Fast X-ray Microscopy to Quantify the Nucleation of Hot Cracking

快速 X 射线显微镜量化热裂纹成核

基本信息

批准号：
1905910
负责人：
Anthony Rollett
金额：
$ 50.01万
依托单位：
Carnegie-Mellon University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-09-01 至 2023-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1905910&HistoricalAwards=false
关键词：
Fast ray Microscopy Quantify Nucleation

项目摘要

NON-TECHNICAL SUMMARY: This project will use state-of-the-art facilities for ultra-high speed imaging with high energy synchrotron x-rays for the purpose of understanding the problem of hot cracking during the solidification of metals and alloys. Hot cracking means that, instead of obtaining fully solid metal during casting or 3D printing, cracks are left behind that weaken the material. It may also mean that the cracked component must be discarded and/or trimmed, which is wasteful. The main focus will be on studying cracking during 3D printing with laser light where mega-Hertz imaging provides micro-second resolution of the sort best known for stop-action movies of bullets penetrating through armor. Such ultra-high speed imaging has made rapid progress in recent years thanks to the advent of new cameras and improvements in x-ray detection and has already made substantial contributions to our understanding of the melting process. It is thus extremely well suited to imaging the sudden onset and growth of cracks. The sensitivity of cracking to variations in solidification speed and chemical composition will be investigated. Computer simulation will be used to test hypotheses about how the cracking happens with respect to the materials microstructure. The new understanding gained in this work has broad impacts in the casting industry in general. It is also likely to stimulate new theoretical analysis of the problem, which often happens when a new experimental technique is applied. In addition to supporting a doctoral student, undergraduates will be recruited to assist with the work, which involves a good deal of detailed analysis of sequences of images. The work will also be disseminated to the twenty-plus companies that are members of CMU's NextManufacturing Center and have a strong direct interest in additive manufacturing. As the analysis proceeds, the main results will be incorporated into the PI's teaching, which will help ensure that CMU's MS and engineering minor programs in additive manufacturing stay up to date.TECHNICAL SUMMARY:This proposal will use ultra-fast x-ray microscopy, with the high energy, high intensity synchrotron x-rays, to test the hypothesis that the nucleation of solidification cracking is variable and depends on the morphology of the solid near the end of the freezing process. Given the lack of direct measurement of the nucleation point and the arbitrary aspect of nucleation in cracking theories, even a measurement of the solid fraction at which cracking starts will be novel. Measuring the degree to which the nucleation of cracking depends on the extent of columnar versus equiaxed growth will further extend our fundamental knowledge of the problem. We will also probe for heterogeneous nucleation of the cracks from, e.g., the small vapor bubbles that are often observed in laser melting of Al-based alloys. The expected results include direct visualization of solidification cracking in a variety of materials as a function of temperature gradient and cooling rate, which are controlled by laser power and scan speed. We will mainly focus on aluminum alloys, partly because many of the structural Al alloys are prone to cracking and partly for ease of imaging, with stainless steel or nickel alloys for comparison purposes. We will also use lattice-Boltzmann simulations (from a previous DMREF project) to model the solidification and quantify the mushy zone, specifically the shape of the liquid zones at high solid fractions. The most direct impact will be on laser powder bed printing but the potential for broader impact on casting technologies also exists. Through collaboration, we will seek access to different types of modified powders that are intended to avoid cracking through, e.g., promoting equiaxed microstructures. We will use computed tomography and sectioning for 3D characterization. The ultra-fast x-ray microscopy will be mostly carried out at the Advanced Photon Source because this facility has the best combination of high energy and intensity.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.

非技术摘要：该项目将使用最先进的设施进行超高速度成像，并使用高能量同步器X射线射线进行超高速度成像，以了解金属和合金固化过程中热开裂的问题。热开裂意味着，裂纹不会在铸造或3D打印过程中获得完全固体金属，而是留下裂缝，从而削弱了材料。这也可能意味着必须丢弃和/或修剪破裂的组件，这是浪费的。主要的重点将是在3D打印过程中使用激光光研究裂纹，其中Mega-Hertz成像提供了微小的分辨率，即以穿透装甲穿透的子弹电影而闻名的那种。由于新相机的出现和X射线检测的改进，这种超高速度成像近年来取得了迅速的进步，并且已经为我们对熔化过程的理解做出了重大贡献。因此，它非常适合成像裂纹的突然发作和生长。将研究开裂对固化速度和化学成分变化的敏感性。计算机模拟将用于测试有关材料微结构如何发生裂纹的假设。这项工作中获得的新理解对总体上的铸造行业产生了广泛的影响。它也可能刺激问题的新理论分析，这通常是在应用新的实验技术时发生的。除了支持博士生外，还将招募本科生来协助这项工作，这涉及大量对图像序列的详细分析。这项工作还将被传播给21多家公司，这些公司是CMU Next制造中心的成员，并对增材制造具有强烈的直接兴趣。随着分析的进行，主要结果将纳入PI的教学中，这将有助于确保CMU的MS和工程辅助制造中的次要计划保持最新。技术摘要：该建议将使用Ultra-Fast X射线显微镜，使用高能量，高强度同步子X射线，以检验固化裂纹成核的假设是可变的，并取决于固体在冷冻过程结束时的形态。鉴于缺乏对成核点的直接测量和破裂理论中成核的任意方面，即使是对开裂开始的固体分数的测量也将是新颖的。衡量裂纹成核的程度取决于柱状和等亚生长的程度，将进一步扩展我们对问题的基本知识。我们还将探测裂纹的异质成核，例如，在基于Al的合金的激光熔融中经常观察到的小型蒸气气泡。预期的结果包括直接可视化多种材料中的固化破裂，这是温度梯度和冷却速率的函数，这些均由激光功率和扫描速度控制。我们将主要关注铝合金，部分原因是许多结构合金容易裂纹，部分用于易于成像，并具有不锈钢或镍合金以进行比较。我们还将使用格子玻尔兹曼模拟（从以前的DMREF项目）来对固化进行建模并量化糊状区域，特别是在高固体馏分下液体区域的形状。最直接的影响是对激光粉床的印刷，但对铸造技术产生更广泛影响的潜力也存在。通过协作，我们将寻求访问旨在避免破解的不同类型的修改后的粉末，例如促进等上的微观结构。我们将使用计算机断层扫描和切片进行3D表征。超快速的X射线显微镜将主要是在高级光子源进行的，因为该设施具有高能量和强度的最佳组合。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力来评估的支持的。优点和更广泛的影响审查标准。

项目成果

期刊论文数量（5）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

High frequency beam oscillation keyhole dynamics in laser melting revealed by in-situ x-ray imaging

DOI：
10.1038/s43246-023-00332-z
发表时间：
2023-02
期刊：
Communications Materials
影响因子：
7.8
作者：
Ziheng Wu;Guannan Tang;S. Clark;A. Meshkov;S. Roychowdhury;Benjamin J. Gould;V. Ostroverkhov;
通讯作者：
Ziheng Wu;Guannan Tang;S. Clark;A. Meshkov;S. Roychowdhury;Benjamin J. Gould;V. Ostroverkhov;

Solidification crack propagation and morphology dependence on processing parameters in AA6061 from ultra-high-speed x-ray visualization