14 31 48 P. 28 MAY/JUNE 2023 | VOL 181 | NO 4 Advancing Di usion Bonded Heat Exchangers ASM Reference Publications & Digital Databases Catalog HTPro Newsletter Included in This Issue FRACTURE ANALYSIS IN ARCHAEOMETALLURGICAL METALS MATERIALS TESTING/CHARACTERIZATION
14 31 48 P. 28 MAY/JUNE 2023 | VOL 181 | NO 4 Advancing Di usion Bonded Heat Exchangers ASM Reference Publications & Digital Databases Catalog HTPro Newsletter Included in This Issue FRACTURE ANALYSIS IN ARCHAEOMETALLURGICAL METALS MATERIALS TESTING/CHARACTERIZATION
heattreatevent.org REGISTRATION NOW OPEN! Heat Treat is the premier conference and expo for heat treating professionals, attracting international innovators, researchers, influencers, and decision makers from around the globe. Co-located with IMAT 2023 and Motion + Power Technology Expo, Heat Treat attendees can access the POWER of three events in ONE location, o ering MORE content, MORE attendees, MORE networking, and MORE ROI, including: • 450 Technical Presentations, Keynotes, and Special Sessions • 5000 Attendees • 400 Exhibitors Don’t miss out on attending the largest conference and expo in North America dedicated to heat treating! 32ND HEAT TREATING SOCIETY CONFERENCE AND EXHIBITION OCTOBER 17–19, 2023 | HUNTINGTON PLACE | DETROIT, MICHIGAN ORGANIZED BY: CO-LOCATED WITH: DRIVING THE FUTURE OF THERMAL PROCESSING heattreatevent.org Register today!
59 ASM NEWS The latest news about ASM members, chapters, events, awards, conferences, affiliates, and other Society activities. ADVANCING DIFFUSION BONDED COMPACT HEAT EXCHANGERS FOR HIGH TEMPERATURE APPLICATIONS Mohamed Elbakhshwan, Lukas Desorcy, Ian Jentz, Mark Anderson, Fei Gao, Todd Allen, Mark Messner, Mike McMurtrey, Jim Stubbins, John Shingledecker, Billy Nollet, Bob Keating, and Suzanne McKillup Enhancement of the diffusion bonding process for the development of compact heat exchangers provides an energy efficient solution for high-temperature applications in advanced nuclear reactors and other technologies. 14 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 2 Restoration of a 13th century Khan cup involved piecing together 154 fragments. Published in ASM Handbook, Volume 12, Fractography and original image courtesy of Gerhard Stawinoga, Archaeological Landesmuseum, University of Kiel, Schloß Gottorf, Schleswig, Germany. On the Cover: 72 3D PRINTSHOP Winners of the AMUG Technical Competition and researchers who are using an inverse design method to print porous surfaces. 23 ALUMINUM APPLICATIONS IN MARINE TRANSPORTATION Robert Sanders and Graeme Marshall Beyond weight savings, aluminum products offer corrosion resistance, weldability, and ease of maintenance for a wide range of marine vessels.
4 Editorial 5 Research Tracks 5 Feedback 10 Machine Learning 6 Metals/Polymers/Ceramics 8 Testing/Characterization 11 Process Technology 12 Emerging Technology 13 Sustainability 71 Editorial Preview 71 Special Advertising Section 71 Advertisers Index 72 3D PrintShop TRENDS INDUSTRY NEWS DEPARTMENTS Check out the Digital Edition online at asminternational.org/news/magazines/am-p ASM International serves materials professionals, nontechnical personnel, and managers wordwide by providing high-quality materials information, education and training, networking opportunities, and professional development resources in cost-effective and user-friendly formats. ASM is where materials users, producers, and manufacturers converge to do business. Advanced Materials & Processes (ISSN 0882-7958, USPS 762080) publishes eight issues per year: January/February, March, April, May/June, July/August, September, October, and November/December, by ASM International, 9639 Kinsman Road, Materials Park, OH 44073-0002; tel: 440.338.5151; fax: 440.338.4634. Periodicals postage paid at Novelty, Ohio, and additional mailing offices. Vol. 181, No. 4, MAY/JUNE 2023. Copyright © 2023 by ASM International®. All rights reserved. Distributed at no charge to ASM members in the United States, Canada, and Mexico. International members can pay a $30 per year surcharge to receive printed issues. Subscriptions: $499. Single copies: $54. POSTMASTER: Send 3579 forms to ASM International, Materials Park, OH 44073-0002. Change of address: Request for change should include old address of the subscriber. Missing numbers due to “change of address” cannot be replaced. Claims for nondelivery must be made within 60 days of issue. Canada Post Publications Mail Agreement No. 40732105. Return undeliverable Canadian addresses to: 700 Dowd Ave., Elizabeth, NJ 07201. Printed by LSC Communications, Lebanon Junction, Ky. 19 ARCHAEOMETALLURGICAL STUDY OF ARGENTINIAN RAILWAY PARTS Patricia Silvana Carrizo Analysis of two historical railway parts reveals the techniques and treatments used on these metals that helped them endure centuries of use. 28 ARCHAEOMETALLURGICAL FRACTURE ANALYSIS Russell Wanhill and Omid Oudbashi Case studies demonstrate the benefits of employing fractographic analysis to study cracking and fracture mechanisms in heritage alloys. 31 ASM REFERENCE PUBLICATIONS & DIGITAL DATABASES CATALOG Our vast, authoritative reference library offers the most comprehensive and up-to-date materials information. FEATURES MAY/JUNE 2023 | VOL 181 | NO 4 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 3 19 31 48 28 48 HTPro The official newsletter of the ASM Heat Treating Society (HTS). This supplement focuses on heat treating technology, processes, materials, and equipment, along with HTS news and initiatives.
