21 23 32 P. 12 JANUARY/FEBRUARY 2023 | VOL 181 | NO 1 ASM Welcomes New President Advanced Manufacturing Landscape Phase Analysis Technique Selection SUSTAINABLE AM FOR MILITARY APPLICATIONS EMERGING TECHNOLOGIES
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21 23 32 P. 12 JANUARY/FEBRUARY 2023 | VOL 181 | NO 1 ASM Welcomes New President Advanced Manufacturing Landscape Phase Analysis Technique Selection SUSTAINABLE AM FOR MILITARY APPLICATIONS EMERGING TECHNOLOGIES
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39 ASM NEWS The latest news about ASM members, chapters, events, awards, conferences, affiliates, and other Society activities. POINT-OF-NEED INNOVATIONS: METAL ADDITIVE MANUFACTURING AND REPAIR Paul G. Allison, J. Brian Jordon, M. Brady Williams, Troy Pierson, Ryan Kinser, Timothy W. Rushing, Brandon J. Phillips, and Kevin J. Doherty Additive friction stir deposition uses secondary feedstocks such as machine chips and damaged components to make in-field repairs at the point of need. 12 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 2 A U.S. Marine conducts preflight checks on an MV-22 Osprey before a transpacific flight. Courtesy of Cpl. Cameron Hermanet. On the Cover: 50 STRESS RELIEF From the lighter side of engineering— the rheology of Oreo cookies, recycling wind turbines, and studying sea slugs for AI algorithms. 38 AEROMAT PROGRAM HIGHLIGHTS AeroMat brings together hundreds of aerospace professionals and exhibiting companies to discuss and display the latest advancements in sustainable aerospace materials and processes.
4 Editorial 5 Feedback 5 Research Tracks 10 Machine Learning 6 Metals/Polymers/Ceramics 8 Testing/Characterization 11 Emerging Technology 50 Stress Relief 51 Editorial Preview 51 Special Advertising Section 51 Advertisers Index 52 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. 1, JANUARY/FEBRUARY 2023. Copyright © 2023 by ASM International®. All rights reserved. Distributed at no charge to ASMmembers 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. 21 DAVID B. WILLIAMS 2022-2023 PRESIDENT OF ASM INTERNATIONAL Meet David B. Williams, FASM, the new president of ASM, and learn about his academic and scientific background, leadership, and contributions as a researcher and educator. 23 ADVANCED MANUFACTURING: NAVIGATING THE PATH FORWARD William E. Frazier, Jack Beuth, Glenn S. Daehn, David U. Furrer, Michael Maher, and Scott D. Henry Highlights from a member survey and panel discussion outlining the challenges and benefits of advanced manufacturing for the materials community. 32 PHASE ANALYSIS PRIMER: HOW TO SELECT THE RIGHT ANALYTICAL TECHNIQUE Rajan Bhambroo Knowing the advantages and disadvantages of various analysis methods can help determine the best approach for the task at hand. FEATURES JANUARY/FEBRUARY 2023 | VOL 181 | NO 1 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 3 21 36 32 23 36 TECHNICAL SPOTLIGHT SUSTAINABLE ALLOY SOLUTION FOR ENGINE VALVETRAIN APPLICATIONS J513 alloy offers lower costs and higher performance for diesel and natural gas engine applications while also requiring substantially less cobalt usage.
