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

• 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

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.

非技术性总结：该项目将使用最先进的设备，利用高能同步加速器X射线进行超高速成像，以了解金属和合金凝固过程中的热裂纹问题。热裂意味着，在铸造或3D打印过程中没有获得完全固态的金属，而是留下了削弱材料的裂纹。 这也可能意味着破裂的部件必须被丢弃和/或修整，这是浪费的。 主要重点将是研究激光3D打印过程中的裂纹，其中兆赫兹成像提供了微秒级的分辨率，这种分辨率最为人所知的是子弹穿透装甲的定格电影。近年来，由于新相机的出现和X射线检测的改进，这种超高速成像技术取得了迅速进展，并为我们理解熔化过程做出了重大贡献。因此，它非常适合对裂缝的突然发生和生长进行成像。将研究裂纹对凝固速度和化学成分变化的敏感性。计算机模拟将被用来测试关于材料微观结构如何发生开裂的假设。在这项工作中获得的新认识在整个铸造行业中具有广泛的影响。它还可能激发对问题的新的理论分析，这通常发生在应用新的实验技术时。除了支持一名博士生外，还将招募本科生协助这项工作，其中包括对图像序列进行大量详细分析。这项工作还将传播给20多家公司，这些公司是CMU NextManufacturing Center的成员，对增材制造有着强烈的直接兴趣。随着分析的进行，主要结果将被纳入PI的教学中，这将有助于确保CMU的MS和增材制造工程辅修课程保持最新。技术概要：该提案将使用超快X射线显微镜，高能量，高强度同步加速器X射线，来测试凝固裂纹的成核是可变的，并取决于接近冷冻过程结束时固体形态的假设。由于缺乏直接测量的成核点和任意方面的成核开裂理论，即使是测量的固体分数在开裂开始将是新颖的。测量裂纹的成核程度取决于柱状与等轴生长的程度，将进一步扩展我们对这个问题的基本知识。我们还将探测裂纹的非均质成核，例如，在铝基合金的激光熔化中经常观察到的小气泡。预期的结果包括在各种材料中作为温度梯度和冷却速率的函数的凝固裂纹的直接可视化，这些温度梯度和冷却速率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铝合金容易开裂，部分原因是为了便于成像，与不锈钢或镍合金进行比较。我们还将使用格子玻尔兹曼模拟（来自以前的DMREF项目）来模拟凝固并量化糊状区，特别是高固体分数下液体区的形状。最直接的影响将是激光粉末床打印，但对铸造技术也存在更广泛的影响。通过合作，我们将寻求获得不同类型的改性粉末，以避免开裂，例如，促进等轴显微组织。我们将使用计算机断层扫描和切片进行3D表征。超快X射线显微镜将主要在高级光子源进行，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的法定使命，并通过使用该基金会的评估被认为值得支持智力优点和更广泛的影响审查标准。

项目成果

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

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

• DOI: 10.1016/j.addma.2021.101959
• 发表时间: 2021-06-01
• 期刊: ADDITIVE MANUFACTURING
• 影响因子: 11
• 作者: Kouraytem, Nadia;Chiang, Po-Ju;Rollett, Anthony D.
• 通讯作者: Rollett, Anthony D.

The influence of processing and texture on the grain boundary character distribution of an austenitic Ni 30Fe alloy

加工和织构对奥氏体Ni 30Fe合金晶界特征分布的影响

• DOI: 10.1016/j.matchar.2023.112708
• 发表时间: 2023
• 期刊: Materials Characterization
• 影响因子: 4.7
• 作者: Beladi, Hossein;Chao, Qi;Tari, Vahid;Rollett, A.D.;Rohrer, Gregory S.
• 通讯作者: Rohrer, Gregory S.

An Updated Index Including Toughness for Hot-Cracking Susceptibility

• DOI: 10.1007/s11661-022-06612-6
• 发表时间: 2022-02
• 期刊: Metallurgical and Materials Transactions A
• 作者: Guannan Tang;Benjamin J. Gould;Abigail Ngowe;A. Rollett