4 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 ASM International 9639 Kinsman Road, Materials Park, OH 44073 Tel: 440.338.5151 • Fax: 440.338.4634 Joanne Miller, Editor email@example.com Victoria Burt, Managing Editor firstname.lastname@example.org Frances Richards and Corinne Richards Contributing Editors Anne Vidmar, Layout and Design Allison Freeman, Production Manager email@example.com Press Release Editor firstname.lastname@example.org EDITORIAL COMMITTEE Adam Farrow, Chair, Los Alamos National Lab John Shingledecker, Vice Chair, EPRI Somuri Prasad, Past Chair, Sandia National Lab Beth Armstrong, Oak Ridge National Lab Margaret Flury, Medtronic Surojit Gupta, University of North Dakota Nia Harrison, Ford Motor Company Michael Hoerner, KnightHawk Engineering Hideyuki Kanematsu, Suzuka National College of Technology Ibrahim Karaman, Texas A&M University Ricardo Komai, Tesla Bhargavi Mummareddy, Dimensional Energy Scott Olig, U.S. Naval Research Lab Christian Paglia, SUPSI Institute of Materials and Construction Amit Pandey, Lockheed Martin Space Satyam Sahay, John Deere Technology Center India Kumar Sridharan, University of Wisconsin Jean-Paul Vega, Siemens Energy Vasisht Venkatesh, Pratt & Whitney ASM BOARD OF TRUSTEES David B. Williams, President and Chair Pradeep Goyal, Senior Vice President Navin Manjooran, Vice President Judith A. Todd, Immediate Past President John C. Kuli, Treasurer Burak Akyuz Amber Black Ann Bolcavage Pierpaolo Carlone Elizabeth Homan Toni Marechaux André McDonald U. Kamachi Mudali James E. Saal Sandra W. Robert, Executive Director STUDENT BOARD MEMBERS Jaime Berez, Ashlie Hamilton, Nicole Hudak Individual readers of Advanced Materials & Processes may, without charge, make single copies of pages therefrom for personal or archival use, or may freely make such copies in such numbers as are deemed useful for educational or research purposes and are not for sale or resale. Permission is granted to cite or quote from articles herein, provided customary acknowledgment of the authors and source is made. The acceptance and publication of manuscripts in Advanced Materials & Processes does not imply that the reviewers, editors, or publisher accept, approve, or endorse the data, opinions, and conclusions of the authors. IMAGING ACROSS TIME Metallographers often describe their craft as a magical place where art meets science. In this issue, we provide a spectrum of how imaging has been utilized in materials science, for both unveiling the past and predicting the future. We start off with two archaeometallurgy articles that take us on trips to earlier times. One presents the study of bolts and nails from a railroad track in Argentina built in the late 19th century. The author’s micrographs tell the story of how the parts were manufactured to withstand dynamic loads for more than a century of use. Another article offers case studies of fractures in museum artifacts containing gold and silver. Fractographic analysis was employed to determine the best restoration method for each precious item. Enter artificial intelligence (AI). Now art and science, powered by AI, opens up whole new possibilities. In April, Sandvik Coromant unveiled a sculpture their engineers created using AI and advanced digital manufacturing techniques by fusing together works from five iconic sculptors over the past 500 years, including Michelangelo. Carved out of stainless steel, the “Impossible Statue” crosses time and space and was brought together by today’s extraordinary technologies. The modern artwork, highlighting old masters through new AI tools, is on display at Sweden’s National Museum of Science and Technology. For more on the astounding uses of AI in image creation and analysis, see the Machine Learning page in this issue. We’ve previously published articles on the use of computer vision and machine learning to provide detailed data on micrographs. But the tools continue to get more sophisticated. As one example, complete image analysis now can be delivered by the software AtomAI from images gathered from electron and scanning probe microscopy. The technology frees up a metallographer to spend time studying the derived datasets and coming to deeper conclusions. As a modeling tool, AI can also be predictive in imagining how a micrograph would change given a different dataset. Surprisingly, images now can be created simply from text prompts, like giving ChatGPT a command. These newer diffusion models of AI use their accumulated knowledge of the subject matter to create an image from scratch. That’s going a step beyond an AI tool that simply finds an existing image and adds new details to it. AI will continue to develop, and it will be used. A recent study by Deloitte indicated that in 2023 more than half of all organizations plan to integrate AI technologies and automation into their processes. It will be important for us to learn along the way about the new capabilities for imaging as well as other applications, while being on alert for bad actors. AI poses risks but there are also massive advantages. Tapping into those advantages, just imagine how metallographers will image and analyze our 2023 artifacts in the future. I hope it’s magical. email@example.com Sandvik’s AI-generated, stainless steel statue.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 5 GRAIN BOUNDARY ENGINEERING PROGRESS Researchers from the Max Planck Institute for Iron Research (MPIE), Germany, along with colleagues from Northwestern University and the Leibniz Institute for Solid State and Materials Research Dresden, recently tuned the microstructure of thermoelectric materials by doping the grain boundaries with titanium. Because thermoelectric materials are being considered for power generation—to transform waste heat into electricity—the team’s goal was to modify the grain boundaries so that only thermal conductivity is reduced, while electrical conductivity remains high. The scientists used a Ti-doped NbFeSb half-Heusler intermetallic compound, a new and promising thermoelectric alloy. It has excellent thermoelectric properties at mid to high temperatures, good thermal and mechanical robustness, and its elements are abundant. Because the grain size is small, the increased number of grain boundaries significantly reduces electrical conductivity. “By doping the alloy with titanium, we found that grain boundaries become titanium-rich and no longer resistive, so that we can fully utilize the beneficial low RESEARCH TRACKS / FEEDBACK The titanium-rich grain boundary phase provides a conductive path (left), while the iron-rich grain boundary phase is resistive to electrons (right). Courtesy of MPIE. thermal conductivity provided by the small grain size,” explains researcher Siyuan Zhang. After demonstrating the strategy of grain boundary engineering, the team is now exploring new ways to selectively dope these boundaries. www.mpie.de. MAKING MORE SENSE OF MOFs A new study from the University of Pittsburgh Swanson School of Engineering (Pitt) shows that metal-organic frame- works (MOFs) heat up substantially when they soak up gases—and if they get too hot, they quit working. “This study helps us determine which MOFs can soak up gases and dissipate