4 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 ASM International 9639 Kinsman Road, Materials Park, OH 44073 Tel: 440.338.5151 • Fax: 440.338.4634 Joanne Miller, Editor joanne.miller@asminternational.org Victoria Burt, Managing Editor vicki.burt@asminternational.org Frances Richards and Corinne Richards Contributing Editors Anne Vidmar, Layout and Design Allison Freeman, Production Manager allie.freeman@asminternational.org Press Release Editor magazines@asminternational.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 ASMBOARDOF 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 BOARDMEMBERS 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 fromarticles 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. LABS SPARK BREAKTHROUGHS Graphic of lasers igniting nuclear fusion in a pellet of fuel. Courtesy of LLNL. To commemorate its 100 years of publication in 2022, Science News curated a list of the most important stories from each decade. Among the 1940s was the 1945 Smyth Report, which chronicled atomic energy history, specifically the contributions of the Manhattan Project. Written by a physicist, the report drew some criticism for skimming over the importance of chemistry to the success of the project. Now, a recently published book, “Wilhelm’s Way,” tells how Harley Wilhelm, a chemistry professor at Iowa State College, was a key contributor to the Manhattan Project. Wilhelm and his team developed a process for purifying uranium, which was needed for the controlled nuclear chain reaction of the atomic bomb. When World War II ended, he became a co-founder of the Ames National Laboratory at Iowa State. Wilhelm later served as an ASM trustee, 1956-1957. The national labs began opening during and after the war to aid the significant scientific research needed during that era. Today, the Department of Energy oversees 17 national labs across the country. Their peacetime research has expanded to cover everything from sustainable energy to artificial intelligence. Like Wilhelm before, today numerous ASM members are making unique contributions on the staffs of these important research centers. I reached out to a fewof thosemembers for their insights. Mary O’Brien spoke to me about the vital way the labs contribute to our world. “As the daughter of a former West Point graduate and Army ranger, I could not be prouder to continue my family’s legacy of contributing to national and global security throughmy work as a scientist at Los Alamos National Laboratory. The importance of the work we do cannot be understated. Not only do we push the boundaries of what humanity knows scientifically, the work we do also plays a crucial global role in deterring nuclear attacks and preventing large scale conventional warfare.” The labs continue delivering on these essential missions every day. Science News joined other journalists around the world in reporting on the nuclear fusion breakthrough announcement of December 5, 2022, by Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF). The game changing, net-positive experiment provides a promise of a clean energy source, albeit still in the distant future. For a comment on the momentousness of this fusion development, I turned to Ellen Cerreta, FASM, who is highlighted in our Members in the News section for recently being named associate lab director for physical sciences at Los Alamos National Laboratory. Cerreta shared, “Lawrence Livermore’s recent achievement of ignition at NIF is remarkable not only because of its significant impact for the science of stockpile stewardship but because it marks the success of nearly half a century of worldwide research that has been performed to understand and achieve fusion ignition.” LLNL and all the national labs have been advancing science across so many technology sectors for decades and will continue to be in the forefront of many future discoveries. They are sure to be on Science News’ 200th anniversary list. joanne.miller@asminternational.org
A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 5 CHIPS CHARGE FORWARD The most recent editorial column (“Mapping Out Solutions,” AM&P Nov/ Dec 2022) brought back memories of working at IBM in Hopewell Junction, N.Y., in the summer of 1967 before grad school. I believe the IBM 360 computer was the first to use a chip as a transistor or diode. At the time, vacuum tubes cost a few dollars, a solid state transistor was about a buck, and the chip was a penny. The process included soldering 0.005-in. diameter balls onto each chip. The metallurgy was complicated and they were having quality problems. I figured out how to fix the process. When I handed in my report, they said thanks. I asked if they were going to change the process and they said no. I asked why. They said I did a great piece of work, but it takes a month to implement a change and the next month they were going to a whole new technology. It was obvious they had given me a “make work” job to see if they wanted FEEDBACK / RESEARCH TRACKS We welcome all comments and suggestions. Send letters to joanne.miller@asminternational.org. Electronics have progressed from the vacuum tube, to the transistor, to the tiny dot of a solid logic technology “chip” transistor. Courtesy of IBM. engineering, technology, science, and business colleges. Hanchen Huang, FASM My team and I recently won an entrepreneurship grant at the University of Virginia to develop a machine learning platform targeted to materials research. We are working hard to complete the development phase and hopefully share it with fellow ASM members to collect feedback. Ho Lun Chan STIMULI-CONTROLLED METAMATERIALS A multidisciplinary research team from the University at Buffalo, the DEVCOM Army Research Laboratory, and the University of Maryland at College Park reports the controlled chemical energy release from spatially programmed molecular energetic ferroelectric crystals. “By using self-assembly directed additive manufacturing, we are able to control the mesoscale structure of a molecular energetic compound, together with the polarization-controlled heat transfer due to its ferroelectric nature, leading to the control of chemical energy release during the bond breaking,” explains Prof. Shenqiang Ren at the University at Buffalo. According to the team of scientists, such stimuli-controlled to hire me later. I was happy to learn about chips and have been amazed at the advances since then, both in chips and the analysis tools such as 3D atom probe tomography. Bill Hamm, FASM A+ ENTREPRENEURSHIP I was delighted to contribute to the recent discussion of entrepreneurship in AM&P (Nov/Dec 2022). This topic is critically important and deserves more attention at research universities, particularly within their metamaterials could provide a path toward the controlled release of chemical energy and its conversion to electric or thermal energy. Potential applications include use in energy conversion systems, energetic materials, and thermal conductors, among others. buffalo.edu. FEEDBACK
A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 6 METALS | POLYMERS | CERAMICS Messe Düsseldorf extends its metal trade fair portfolio with a Cairo investment deal. As a special area of Metal & Steel Egypt, September 2-4, 2023, the four trade fairs GIFA Middle East Africa, METEC Middle East Africa, wire Middle East Africa, and Tube Middle East Africa will be held at the Egypt International Exhibition Center for the first time. www.metec.de. Thyssenkrupp Steel Europe and thyssenkrupp Hohenlimburg signed letters of intent with the Bilstein Group, Germany, for the supply of climate-friendly bluemint steel from 2023 on. From 2026 forward, steel will come from thyssenkrupp Steel’s direct reduction plants with melters in Duisburg, to be operated with green hydrogen and renewable electricity. Bilstein makes products for cold rolling applications in the automotive and toolmaking industries. thyssenkrupp.com. BRIEFS EASY-TO-SYNTHESIZE, SELF-HEALING GELS A research team consisting of Japan’s National Institute for Materials Science, Hokkaido University, and Yamaguchi University created a new method for easily synthesizing a self-healing polymer gel made of ultrahigh molecular weight (UHMW) polymers and nonvolatile ionic liquids. The recyclable and self-healable polymer gel could potentially be used as a durable, ionically conductive material for flexible Internet of Things devices. Most reported self-healing polymeric materials in recent years have been based on a chemical approach in which functional groups capable of reversible dissociation and reformation were integrated into polymeric networks. However, this method often requires precise synthetic techniques and complexmanufacturing processes. On the other hand, an STABILIZING STRATEGY FOR HIGH-ENTROPY ALLOYS Scientists at City University of Hong Kong discovered that tailoring the concentration of cobalt in high entropy alloys can prevent nanoparticles from rapid coarsening at high temperatures. This stabilizing strategy paves the way for designing novel, thermally stable, and chemically complex alloys in various engineering fields. Nanoparticle-strengthening technology is regarded as a powerful strategy to create materials with unique structural and functional properties. It’s been widely applied to innovate highstrength materials, like advanced aluminum alloys, steels, and superalloys. The researchers found that cobalt can effectively trigger a sluggish lattice diffusion effect in the nickel-cobalt-iron-chromium-aluminum-titanium (NiCoFeCrAlTi) alloy system by decreasing the interdiffusion coefficient of other elements. The cobalt also was shown to reduce the average particle size and further improve the thermal stability of these nanoparticles. According to lead scientist Yang Tao, the team’s findings create a highly effective pathway for well-targeted design of high-performance alloys with excellent thermal and mechanical properties for high-temperature structural applications. www.cityu.edu.hk. SEMmicrographs of nanoparticles in the chemically complex alloys aged at 1000°C for 240h, with their average diameters displayed in the bars. Courtesy of B. Xiao, et al., Nature Communications (2022). DOI: 10.1038/s41467-022-32620-6. Schematic depicting UHMW gels’ ability to be self-heal along with photos of the recombined gels being stretched. Courtesy of Ryota Tamate/National Institute for Materials Science.
