除或重排与传统热处理有何不同。这些实验是在高倍率显微镜中进行的，以发展对所提议的过程的基本见解。该项目的完成将为金属加工业提供一个新的选择，该行业消耗了美国很大一部分能源(和碳)足迹。这项新科学也可以应用到其他可以传递电流的系统中，比如电子设备。通过绕过高温，这一新工艺可能会影响制造业的经济。直接的影响是对研究生和本科生进行教育和培训，同时促进多样性。该项目涉及从中学到下一代的学生，以提高对制造业和基础科学的碳经济的认识。技术概述金属和合金中的缺陷和微观结构控制需要非常高的温度(与熔点相当)和长时间(从几个小时到几天)。在这个项目中，PI提出了一种非热力，以在几分钟内达到同样的效果。在这里，电流通过样品，同时控制其温度到环境。当电子与缺陷和晶界碰撞时，它们就会失去动量，从而产生“电子风力”(EWF)。假设EWF解离了固定的和复杂的缺陷物种，从而产生了非常高密度的无纠缠和可移动的位错。这使得EWF可以在不提高温度的情况下将高迁移率赋予缺陷。该项目的具体目标是：(A)通过在近原子分辨率的显微镜内进行基本实验，提供缺陷和微观结构控制的直接证据，(B)研究电子-缺陷相互作用，以预测各种缺陷物种(空位、偏位、位错、孪晶)的演变，并将其与微观结构变化联系起来。该项目的变革性方面是从数百年的热处理技术转向拟议的非热工艺。它探索了缺陷-EWF相互作用的原子到颗粒水平的基本原理，这些基本原理仍然大多未知。这项研究与本科教育相结合，通过High Capstone设计课程培养具有新兴制造技术的下一代人。招生是通过宾夕法尼亚州立大学的工程少数民族/妇女计划进行的。为中学生开发了一个独特的推广项目--用金属打印。与这些活动相辅相成的是制造业日活动，旨在吸引高中生走向工程学，特别是下一代制造业。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。

Non-technical SummaryHigh temperature has been used to process metallic materials since prehistoric times. The intense heat moves out the otherwise immobile internal defects and thus improves the properties. The same principle is used today. For example, steel processing requires temperatures in excess of 800 C applied for many hours. This research project aims to transform the current state-of-the-art by asking the question, can metals be processed at room temperature? The hypothesis is that, by passing high current - but not allowing the temperature to rise, a purely mechanical force can be generated inside the material. This force can make the defects mobile without raising the temperature and in a timeframe of minutes only. Accordingly, the objective of this research is to understand how the electrons (from current flow) interact with the defects, and how the elimination or rearrangement of defects is different from conventional heat treatment. These experiments are performed inside high magnification microscopes to develop fundamental insights of the proposed process. Accomplishment of this project will give a new alternative to the metallic processing industry, which consumes a big portion of US energy (and carbon) footprint. The new science can also be employed in other systems where current can be passed, like electronics. By bypassing high temperature, this new process may impact the economy of manufacturing industry. The immediate impact is education and training of graduate and undergraduate students, while promoting diversity. The project involves student from middle school to enhance awareness of the carbon economy of manufacturing, and underlying science, to the next generation.Technical SummaryDefect and microstructural control in metals and alloys require very high temperature (comparable to melting point) and long times (from few hours to days). In this project, the PIs propose a non-thermal force to achieve the same effects in minutes. Here, electrical current is passed through the specimen, while controlling its temperature to the ambient. Whenever the electrons collide with defects and grain boundaries, they lose the momentum – generating the ‘electron wind force’ (EWF). The hypothesis is that the EWF dissociates immobile and complex defects species to create very high density of disentangled and mobile dislocations. This allows the EWF to impart high mobility to the defects without raising the temperature. The specific objectives of this project are to (a) provide direct evidence of defect and microstructural control by performing fundamental experiments inside microscopes with near-atomic resolution and (b) investigate the electron-defect interaction to predict the evolution of various defect species (vacancies, partials, dislocations, twins) and correlate that to the microstructural changes. The transformative aspect of this project is the departure from centuries-old heat treatment techniques to the proposed non-thermal process. It explores the atomic to grain level fundamentals of defect-EWF interaction, which remain mostly unknown. The research is integrated with undergraduate education through Senior Capstone design course to train the next generation with emerging manufacturing technology. A student recruitment is through the Penn State Minority/Women in Engineering program. A unique outreach program, Print with Metals, is developed for Middle school students. These activities are complemented by the Manufacturing Day event to draw high and middle school students towards engineering, and specifically next generation manufacturing careers.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.