that heat efficiently, ultimately moving MOFs closer to practical commercial implementation,” says researcher Chris Wilmer, associate professor of chemical and petroleum engineering. Researchers used computational screening of thermal conductivity in over 10,000 MOFs, a task that required more than a million hours of supercomputing power. They learned that MOFs with high densities, small pores, and 4-connected metal nodes are more capable of conducting heat. Conversely, those with extremely large pores are not. Wilmer and his colleagues, including researchers from Pitt, Colorado School of Mines, Carnegie Mellon University, and the University of California, Berkeley, are focusing on designing MOFs with excellent thermal properties. “There are millions of different types of MOFs one can design, so it can be hard to determine the best one for the job,” says Pitt researcher Meiirbek Islamov. “This study allows us to be more accurate as we create them in a lab.” www.engineering.pitt.edu. SIZING ERRATUM The news item “Measuring Thin Skin of Calcium Nuclei” in the March 2023 issue of AM&P stated that a femtometer is “just one billionth of a meter.” A femtometer is actually 10-15 m, or one quadrillionth of a meter. Kirk Cooper Worthington Industries Editor’s Note: We regret not catching the error that appeared on the original Department of Energy press release used as source material. We have notified them. FEEDBACK We welcome all comments and suggestions. Send letters to firstname.lastname@example.org. Building blocks used to build 10,194 hypothetical MOFs containing 1015 topologies. Courtesy of npj Computational Materials, 2023.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 6 METALS | POLYMERS | CERAMICS The DOE’s Office of Energy Efficiency and Renewable Energy will renew funding for its Institute for Advanced Composites Manufacturing Innovation (IACMI), one of DOE’s six Clean Energy Manufacturing Innovation Institutes. IACMI will receive federal funding for five fiscal years, with a first-year investment of $6 million. This builds on initial DOE funding of $70 million and over $180 million from IACMI’s member partners. energy.gov. A new steel called “Military-Steel” from AMD Corp., Toronto, reportedly features the same impact toughness as USAF-96 steel at higher strength, while its raw material cost is 25-35% lower. Due to its high strength and high impact toughness, the newly designed steel could be a good candidate for use in automotive gears and powertrain components as well as in military applications such as cases for deep penetrating bombs. For more information, email email@example.com. BRIEFS parts failure. In particular, the products had no signs of large metal clusters— impurities that can cause material deterioration and have hampered efforts to use secondary recycled aluminum to make new products. The patented ShAPE technology is available for licensing for other applications. pnnl.gov, magna.com. SOURCING RARE EARTH ELEMENTS FROM WASTE A team of researchers at Washington University, St. Louis, developed a method to extract rare earth elements (REEs) from coal fly ash—a fine, powdery waste product from the combustion of coal. The researchers say their process is ultimately a pathway toward reduction and remediation of waste products. With more than 79 million metric tons of coal fly ash generated in the U.S. annually, the team reports that the potential value of the REEs that could be extracted is estimated at more than $4 billion per year. The novel extraction process uses supercritical fluid, commonly used to decaffeinate coffee, to recover critically needed REEs from material that would otherwise be discarded in a landfill. The team’s work is the first to show that common and accessible supercritical fluids, including carbon dioxide, nitrogen, and air, were able to extract RECYCLING ALUMINUM FOR EV PARTS An innovative manufacturing process that collects and transforms scrap aluminum directly into new vehicle parts was unveiled by collaborators from the DOE’s Pacific Northwest National Laboratory, Richland, Wash., and mobility technology company Magna, based in Troy, Mich. The process is being developed specifically for the electric vehicle sector and the resulting lightweight aluminum could help extend driving range. The method reduces more than 50% of embodied energy and more than 90% of carbon dioxide emissions by eliminating the need to mine and refine the same amount of raw aluminum ore. The patented and award-winning Shear Assisted Processing and Extrusion (ShAPE) process collects scrap bits and leftover aluminum trimmings from automotive manufacturing and transforms it directly into suitable material for new vehicle parts. By reducing the cost of recycling aluminum, manufacturers may be able to reduce the overall cost of aluminum components, better enabling them to replace steel. For their experiments, the research team worked with an aluminum alloy known as 6063, or architectural aluminum. This alloy is used for a variety of automotive components, such as engine cradles, bumper assemblies, frame rails, and exterior trim. Researchers examined the extruded shapes using scanning electron microscopy and electron backscatter diffraction. Results showed that the ShAPE products are uniformly strong and lack manufacturing defects that could cause This microstructure within an aluminum trapezoid shows highly refined and uniform grain size, key to achieving a strong and reliable product. Courtesy of Nicole Overman and Cortland Johnson/PNNL. Ribbon cutting at funding announcement, April 11, IACMI Collaboration Facility in Knoxville, Tenn.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 7 REEs and separate impurities very efficiently. In addition, they found that supercritical carbon dioxide decreased the concentrations of impurities in the final REE product. Ultimately, their final products contained up to 6.47% REEs, compared with 0.0234% in the initial coal fly ash source. The new method eliminates the need to roast raw materials at extremely high temperatures, or greater than 500°C, and removes the need to extract the REEs with strong acids and a large quantity of toxic organic solvents, which also become a waste product in traditional extraction processes. wustl.edu. POTATO STARCH INSPIRES NEW PLASTIC MATERIAL Researchers from the University of Alicante in Spain developed a process for creating a water-soluble plastic material based on potato starch. According to the researchers, this new material is compostable and biodegradable and is suitable for use as a flexible film, in addition to having great advantages over existing materials. The researchers’ plastic is also highly stable and has a low migration rate. Team member Ignacio Martín Gullón explains the technology is intended for use in the packaging and single-use plastics industry as a direct replacement for conventional alternatives. The patented technology allows for a wide range of mechanical property manipulation, enabling manufacturers to tailor products to the needs of their clients. www.ua.es/en. Ignacio Martín Gullón (left) and Daniel Domene López with their potato starch at the University of Alicante. Courtesy of Asociacion RUVID.