A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 7 alternative physical approach—as in the use of physical entanglement of polymer chains, for example—to synthesizing versatile polymeric materials with self-healing capabilities has, until now, rarely been explored. The team created their new technique for easily synthesizing UHMW gels composed of entangled UHMW polymers using ionic liquids. The mechanical properties of UHMW gels were found to be superior to those of conventional, chemically crosslinked gels. In addition, they can be recycled via thermal processing and exhibit high self-healing capabilities at room temperature. www.nims.go.jp/ eng, www.global.hokudai.ac.jp, www. yamaguchi-u.ac.jp/english. DEEP SEA VACUUM COLLECTS METALS A collaboration between a conglomerate of European countries called Blue Harvesting has created and tested a new collector that can gather valuable metals such as copper, manganese, nickel, and cobalt from the deep sea bottom with minimal disturbance to the natural environment. The scientists say their collector could be thought of as a deep sea vacuum cleaner, driven by water pressure and powered entirely by electricity. The team tested their mining vehicle, Apollo 2, in the Mediterranean Sea at a depth of around 300 m, where the conditions are very similar to the deep sea. They equipped the collector with various sensors that measured how much sediment was disturbed during the mining operation as the nodules were gathered from the sea floor. “We carried out all the tests we had planned to do,” report the scientists, “which is not always feasible when working with a prototype and being dependent on sea and weather conditions, and Apollo 2 proved extremely efficient at picking up the nodules without causing large dust clouds of sediment. In fact, these ‘plumes’ seemed to be smaller than usual and contained significantly less sediment than expected.” www.blueharvesting-project.eu. This unique underwater vacuum cleaner can harvest metals necessary for next-generation energy sources . Courtesy of Del University of Technology. One Part Supreme 10HT for STRUCTURAL TOUGHENED EPOXY BONDING Hackensack, NJ 07601 USA • +1.201.343.8983 • main masterbond.com www.masterbond.com HIGH BOND STRENGTH Lap shear strength | 3,600-3,800 psi Tensile modulus | 450,000-500,000 psi NASA LOW OUTGASSING Per ASTM E595 standards SERVICE TEMPERATURE RANGE From 4K to +400°F Back by popular demand! The ASM Thermal Spray Society will again provide students and emerging professionals an opportunity to interact with the world’s best, brightest, and most influential leaders in the global thermal spray industry. Each session kicks off with a presentation, followed by an engaging and lively Q&A moderated by Dr. Rogerio Lima. Join us each month to hear directly from the experts! REGISTER TODAY! asminternational.org/web/tss-open-mic-series
8 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 According to the researchers, they expected MAPbI3 to behave like an insulator when they exposed it to terahertz light. What they found, however, was that there was a lot of variation in light scattering along the boundary between the grains. This wide variation sheds light on the material’s degradation problem, and the findings could be useful for improving and manipulating it in the future. “We believe that the present study demonstrates a powerful microscopy tool to visualize, understand, and potentially mitigate grain boundary degradation, defect traps, and materials degradation,” says Wang. “A better understanding of these issues may enable developing highly efficient perovskite-based photovoltaic devices for many years to come.” ameslab.gov. TESTING | CHARACTERIZATION LAW OF FRICTION DISCOVERY A new method to measure the interfacial shear between two atomic layers was established by researchers at New York University’s Tandon School of Engineering. The findings also uncovered that the measured quantity is inversely related to friction, following a new law. The researchers say their work could lead to more efficient manufacturing processes, greener vehicles, and an overall more sustainable world. Studying bulk graphite and epitaxial graphene films grown with different stacking orders and twisting, researchers measured the hard-to-access interfacial transverse shear modulus of an atomic layer on a substrate. Results revealed that the modulus is largely controlled by the stacking order and the