CAREER: Understanding the origins of pearlite discontinuities in eutectoid microstructures: Modeling & Experiments

职业：了解共析微观结构中珠光体不连续性的起源：建模

• 批准号: 2145812
• 负责人: Kumar Ankit
• 金额: $ 56.03万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2027-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2145812&HistoricalAwards=false
• 关键词: CAREER; Understanding; origins; pearlite; discontinuities

PART 1: NON-TECHNICAL SUMMARY There are many different types of steels and several ways to categorize them. One way to group them is according to the types of structures one sees when looking closely at them under a microscope. Scientists who study metals call these structures that are only visible at extremely high magnification, "microstructures". "Pearlite" or "Pearlitic microstructures" are a type of steel that has a layered microstructure that is hard and strong and is commonly used in applications that require high strength such as railroads, drawbridge support cables, and cutting tools. However, in many other applications, steel needs to be softened before they can be formed or machined into complex shapes. Although steels have been used and studied for many generations, understanding how different processing conditions specifically impact steel microstructure is somewhat limited, particularly in commercial steels where complex chemical compositions make understanding what is occurring on an atomic level difficult. This CAREER award, which integrates computational, experimental, and characterization techniques, will allow for an organized study examining breaks in the layered microstructures of Pearlitic steels and the atomic interactions that produce them. Specifically, this study will use heating and cooling experiments on model steels containing only three of four elements (Fe, Carbon and Manganese or Silicon) in conjunction with computer simulations and advanced 2D, 3D and 4D (3D through time) imaging to investigate the relationship between how materials are made and what microstructures they come to possess. Establishing these relationships will enable microstructure level control in the manufacturing of steel components, which is currently a missing bit of knowledge in steel-making. The outreach component of this project addresses the pressing need to bridge the vast gap between materials research and national annual enrollment shortages in Materials Science and Engineering (MSE). In pursuit of this goal, this project encourages students at all levels to pursue education and careers in MSE fields through student-centric communication that incorporates active learning. This approach, which can help address many community-specific needs for underrepresented populations will be incorporated into a tailored outreach plan for high-school, undergraduate and graduate students.PART 2: TECHNICAL SUMMARYSteel microstructures consisting of lamellar pearlite are known to possess high tensile strength, excellent toughness, and hardness due to their layered microstructure. However, to enhance the formability of such microstructures, steel must be softened, which is typically accomplished via annealing heat treatments that facilitate the spheroidization or non-cooperative evolution of pearlite. The addition of alloying elements, such as Manganese and Silicon can also impact pearlite spheroidization, leading to lamellar discontinuities and improved ductility. Unfortunately, current understanding of the mechanisms by which pearlitic discontinuities arise and how they are influenced by alloy composition, processing temperature, prior austenite grain size, and dislocation densities leave much to be desired. While comprehending multi-component diffusion and pearlitic microstructural evolution during processing is challenging, it is a necessary step to exert greater control on microstructure which ultimately determines mechanical properties. Since the evolution of phase morphologies cannot be predicted through experiments or numerical calculations in isolation, the development of an integrated approach, that combines phase-field models with experiments, characterization, and microstructure quantification is required to better understand processing-microstructure relations. To integrate and leverage existing hi-fidelity tools, this CAREER award tests the hypothesis that discontinuous growth of pearlitic lamellae in steel microstructures occur by a non-cooperative mechanism. To examine this hypothesis, computational and annealing studies of ternary Fe-C-Mn and Fe-C-Si steels will be complemented by advanced characterization techniques such as X-ray Computed Tomography, Analytical Transmission Electron Microscopy leveraging Energy Dispersive Spectroscopy, and Electron Backscatter Diffraction. While a comparison of simulated and characterized microstructures using spatial correlation functions will facilitate a basic understanding of the mechanisms that induce lamellar discontinuities in pearlitic microstructures, processing-microstructure linkages will be deduced through Principal Component Analyses of the obtained datasets. The broader impacts of this project exist in two parts. The first is the development and free dissemination of an integrated experimental, computational and four-dimensional characterization protocol for lamellar discontinuities in steels. The second leverages the technical research of this project to deploy student-centric education and outreach programs using active learning realized in four segments of activity: (i) undergraduate and high-school “Idol” programs, (ii) undergraduate research, (iii) undergraduate and graduate course development, and (iv) remote phase-field workshops.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.