8 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 of Cincinnati contributed to the international experiment using a strange metal made from an alloy of ytterbium, a rare earth metal. Physicists in the Hyogo lab then fired radioactive gamma rays at the strange metal to observe its bizarre electrical behavior. The experiment revealed unusual fluctuations in the strange metal’s electrical charge. Strange metals are of interest to a wide range of physicists studying everything from particle physics to quantum mechanics. One reason is because of their oddly high conductivity, at least under extremely cold temperatures, which gives them potential as superconductors for quantum computing. “The idea is that in a metal, you have a sea of electrons moving in the background on a lattice of ions,” Komijani TESTING | CHARACTERIZATION MICROSCOPE HELPS IMPROVE BATTERIES For the first time, scientists observed solid electrolyte interphase dynamics (SEI) in real time. Researchers developed a highly sensitive microscope to study the SEI layer and gain a better understanding of how batteries work. The operando reflection interference microscope (RIM) was created by a team of researchers from the University of Houston, in collaboration with the Pacific Northwest National Laboratory, Richland, Wash., and the U.S. Army Research Laboratory, Adelphi, Md. The researchers say their dynamic, noninvasive imaging tool has significant implications for developing next-gen batteries as it provides key insight into the rational design of interphases, a battery component that has been the least understood and most challenging barrier to developing electrolytes for future batteries. The research team applied the principle of interference reflection microscopy, where the light beam— centering at 600 nm with spectrum width of about 10 nm—was directed toward the electrodes and SEI layers and reflected. The collected optical intensity contains interference signals between different layers, carrying important information about the evolution process of SEI and allowing researchers to observe the entire reaction process. The researchers note that most current battery investigations use cryo-electron microscopes, which only take one picture at a certain time and cannot continuously track the changes at the same location. Their new imaging technique could also be applied to other state-ofthe-art energy storage systems. uh.edu. EXPLORING STRANGE METALS A collaborative team of physicists from the University of Cincinnati and Japan’s RIKEN and University of Hyogo are studying the unusual behavior of strange metals, which operate outside the normal rules of electricity. Theoretical physicist Yashar Komijani Triangular holes make this material more likely to crack from left to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. By warming a crystal of fresnoite, scientists at the DOE’s Oak Ridge National Laboratory, Tenn., discovered that phasons carry heat three times farther and faster than phonons, the excitations that usually carry heat through a material. The results could help improve the accuracy of heat transport simulations of energy materials. ornl.gov. Xiaonan Shan and Guangxia Feng work on the operando reflection interference microscope inside a “glove box” because the lithium-ion battery electrolyte is flammable. BRIEF Yashar Komijani worked with an international team of physicists to explore strange metals. Courtesy of Andrew Higley/U.C.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 9 explains. “But a marvelous thing happens with quantum mechanics. You can forget about the complications of the lattice of ions. Instead, they behave as if they are in a vacuum.” The researchers say it’s possible that one day strange metals could be just as ubiquitous in everyday technologies as conventional metals like copper. uc.edu, www.u-hyogo.ac.jp/english, www.riken.jp/en. HEAT TRANSFER: A CLOSER LOOK Researchers from the Jülich Research Centre in Germany are taking a closer look at heat transfer in granular materials, with a particular focus on the role roughness plays in the process. Granular materials contain large numbers of small, discrete particles, which collectively behave like uniform media. Their thermal conductivity is crucial to understanding their overall behavior—but so far, researchers haven’t considered how this value is affected by the surface roughness of their constituent particles. Scientist Bo Persson discovered that when this roughness is considered, thermal conductivity in granular materials is heavily influenced by particle sizes. These findings could help physicists to better describe a wide array of granular materials—from sand and snow, to piles of rice, coffee beans, and fertilizer. Persson and colleagues examined the thermal conductivity of granular materials in a humid atmosphere, where heat flows via air and water are especially relevant. Their discoveries will enable researchers of future studies to simulate the physical properties in granular materials more closely. www.fz-juelich.de/en. The cumulative probability for the heat conductance due to both the evanescent electromagnetic waves and heat conduction in water capillary bridges. Courtesy of The European Physical Journal B, 2023. Expand Your Heat Treating Knowledge with These Upcoming Courses Education asminternational.org/learning/courses/ Heat Treating Furnaces and Equipment June 15–16 ASM Headquarters & Virtual Classroom Vacuum Heat Treating September 7–8 ASM Headquarters & Virtual Classroom Basics of Heat Treating June 12–14 ASM Headquarters & Virtual Classroom HT, Microstructures, and Performance of Carbon and Alloy Steels August 21–22 Virtual Classroom
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 10 MACHINE LEARNING | AI ChatGPT SPEEDS MATERIALS RESEARCH Researchers at the University of Wisconsin-Madison are using OpenAI’s ChatGPT AI language model to quickly extract information from scientific literature. MS&E professor Dane Morgan has used machine learning for years in his lab to search for new types of materials with great success. Now, staff scientist Maciej Polak is brainstorming with Morgan about other tasks AI might help with. Polak knows that materials scientists often comb through long research papers to search for one small group of numbers to add to their datasets. “We thought we could just offload all of these time-consuming tasks onto an AI that could read those papers for us and give us that information,” says Polak. Asking chatbots, even ChatGPT, to look for and extract data from the full text of a paper remains beyond their capabilities. So Polak refined the technique, asking the bots to review sentence by sentence and decide whether each contained relevant data or not, a task that boiled papers down to one or two key sentences. He then asked the bots to put the information in a table, at which point a human could review it. The technique yielded an accuracy of 90%, allowing researchers