atomic layer-substrate interaction and demonstrated its importance in controlling and predicting sliding friction in supported 2D materials. The experiments showed a general reciprocal relationship between friction force per unit contact area and interfacial shear modulus for all the graphite structures the scientists investigated. “The interaction between a single atomic layer of a material and its substrate governs its electronic, mechanical, and chemical properties,” explains lead researcher Elisa Riedo. “Gaining insight into that topic is important, on both fundamental and technological levels, in finding ways to reduce the energy loss caused by friction. Our results can be generalized to other 2D materials as well,” Riedo continues. “This presents a way to control atomic sliding friction and other interfacial phenomena, and has potential applications in miniaturized moving devices, the transportation industry, and other realms.” engineering.nyu.edu. NEW MICROSCOPE EXAMINES SOLAR CELL MATERIAL A new characterization tool developed by researchers at the DOE’s Ames National Lab in Iowa is helping scientists gain insight into a possible alternative material for solar cells. The research team, led by senior scientist Jigang Wang, developed a microscope that uses terahertz waves to collect data on material samples. The team then used their microscope to explore methylammonium lead iodide (MAPbI3) perovskite, a material that could potentially replace silicon in solar cells. The main challenge to using MAPbI3 for this application is that it degrades easily when exposed to elements like heat and moisture. Triangular holes make this material more likely to crack from left to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. 9T Labs AG, Zurich, is collaborating with Purdue University, West Lafayette, Ind., to research and test the potential to build structural aerospace composite applications at scale with 9T’s additive fusion technology. Purdue’s Composite Manufacturing and Simulation Center will provide the tools and resources to analyze, simulate, and test composite performance. 9tlabs.com. BRIEF In this artistic rendering of how atomic shear is measured, a nanoscale tip pulls atoms so they slide on top of others. Courtesy of Martin Rejhon. In this visualization of a microscope tip exposing material to terahertz light, the colors on the material represent the lightscattering data, while the red and blue lines represent terahertz waves.
A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 9 MICROPLASTICS IN COOKWARE International collaborators from Newcastle University, U.K., and Flinders University, Australia, conducted a study to measure how millions of tiny plastic particles potentially come off during cooking and in the wash as nonstick pots and pans gradually lose their coating. Researchers report that one surface crack on a Teflon-coated pan can release about 9100 plastic particles. And at a microscale, using Raman spectroscopy and an algorithm model, scientists identified the release of 2.3 million microplastics and nanoplastics from broken coating. “The nonstick coating material Teflon is generally a family member of PFAS,” explains Newcastle researcher Cheng Fang. “Given the fact PFAS is a big concern, these Teflonmicroparticles in our food might be a health concern, [which] needs investigating because we don’t know much about these emerging contaminants.” The study developed a molecular spectrum approach to directly visualize and identify the Teflon microplastics and nanoplastics, which are more difficult to monitor than other plastics. Researchers say their work highlights the need to gain insights into the threat of Teflon plastic debris during daily cooking. “It gives us a strong warning that we must be careful about selecting and using cooking utensils to avoid food contamination,” the researchers continue. “More research is recommended to address the risk assessment of the Teflon microplastics and nanoplastics.” www.ncl. ac.uk, www.flinders.edu.au. SEM and Raman imaging of Teflon pans reveal the millions of microplastics and nanoplastics that might be released during cooking. DOI: 10.1016/j.scitotenv.2022.158293. ASM HANDBOOK VOLUMES 2A & 2B ALUMINUM SET asminternational.org PURCHASE THIS TWO-VOLUME SET AT A SPECIAL DISCOUNTED PRICE! The set includes ASM Handbooks, Volume 2A: Aluminum Science and Technology and Volume 2B: Properties and Selection of Aluminum Alloys.
