POWRE: A Fundamental Study of Microstructual Evolution in Titanium Alloy Friction Stir Welds

POWRE：钛合金搅拌摩擦焊微观结构演变的基础研究

• 批准号: 0074267
• 负责人: Mary Juhas
• 金额: $ 7.45万
• 依托单位: Ohio State University Research Foundation -DO NOT USE
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0074267&HistoricalAwards=false
• 关键词: POWRE; Fundamental; Study; Microstructual; Evolution

This project is aimed at greater understanding of fundamental mechanisms of high temperature deformation and microstructural evolution in titanium alloy friction stir welds. Two alloys have been selected, pure(CP) titanium and Ti-6Al-4V, a + b alloy. CP titanium, used for its corrosion resistance especially in the chemical process industry, was chosen for its good formability. Ti-6Al-4V is widely used in a variety of aerospace and marine applications in welded and unwelded conditions. In addition to "normal" welds, interrupted welds, where the tool is retracted before reaching the end of the two plates to be joined, will also be evaluated. In this way, the micro-structures of the thermomechanically-affected and heat-affected zones will be compared with material just ahead of the weld. These in turn will be compared with microstructures of the stir zone (the actual dynamically recrystallized weld) and the base material. Samples will be obtained for metallographic examination in both the transverse and longitudinal directions to reveal each distinct microstructural zone and serve as a map for the eventual location of TEM foils. A dual beam (electron beam + ion beam) Focused Ion Beam (FIB) will be used to remove TEM foils at precisely designated locations within the welds. This will greatly improve the chances of obtain-ing a foil with the desired microstructural information. Diffraction contrast techniques will be used on a Philips CM 200 and CM 300 Field Emission Gun TEMs to determine the details of the deformation processes, i.e., the development of deformation substructure (e.g., sub-grains and sub-bands), the occurrence of dynamic recovery and recrystallization, annealing effects, and phase transformations. Scanning electron microscopy will be performed on a Philips XL-30 FEG instrument using Orientation Imaging Microscopy to reveal possible microtexture that may be residual from the base material. The results of these microstructural studies will be used to complement process optimization and mechanical property data.%%% This is a research enhancement grant made under the Professional Opportunities for Women in Research and Education (POWRE) program. The PI plans to realign her career after a four-year hiatus in an administrative capacity. Prior to working as Aerospace Team Leader at Edison Welding Institute and Associate Director for the Center for the Accelerated Maturation of Mate-rials (CAMM) at the Ohio State University, she led an active technical career for 15 years. The research is expected to contribute basic materials science knowledge at a fundamental level of special relevance to the behavior of metals. The project is co-supported by the Division of Mate-rials Research, and the MPS OMA(Office of Multidisciplinary Activities). ***

该项目旨在更好地了解钛合金搅拌摩擦焊缝的高温变形和微观结构演变的基本机制。选择了两种合金，纯（CP）钛和Ti-6Al-4V，a + b合金。 CP 钛因其耐腐蚀性而被广泛使用，特别是在化学加工工业中，因其良好的成型性而被选中。 Ti-6Al-4V 广泛应用于各种航空航天和船舶应用的焊接和非焊接条件下。除了“正常”焊接之外，还将评估间断焊接，即工具在到达待连接的两块板的末端之前缩回的情况。通过这种方式，热机械影响区和热影响区的微观结构将与焊缝之前的材料进行比较。这些反过来将与搅拌区（实际动态再结晶焊缝）和母材的微观结构进行比较。将获取样品进行横向和纵向金相检查，以揭示每个不同的微观结构区域，并作为 TEM 箔的最终位置图。双束（电子束 + 离子束）聚焦离子束 (FIB) 将用于去除焊缝内精确指定位置的 TEM 箔。这将大大提高获得具有所需微观结构信息的箔的机会。衍射对比技术将用于飞利浦 CM 200 和 CM 300 场发射枪 TEM，以确定变形过程的细节，即变形子结构（例如亚晶粒和子带）的发展、动态变形的发生回复和再结晶、退火效应和相变。将使用定向成像显微镜在飞利浦 XL-30 FEG 仪器上进行扫描电子显微镜检查，以揭示基材中可能残留的微观纹理。这些微观结构研究的结果将用于补充工艺优化和机械性能数据。%%% 这是根据女性研究和教育专业机会 (POWRE) 计划提供的研究增强补助金。在担任行政职务四年后，PI 计划重新调整自己的职业生涯。在担任爱迪生焊接研究所航空航天团队组长和俄亥俄州立大学材料加速成熟中心 (CAMM) 副主任之前，她从事了 15 年积极的技术职业生涯。该研究预计将在与金属行为特别相关的基础水平上贡献基础材料科学知识。该项目得到了材料研究部和MPS OMA（多学科活动办公室）的共同支持。 ***