to extract data from a set of papers to create a database on the critical cooling rates for metallic glasses. While the technique reduced the team’s paper-reading workload by about 99%, Polak wanted to refine it even more. So the scientists engaged in “prompt” engineering—figuring out questions that would cause the bot to double-check the information it pulled. They applied this approach to the extracted data table, and then asked the bot a series of follow-up questions to introduce the possibility that the dataset was wrong. That forced the AI to recheck the data and flag mistakes. In the vast majority of cases, the AI was able to identify faulty information. “Asking the program to extract data and then asking it to check if it is sure with normal sentences feels closer to how I train my children to get correct answers than how I usually train computers,” says Morgan. “It’s such a different way to ask a computer to do things.” He emphasizes that integrating AI into research does not replace graduate students and scientists. Instead, AI could allow researchers to pursue projects they haven’t had the time, money, or people to undertake. wisc.edu. USING AI FOR IMAGE ANALYSIS Researchers at the DOE’s Oak Ridge National Laboratory, Tenn., Graphic courtesy of text-to-image generator Stable Diffusion, using the prompt “researchers working with huge piles of data.” AI-generated image representing atoms and artificial neural networks. Courtesy of ORNL. developed a new software package inspired by machine learning to provide end-to-end image analysis of electron and scanning probe microscopy images. Called AtomAI, the software applies deep learning to microscopy data at atomic resolutions, thus providing quantifiable physical information including the precise position and type of each atom in a sample. Researchers can then quickly derive statistically meaningful information from immensely complex datasets. These datasets routinely include hundreds of images that each contain thousands of atoms and abnormalities in molecular structure. This improvement to data analysis allows researchers to engineer quantum atomically precise abnormalities in materials, and can be used to gain deeper insights into the materials’ physical and chemical qualities. AtomAI is also built to reduce errors in image processing by accounting for unintended changes in the image data, such as images of non-target materials, and by incorporating certain unchanging physical characteristics into the model. ornl.gov.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 1 1 PROCESS TECHNOLOGY NEXT-GEN SOLAR CELLS WITH LARGE PEROVSKITES A team of scientists from Penn State, State College, developed a new method to fabricate large perovskite devices that is more cost- and time- effective than was previously possible. The researchers say their technique could accelerate future materials discovery. “This method we developed allows us to easily create very large bulk samples within several minutes, rather than days or weeks using traditional methods,” says lead researcher Luyao Zheng. “And our materials are high quality—their properties can compete with single-crystal perovskites.” The team used a sintering method called the electrical and mechanical field-assisted sintering technique (EMFAST) to create the devices. Conventional processes for making perovskites involves wet chemistry—the materials and in the production of computer microchips. Because the process requires materials to be heated at thousands of degrees, organic polymers do not fare well. Scientists at the Cornell lab are studying how vapor-deposited polymers interact with bacterial pathogens and how bacteria, in turn, colonize polymeric coatings, from the paint used in ship hulls to the coating for biomedical devices. The researchers set out to develop a different approach to diversify CVD polymers by borrowing a concept from conventional solutions synthesis— the use of a so-called magic solvent, i.e., an inert vapor molecule, that isn’t incorporated into the final material, but instead interacts with a precursor in a way that produces new material properties at room temperature. The solvent in this case interacted with a common CVD monomer via hydrogen-bonding. This method can be applied to methacrylate and vinyl monomers for most anything with a polymer coating. cornell.edu. are liquefied in a solvent solution and then solidified into thin films. According to the scientists, these materials have excellent properties, but the approach is expensive, inefficient for creating large perovskites, and the solvents used may be toxic. Because it uses dry materials, the EM-FAST technique opens the door to include new dopants, ingredients added to tailor device properties, that are not compatible with the wet chemistry used to make thin films. The new process also allows for layered materials—one powder underneath another—to create designer compositions. In the future, manufacturers could design specific devices and then directly print them from dry powders. psu.edu. STRONGER THIN FILMS WITH MAGIC SOLVENT Researchers at Cornell University, Ithaca, N.Y., created a new all-dry polymerization technique that uses reactive vapors to create thin films with enhanced properties, such as mechanical strength, kinetics, and morphology. The synthesis process is gentler on the environment than traditional high-temperature or solution-based manufacturing and could lead to improved polymer coatings for microelectronics, advanced batteries, and therapeutics. Chemical vapor deposition (CVD) is a common process used to make defect-free inorganic nanolayer materials in semiconductor manufacturing BRIEF Alleima, Sweden, a manufacturer of advanced stainless steels and special alloys, opened a new hydraulic and instrumentation tubing factory on March 15 at its Mehsana Mill in Gujarat, India. Company officials say the factory will help meet a growing demand for locally manufactured products. alleima.com. Micrograph of an initiated chemical vapor deposition coating. Courtesy of Pengyu Chen/Cornell University. FAST-synthesized perovskite samples at various sizes. Courtesy of Penn State.