A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 1 0 MACHINE LEARNING | AI AI AIDS MOLTEN SALTS RESEARCH In a new study, researchers at the DOE’s Argonne National Laboratory showed how artificial intelligence could help pinpoint the right types of molten salts, which can serve as both a coolant and fuel in nuclear power reactors that generate electricity without emitting greenhouse gases. They can also store large amounts of energy, which is increasingly needed on an electric grid with fluctuating sources such as wind and solar power. Scientists are exploring different combinations of salts to get the exact properties needed to cool and fuel a nuclear power reactor efficiently for decades. These properties include lower melting temperatures, the right consistency, and the ability to absorb high amounts of heat, among others. The potential variations are nearly endless. The study set out to determine whether computer simulations driven by machine learning could guide and refine real-world experiments at Argonne’s Advanced Photon Source (APS). Researchers used the powerful x-rays at the APS to better understand specific salt mixtures by looking closely at their structures. But the time and cost associated with real-world experiments makes it desirable to narrow the field of candidates that undergo inspection. Building on previous modeling that explored heat-resistant materials, researchers used active learning to create a transferable model to analyze molten salts. Rather than being fitted for one or two specific molten salt mixture compositions, the transferable model canbe applied tomixtures across the composition space. The model makes predictions based on principles rather than a set of predefined answers. Now that the researchers have shown this approach can work, the next step is to work with even more complex data. anl.gov. ADVANCED MATERIALS DESIGN WITH AI Microscopic materials analysis is essential to achieving desirable performance in next-generation nanoelectronic devices. However, the magnetic materials involved in such devices often exhibit incredibly complex inter- actions between nanostructures and magnetic domains, which makes functional design challenging. To address this, a team of researchers from Tokyo University of Science succeeded in automating the interpretation of microscopic image data. This was achieved using an “extended Landau free energy model” that the team developed using a combination of topology, data science, and free energy. The model could illustrate the physical mechanism as well as the critical location of the magnetic effect, anditproposedan optimal structure for a nano device. The model used physics- based features to draw energy land- scapes in the information space, which could be applied to understand the complex interactions at the nanoscale in a wide variety of materials. The team’s results indicate that the demagnetization energy near a defect gives rise to a magnetic effect, which is responsible for the “pinning phenomenon.” Further, the scientists could visualize the spatial concentration of energy barriers, a feat that had not been achieved until now. Finally, the team proposed a topologically inverse design of recording devices and nanostructures with low power consumption. The model proposed in this study is expected to contribute to a wide range of applications in the development of spintronic devices, quantum information technology, and Web 3. www.tus.ac.jp/en. Researchers are searching for the ideal characteristics of molten salt, which can serve as both a coolant and fuel in advanced nuclear reactors. An image depicting the extended Landau free energy model developed by a research team from Tokyo University of Science.
A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 1 1 SOFT ROBOT SELF-HEALS Combining optical sensors with a composite material, a research team from Cornell University, Ithaca, N.Y., created a soft robot that can detect when and where it is damaged and respond by healing itself. For years, Cornell’s Organic Robotics Lab has used stretchable fiberoptic sensors to make soft robots and related components— from skin to wearable technology—as nimble and practical as possible. One of the key virtues of fiberoptic technology is that waveguides are still able to propagate light if they are punctured or cut. The researchers combined optical sensors with a polyurethane urea elastomer that incorporated hydrogen bonds for rapid healing and disulfide exchanges for strength. The resulting self-healing light guides for dynamic sensing, or SHeaLDS, provide reliable dynamic sensing, are damage-resistant, and can self-heal from cuts at room temperature without any external intervention. To demonstrate the technology, the team installed SHeaLDS in a soft robot resembling a four-legged starfish, equipped with feedback control. After the researchers punctured one of its legs a total of six times, the robot was able to detect the damage and self-heal each cut in about a minute. The robot could also autonomously adapt its gait based on the damage it sensed. While the material is sturdy, it is not indestructible. Next, the team plans to integrate the SHeaLDS with machine learning algorithms that recognize tactile events to eventually create “a very enduring robot that