有许多不同类型的钢和几种对它们进行分类的方法。对它们进行分类的一种方法是根据在显微镜下仔细观察它们时所看到的结构类型。研究金属的科学家把这些只有在极高倍率下才能看到的结构称为“微结构”。“珠光体”或“珠光体微结构”是一种具有层状微结构的钢，硬度高，强度大，通常用于要求高强度的应用，如铁路，吊桥支撑电缆和切削工具。然而，在许多其他应用中，钢在成型或加工成复杂的形状之前需要软化。尽管钢铁已经被使用和研究了许多代，但了解不同的加工条件如何具体影响钢的微观结构在某种程度上是有限的，特别是在复杂的化学成分使得理解原子水平上发生的事情变得困难的商业钢中。该奖项整合了计算、实验和表征技术，将允许对珠光体钢层状微观结构中的断裂和产生它们的原子相互作用进行有组织的研究。具体来说，本研究将对仅含四种元素（铁、碳、锰或硅）中的三种元素的模型钢进行加热和冷却实验，并结合计算机模拟和先进的2D、3D和4D （3D through time）成像，研究材料的制造方式与它们拥有的微观结构之间的关系。建立这些关系将使钢构件制造中的微观结构水平控制成为可能，这是目前炼钢中缺少的一点知识。该项目的外展部分解决了弥合材料研究与国家材料科学与工程（MSE）年度招生短缺之间巨大差距的迫切需要。为了实现这一目标，该项目鼓励各级学生通过以学生为中心的交流，结合主动学习，在MSE领域追求教育和职业。这种方法可以帮助解决代表性不足人口的许多社区特定需求，将被纳入针对高中、本科生和研究生的量身定制的外展计划。第2部分：技术概述由层状珠光体组成的钢微观结构由于其层状微观结构而具有高抗拉强度、优异的韧性和硬度。然而，为了提高这种微观组织的成形性，必须对钢进行软化，这通常是通过退火热处理来实现的，从而促进珠光体的球化或非协同演化。添加合金元素，如锰和硅，也会影响珠光体球化，导致片层不连续，提高延展性。不幸的是，目前对珠光体不连续产生的机制以及它们如何受到合金成分、加工温度、先前奥氏体晶粒尺寸和位错密度的影响的理解还有很多需要改进的地方。虽然在加工过程中理解多组分扩散和珠光体组织演变具有挑战性，但这是对微观组织进行更大控制的必要步骤，而微观组织最终决定了材料的力学性能。由于相形态的演变不能通过孤立的实验或数值计算来预测，因此需要开发一种将相场模型与实验、表征和微观结构量化相结合的综合方法，以更好地理解加工-微观结构之间的关系。为了整合和利用现有的高保真工具，本CAREER奖验证了钢微观组织中珠光体片的不连续生长是由非合作机制发生的假设。为了验证这一假设，对三元Fe-C-Mn和Fe-C-Si钢的计算和退火研究将辅以先进的表征技术，如x射线计算机断层扫描、利用能量色散光谱的分析透射电子显微镜和电子背散射衍射。虽然使用空间相关函数对模拟和表征的微观结构进行比较将有助于对珠光体微观结构中引起层状不连续性的机制的基本理解，但通过获得的数据集的主成分分析将推断出加工-微观结构的联系。这个项目的更广泛的影响存在于两个方面。第一个是发展和自由传播的综合实验，计算和四维表征协议的片层不连续钢。第二个是利用该项目的技术研究来部署以学生为中心的教育和推广计划，利用在四个活动部分实现的主动学习：(i)本科和高中“偶像”计划，（ii）本科研究，（iii）本科和研究生课程开发，以及（iv）远程相场研讨会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Emulating microstructural evolution during spinodal decomposition using a tensor decomposed convolutional and recurrent neural network

• DOI: 10.1016/j.commatsci.2023.112187
• 发表时间: 2023-05
• 期刊: Computational Materials Science
• 影响因子: 3.3

Phase-field modeling of nanostructural evolution in physical vapor deposited phase-separating ternary alloy films

物理气相沉积相分离三元合金薄膜纳米结构演化的相场建模

• DOI: 10.1088/1361-651x/aca03f
• 发表时间: 2022
• 期刊: Modelling and Simulation in Materials Science and Engineering
• 影响因子: 1.8
• 作者: Raghavan, Rahul;Wu, Peichen;Ankit, Kumar
• 通讯作者: Ankit, Kumar

Emulating the evolution of phase separating microstructures using low-dimensional tensor decomposition and nonlinear regression

• DOI: 10.1557/s43577-022-00443-x
• 发表时间: 2023-01
• 期刊: MRS Bulletin
• 影响因子: 5
• 作者: A. Iquebal;Peichen Wu;A. Sarfraz;K. Ankit