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 12 SOFT ROBOTICS BREAKTHROUGH At Carnegie Mellon University, Pittsburgh, engineers are studying softbotics—a new generation of soft machines and robots manufactured by multifunctional materials that have integrated sensing, actuation, and intelligence. In a recent breakthrough, they developed a soft material with metal-like conductivity and self-healing properties that is the first to maintain enough electrical adhesion to support digital electronics and motors. The research team used the material, a liquid-metal filled organogel composite, in three applications: a damage- resistant snail-inspired robot, a modular circuit to power a toy car, and a reconfigurable bioelectrode to measure muscle activity on different locations of the body. The fully untethered snail robot used the self-healing conductive material on its soft exterior, which researchers embedded with a battery and electric motor to control motion. During the demonstration, the team severed the conductive material and watched as its speed dropped by more than 50%. Because of its self-healing properties, when the material was manually reconnected, the robot restored its electrical connection and recovered 68% of its original speed. The material can also act as a modular building block for reconfigurable circuits. Finally, the team demonstrated the material’s ability to be reconfigured to obtain electromyography (EMG) readings from different locations on the body. Because of its modular design, the organogel can be refitted to measure hand activity on the anterior muscles of the forearm and to the back of the leg to measure calf activity. This opens pathways to tissue-electronic interfaces like EMGs and EKGs using soft, reusable materials. The team says their work represents a breakthrough in the fields of robotics, electronics, and medicine. cmu.edu. PRINTABLE PEROVSKITE SOLAR CELLS The potential for perovskite solar cells to be manufactured at scale has been unlocked by scientists at Swansea University, U.K., who developed a lowcost and scalable carbon ink formulation while searching for an alternative to conventional evaporated gold electrodes. Using slot die coating in a roll-toroll (R2R) process, the researchers established a way to create fully print- EMERGING TECHNOLOGY A new study from the U.S. Geological Survey and Apple determined the rock-to-metal ratios for rare earth elements, describing how much ore and waste rock must be mined and processed to produce refined mineral commodities. This ratio is critical to understanding mine waste and potential environmental impacts. The report is published in the Journal of Cleaner Production, online at https://bit.ly/3L3TBjZ. BRIEF A close-up of a sample of the new fully roll-to-roll (R2R) coated device. Courtesy of Swansea University. Robotic snail powered by breakthrough self-healing, electrically conductive material. Courtesy of Carnegie Mellon University College of Engineering. able perovskite photovoltaics. The devices with carbon electrodes provided a similar photovoltaic performance to gold electrodes as part of a smallscale device on a rigid glass substrate, with power conversion efficiencies of 13%–14% and the additional benefits of outperforming at higher temperatures and having better long-term stability. The new fully R2R coated device, which was printed onto a 20-meter-long flexible substrate, produced a stabilized power conversion efficiency of 10.8%. “Perovskite solar cells show great promise in the drive toward cleaner, greener energy,” lead photovoltaic researcher Trystan Watson says. “The ability to produce a fully working device entirely in-line makes high- volume manufacturing easier and more economical and is a big step toward their commercialization. It unlocks the idea of a manufacturing process where a solar ink is added on one end and a solar cell emerges from the other.” www.swansea.ac.uk.
ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 13 SUSTAINABILITY BRIEF GREENER STEEL PRODUCTION A new adaptation for existing iron and steel furnaces could reduce CO emissions from the steelmaking industry by nearly 90%, adhering to standards set by the International Renewable Energy Agency that must be achieved by 2050 to limit global warming to 1.5°C. Developed by researchers at University of Birmingham, U.K., the radical reduction method operates through a closed loop carbon recycling system, which could replace 90% of the coke typically used in current blast furnace-basic oxygen furnace systems and produce oxygen as a biproduct. If implemented in the U.K. alone, the researchers say, it could save US$1.3 billion in production costs over five years while reducing overall U.K. emissions by 2.9%. Most of the world’s steel is produced via blast furnaces, which produce iron from iron ore, and basic oxygen furnaces, which turn that iron into steel. The novel recycling system captures the CO from the top gas and reduces it to carbon monoxide (CO) using a crystalline mineral lattice known as a perovskite material. The material was chosen as the reactions take place within a range of temperatures (700°- 800°C) that can be powered by renewable energy sources or otherwise generated using heat exchangers connected to the blast furnaces. Under a high concentration of CO , the perovskite splits CO into oxygen, which is absorbed into the lattice, and CO, which is fed back into the blast furnace. The perovskite can be regenerated to its original form in a chemical reaction that takes place in a low oxygen environment. The oxygen produced can be used in the basic oxygen furnace to produce steel. The researchers filed a patent application covering the system and its use in metal production and are looking for long-term partners to participate in pilot studies, deliver this technology to existing infrastructure, or collaborate on further research to develop the system. www.birmingham.ac.uk. GAS AND LIQUIDPROOF MATERIAL Using liquid metal, an international team of researchers led by scientists at North Carolina State University, Raleigh, created a technique to produce an elastic material that is impervious to both gases and liquids. Applications for the material include use as packaging for high-value technologies that require protection from gases, such as flexible batteries. The new method makes use of a eutectic alloy of gallium and indium (EGaIn), which is liquid at room temperature. After forming the alloy into a thin film, the researchers encased it in an elastic polymer. Then, they studded the interior surface of the polymer with microscale glass beads, which prevented the liquid film of EGaIn from pooling. The resulting elastic material is essentially a pliable bag or sheath lined with liquid metal, which does not allow gases or liquids in or out. The researchers tested the effectiveness of the new material by assessing the extent to which it allowed liquid contents to evaporate, as well as the extent to which it allowed oxygen to leak out of a sealed container made of the material. Additional studies are in progress. ncsu.edu. Henkel Adhesive Technologies and cyclos-HTP Institute (CHI), both in Germany, announced a partnership to bring together adhesives and coatings expertise with downstream recycling knowledge. The goal is to give industrial customers better access to in-house testing and certification, materials science R&D, and sustainable packaging design consultation. CHI is one of Europe’s leading institutes for recyclability testing and certification. henkel.com. A new method for reducing CO2 emissions in steelmaking is underway. Courtesy of Scanrail. Researchers developed a new material that is elastic, flexible, and impervious to both gases and liquids. Courtesy of Michael Dickey.