has a self-healing skin, but uses the same skin to feel its environment to be able to do more tasks.” cornell.edu. CURVED NANOELECTRONICS An international research team involving collaborators from Italy, Germany, the U.K., and China report that exciting developments induced by curvature at the nanoscale allow them to define a completely new field—curved nanoelectronics. From microelectronic devices with enhanced functionality to large-scale nanomembranes consisting of networks of electronic sensors that can provide improved performance, the scientists examined significant development directions in the field of electronic materials with curved geometries at the nanoscale. According to the team, curved solid-state structures have potential applications in innovative electronic, spintronic, and superconducting devices. Curvature effects can also promote, in a semimetallic nanowire, the EMERGING TECHNOLOGY The DOE along with the DOE’s National Nuclear Security Administration announced the achievement of fusion ignition at Lawrence Livermore National Laboratory (LLNL), a breakthrough that will pave the way for advancements in both national defense and clean power. On Dec. 5, 2022, a team at LLNL’s National Ignition Facility conducted the first controlled fusion experiment in history to reach “scientific energy breakeven,” producing more energy from fusion than the laser energy used to drive it. llnl.gov. BRIEF generation of topological insulating phases that can be exploited in nano- devices relevant for quantum technologies, like quantum metrology. In the case of magnetism, curvilinear geometry directly forges the magnetic exchange by generating an effective magnetic anisotropy, thus prefiguring a high potential for designing magnetism on demand. Contributing researcher Ivan Vera-Marun from the U.K.’s University of Manchester explains that “nanoscale curvature and its associated strain result in remarkable effects in graphene and 2D materials. The development in preparation of high-quality extended thin films, as well as the potential to arbitrarily reshape those architectures after their fabrication, has enabled first experimental insights into how next-generation electronics can be compliant and thus integrable with living matter.” The new work outlines the methods needed to synthesize and characterize curvilinear nanostructures and highlights key areas for future developments of curved nanoelectronics. www.manchester.ac.uk. These flexible solar cells consist of very thin layers and include a compound composed of copper, indium, gallium, and selenium. Courtesy of Empa. This soft robot, equipped with SHeaLDS can detect damage and heal itself. To create fusion ignition, laser energy converts into x-rays in a hohlraum, which then compresses a fuel capsule until it implodes, creating a hightemperature, high-pressure plasma.
1 2 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 *Member of ASM International POINT-OF-NEED INNOVATIONS: METAL ADDITIVE MANUFACTURING AND REPAIR Paul G. Allison, J. Brian Jordon,* M. Brady Williams, Troy Pierson, and Ryan Kinser Point-of-Need Innovations Center, Baylor University, Waco, Texas Timothy W. Rushing U.S. Army Engineer Research & Development Center Brandon J. Phillips DEVCOM Aviation & Missile Center Kevin J. Doherty DEVCOM Army Research Laboratory Additive friction stir deposition uses secondary feedstocks such as machine chips and damaged components to make in-field repairs at the point of need. A D D I T I V E M A N U F A C T U R I N G 1
1 3 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 As the global scientific and engineering community struggles with minimizing logistical and economic challenges for metal part production and repair, there is a strong demand to incorporate more sustainable additive manufacturing (AM) solutions on demand at the location of use, or point-of-need. Within the United States, multiple government agencies seek innovative ways to reduce the strain on supply chain, natural resources, and active sustainment. AM is sought as a pathway to these goals, which provides: (1) resource management in that less waste is produced per component, (2) economic-design optimization to develop complex, yet lightweight parts to improve efficiency, and (3) reduction in chemical byproducts typical of traditional manufacturing[1]. More recently, proposed efforts have included multiple investigations on AM as a means of recycling[2]. Current hailed objectives have focused on the most popular additively manufactured material, plastic[3]. The advancements in these methods have developed the capability to employ polypropylene as a feedstock material, which is most commonly known for use as water bottles[4]. With the success of improving overall sustainability, and thus active readiness, these same agencies have expanded the desire for stronger materials. The Committee on Armed Services[5] specifically outlines particular interests in structural materials such as metals, ceramics, and composites, which are envisioned as recyclable lowcost, low logistical, and high strength to be utilized in military vehicle applications. As such, multiple means have been proposed to attempt to accomplish these challenges for both environmental and practical purposes. Currently, the Strategic Environmental