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

本项目旨在更好地理解钛合金搅拌摩擦焊高温变形和微观组织演变的基本机制。选择了两种合金，纯钛（CP）和Ti-6Al-4V，a + B合金。CP钛，用于其耐腐蚀性，特别是在化学加工工业中，被选为其良好的成形性。Ti-6Al-4V广泛用于焊接和非焊接条件下的各种航空航天和海洋应用。除了“正常”焊缝外，还将评估间断焊缝，即工具在到达待连接的两块板的端部之前缩回。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接前的材料进行比较。这些又将与搅拌区（实际动态再结晶焊缝）和基材的显微组织进行比较。将在横向和纵向方向上获得用于金相检查的样品，以揭示每个不同的微观结构区域，并作为TEM箔的最终位置的地图。将使用双束（电子束+离子束）聚焦离子束（FIB）在焊缝内的精确指定位置去除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。将在Philips CM 200和CM 300场发射枪TEM上使用衍射对比技术来确定变形过程的细节，即，变形子结构的发展（例如，亚晶粒和亚带）、动态回复和再结晶的发生、退火效应和相变。将使用方向成像显微镜在Philips XL-30 FEG仪器上进行扫描电子显微镜检查，以显示可能残留自基材的可能微观纹理。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。%这是根据研究和教育领域妇女专业机会方案提供的一项研究增强补助金。PI计划在行政能力中断四年后重新调整她的职业生涯。在担任爱迪生焊接研究所航空航天团队负责人和俄亥俄州州立大学材料加速成熟中心（CAMM）副主任之前，她领导了15年的积极技术职业生涯。该研究有望在与金属行为特别相关的基础层面上贡献基础材料科学知识。该项目由材料研究部和MPS OMA（多学科活动办公室）共同支持。***

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). ***