14 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 ADVANCING DIFFUSION BONDED COMPACT HEAT EXCHANGERS FOR HIGH TEMPERATURE APPLICATIONS Mohamed Elbakhshwan, Lukas Desorcy, Ian Jentz, and Mark Anderson, University of Wisconsin–Madison Fei Gao and Todd Allen,* University of Michigan, Ann Arbor Mark Messner, Argonne National Laboratory, Lemont, Illinois Mike McMurtrey, Idaho National Laboratory, Idaho Falls Jim Stubbins, University of Illinois Urbana-Champaign John Shingledecker, FASM,* Electric Power Research Institute (EPRI), Charlotte, North Carolina Billy Nollet, Fort Lewis College, Durango, Colorado Bob Keating and Suzanne McKillup, MPR Associates Inc. Enhancement of the di usion bonding process for the development of compact heat exchangers provides an energy e cient solution for hightemperature applications in advanced nuclear reactors and other technologies. *Member of ASM International Image courtesy of Vacuum Process Engineering Inc. HEAT EXCHANGERS
15 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 Fig. 1 — (a) Schematic shows the stacking of pre-etched plates that form a homogeneous diffusion bonded block after applying high temperature and pressure. (b) Optical image shows the cross section of CHX with 1.6 channel diameter. (c) Actual stainless steel 316L diffusion bonded CHXs, and (d) Schematic shows the size difference between CHX and a stack of three shell and tube exchangers with the same thermal duty, at the same pressure drop. An ongoing effort to advance various energy systems (nuclear, solar, geothermal, and fossil) is underway around the world to meet the increasing demand for clean, affordable, and resilient energy, while enhancing the safety and efficiency resource use. These systems could benefit from advanced compact heat exchangers (CHXs) with unique designs and configurations that optimize heat transfer at reduced cost. Advancements in manufacturing processes and new innovative developments and designs have resulted in significant improvements in heat exchanger technology. CHXs are characterized by low space and weight requirements, high thermal effectiveness, low-pressure drop, moderate to high design pressure capability, and high effectiveness approaching 95%, as shown in Fig. 1. This combi- nation of attributes is desirable to improve cost and efficiency of advanced nuclear reactor technologies now under development. Solid state diffusion bonding has been used to create CHXs for various applications. It is a solid-state welding process in which two contacting surfaces bond under high temperature and pressure in a vacuum environment. The bonding process is performed at elevated temperature, around 80% of the melting point of the bonded materials. The high temperature allows atomic diffusion across the bonding line, making a permanent bond between similar or dissimilar materials with no residual strain or deformation in the bonded parts. During the manufacturing of diffusion bonded CHXs, small channels (on the order of a mm in size) are chemically etched or machined into thin metallic sheets and these sheets are stacked and diffusion bonded into a solid block resulting in a high surface area to volume ratio in comparison to other traditional heat exchangers technologies. In general, diffusion bonding has been a successful manufacturing process for low to intermediate temperature CHXs made of various stainless-steel alloys such as 316L and 304, as well as other copper and titanium alloys. However, there is limited information about the diffusion bonding (and manufacturing) of CHXs in high temperature applications and associated selection of bonded materials, bonding conditions, mechanical perfor- mance, and thermo-fluid characteristics. This article aims to shed light on the available knowledge and the ongoing research being conducted to address gaps in information and application. AVAILABLE KNOWLEDGE Substantive knowledge exists in the literature for the successful diffusion bonding of stainless steel 316 and 316L, achieving properties equivalent to that of the wrought metal at both room and elevated temperatures[1,4]. However, those alloys are limited for high-temperature applications. Of particular interest for the nuclear industry, there are a total of six alloys qualified in Section III, Division V of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) for elevated-temperature nuclear construction: Nickel- based Alloy 617, 316H stainless steel (SS316H), 304H (SS304H), and Alloy 800H; and ferritic/martensite steels grade 22 (2.25Cr-1Mo) and 91 (9Cr-1Mo-V). There have been multiple endeavors to diffusion bond Alloy 617 and only a subset of these efforts characterized the elevated- temperature mechanical properties. Precipitate formation at the interfaces is frequently cited as impeding grain growth, therefore preventing successful diffusion bonding. In general, the elevated-temperature time dependent and cyclic properties, particularly creep- fatigue of the diffusion bonded Alloy 617, were significantly reduced compared to the as-received base metal, with failure in the diffusion-bonded specimens occurring at the weakest interface[5-8]. Recent studies focused on various methods to enhance the joints mechanical properties using post-bonding heat treatment and pre-bonding oxidation followed by removal of surface oxides[5-7]. Diffusion bonding of Alloy 800H suffered the same issues as Alloy 617, but the use of an Ni interlayer was found to enhance the bonding process and achieve reasonable strength and ductility[9-11]. On the other hand, diffusion bonding of 316H stainless steel did not lead to significant reduction in strength and/or ductility. The diffusion bonding lines were found to contain carbide particles which compromise the mechanical properties, but post-bonding heat treatment was found to completely dissolve them. Although the aforementioned studies showed the limitations of the current technology and potential for improved high-temperature per- (a) (b) (c) (d)
16 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 formance of the diffusion bonded joints, there still exists a lack of fundamental knowledge and data for both the diffusion bonding process and the resultant high-temperature time dependent bond properties including: 1. The role of precipitates and oxide particles. 2. The control of pre-bond sheet surface quality. 3. The importance of base alloy composition and minor alloying elements. 4. The elevated-temperature testing methods, performance, and the need for more robust acceptance criteria. 5. The failure mechanism of the bonded joints. CURRENT RESEARCH DIRECTIONS To address those knowledge gaps, a new multi-institution project supported by the U.S. Department of Energy, Office of Nuclear Energy (DOE-NE) and led by University of Michigan Ann Arbor, aims to (1) improve diffusion bonding of alloys of interest for elevated-temperature nuclear service (Alloy 617 and type 316H stainless steel) so that the elevated-temperature mechanical performance is superior or equivalent to the wrought product form, and (2) establish and verify acceptance criteria to ensure with reasonable confidence that the diffusion-bonded material will behave as intended for the entirety of its service life. This is critical for code case qualification of diffusion bonding for Section III, Division 5 applications. The overall project structure is depicted in Fig. 2, which combines computational modeling, lab scale bonding trials, detailed material characterizations and mechanical testing in successive iterations to expand knowledge more rapidly from the labscale to commercial processing with an aim to provide new guidance for acceptance of diffusion bonding compact heat exchangers for high-temperature application. First, optimal bonding parameters will be determined in successive bonding campaigns with significant input from developed phase field and crystal plasticity models. For each alloy of interest, bond optimization may be separated into two separate cycles: both rapid iteration and acceptance qualification. This approach speeds up the optimization process and reduces material use. The rapid iteration cycle aims to quickly establish diffusion bonding parameters that yield the best microstructure at the bond interface. This may be achieved by employing a high-throughput approach to optimize the diffusion bonding parameters using small samples to reduce costs and resources. The best microstructure is that which is indistinguishable from the rest of the bulk microstructure, i.e., bearing no gross defects, minimal precipitation, and extensive grain boundary migration at the interface. Examples of bond-line characterization by electron backscatter diffraction (EBSD) analysis for two samples are shown in Fig. 3. After a good microstructure is obtained and verified, mechanical screening may be conducted on the small samples to further verify bond Fig. 2 — Illustrative sketch of the action plan for the development of di usion bonding for high-temperature applications.
1 7 ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 optimization prior to moving forward with larger footprint bonding trials. The microstructure at these interfaces will inform phase field models to develop a multi-scale metallurgical model of the diffusion bonding process that emulates grain recrystallization and growth at the bond interface and investigates the impact of material and preparation parameters on the bond. In addition, it allows the development of material deformation crystal plasticity models that predict the creep strength of the bond based on microstructure and predict the creep, fatigue, and creepfatigue performance for long-term service conditions that cannot be achieved in a reasonable experimental time. Second, the acceptance qualification loop would involve fabrication of diffusion-bonded specimens in compliance with the size requirements specified in Section IX of the ASME BPVC. These are plates that are 200 by 200 mm with at least 50 diffusion bonds. Bonding parameters identified in the rapid iteration loop will be applied in a commercial vacuum hot press. Detailed microstructural characterization and mechanical testing will be performed on bond coupons and test specimens cut out of these larger test blocks. Bond strength would be determined through tensile, creep, fatigue, and creep-fatigue testing and complemented with models based on the microstructure that can predict long term performance. Results will be compared to starting sheet performance after thermal exposure to the optimized diffusion bonding cycle to provide direct correlation of properties in addition to comparisons with the larger existing wrought material databases used in heat exchanger design. Figure 4 shows an example of macro-scale characterization of a diffusion bonded block after creep testing to confirm failure location and strain accumulation. The goal is to use the results from the pre- and post-test microstructural characterization, mechanical testing, and multiple length scale computational models to develop acceptance criteria to ensure that the diffusion-bonded plate will perform as intended during Section III, Division 5 service. These acceptance criteria will likely focus on a performance-based approach rather than a fabrication-based approach. The proposed acceptance criteria may be a list of microstructural and mechanical property requirements that must be met. Furthermore, the models may be utilized to help identify boundary conditions and sensitivity of these of fabrication methodology for the acceptance criteria. As a final step after the acceptance criteria have been developed, bonded blocks will be fabricated with and/or without channels that meet the size requirements specified in Section IX of the ASME BPVC. Detailed microstructural characterization and mechanical testing will be performed on bond coupons and test specimens cut out of these larger test blocks. Results will be used to validate the acceptance criteria for ASME BPVC Section III, Division 5 applications. This will utilize the results from microstructural and mechanical property characterization as well as phase field and crystalplasticity modeling for the plates with and without micro-channels. SUMMARY Diffusion bonded heat exchangers represent an enabling technology for the energy transformation with great potential for high-temperature applications in advanced nuclear reactors and other technologies. However, the current research reveals a number of Fig. 3 — EBSD maps of grain size distribution around the di usion bonding line of Alloy 800H; (le ) shows grain interdi usion across the bonding line and (right) shows oxide particle trapped at the bonding line. Fig. 4 — Example of post-test analysis of a stainless steel 316 di usion bonded subject to creep testing at 750°C showing creep cavity formation (insert) and failure along the bond line. Additional measurements (mm) indicate substantial deformation (creep strain accumulation) between bond lines prior to failure and outer diameter crack initiation at bond lines (arrows).www.asminternational.org