Research and Development Program (SERDP) has been supporting multidisciplinary research to recycle unwanted waste materials, or secondary feedstocks, through low-power approaches that are applicable to austere locations and traditional manufacturing environments. From this SERDP research, a new direct additive recycling (DAR) is responsible for 1% of annual greenhouse gas emissions, and production of aluminum from ore-bauxite consumes more energy than any other metal[7]. In the lifetime of an aluminummade product, researchers have reported that 1 kg of aluminum in a car reduced CO2 emission by an equivalent 19 kg. This environmental benefit is also compounded by the 5 to 7% fuel savings that can be realized for every 10% weight reduction through substituting aluminum for heavy steel-based alloys[8]. How- ever, the greenhouse gas emissions per kilogram production of primary aluminum range from 5.9 to 41.1 kg CO2 equivalent and the “break-even point” of vehicle lightweighting in terms of its required lifespan ranges from 50,000 to 250,000 km[7]. Estimates indicate that recycling 1 kg of aluminum can potentially save 4 kg of bauxite, 2 kg of chemicals and 7.5 kWh of electricity[9]. As reported in literature[8] and presented in Fig. 1, the average energy consumption paradigm has evolved for using various waste streams (machine chips and damaged scrap) as feedstock for metal AM and repair. The focus of the initial research was aluminum alloys, which saw significant advances; however, preliminary studies show significant promise for the adaptation of these techniques to hard alloys including steel castings, wrought high strength steels, and even titanium alloys. DAR MOTIVATION FOR ALUMINUM ALLOYS Aluminum is the most widely used metal in the aerospace and automobile industries because of its combination of lightweight and other desirable properties[6]. With increasing demand for aluminum around the globe, the scientific communityhas estimated that nearly 80 new smelters with 400 kt production capacity each must be established. Globally aluminum production Fig. 1 — Energy requirements for production of (a) primary aluminum- 113 GJ/t and (b) secondary aluminum- 13.6 GJ/t. Recreated fromRef 8.
1 4 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 When compared to other metal AM methods, the AFSD process does not suffer from significant tool wear issues for aluminum and magnesium alloys since only the AFSD feed rod is consumed during the deposition. In addition, the AFSD process provides a path for reducing costs by alleviating the need for hot isostatic press (HIP) and heat affected zone (HAZ) rework, post-production processes typically required for other advanced manufacturing techniques. Other significant advantages of the solid-state AFSD process are the wide variety of materials that can be deposited, the ability to join or repair dissimilar materials, and the ability to produce functionally graded components. During the AFSD process, maximum temperatures are maintained well below the liquidous state (Td < Tm) of the respective deposited material, preventing solid-liquid-solid phase transformations that may result in material defects such as hot-cracking during fusion-based depositions. Additionally, the lower temperatures during the solid-state deposition allow for a lower amount of distortion for the substrate, to produce primary aluminum from bauxite is approximately eight times greater than energy required for recycling aluminum. Because of the drastic reduction in energy consumption and greenhouse gas emissions, recycling aluminum scrap/waste has found high prominence. At present, conventional recycling of aluminum scrap/cast waste involves segregation, cleaning, shredding, melting, and subsequent casting as ingots, or in some cases, structural members. Production of aluminum granules and powders from scrap/ waste using powder metallurgy is another recycling method, although less common[10]. This secondary recycling process also requires several stages of cleaning, sorting, and preparation of the aluminum scrap/waste. For example, in recycling aluminum machine chips, a relatively clean and high-quality feedstock is required[11], while in cast aluminum alloy recycling production, the scraps/waste are received fromendof-life products and can tolerate high degree of debris and additives[12]. Once aluminum has been recycled, it generally does not retain the same chemical composition or mechanical properties as the feedstock and hence additional secondary manufacturing processes are required to produce required alloys. ADDITIVE FRICTION STIR DEPOSITION To address the shortcomings and achieve the goal of complete recyclability of aluminum scrap/waste, a transformative hybrid solid-state additive manufacturing process, additive friction stir deposition (AFSD), has emerged (Fig. 2). The novelty of AFSD is that it uses a low-power technology (~7 kW) and combines the advantages of AM and microstructure refinement into a single process, allowing fabrication of near-net shape small and large components with similar chemical composition as the feedstock material. AFSD is a thermomechanical non-melting process that can be performed in any ambient environment and has no emission or generation of waste during or after the deposition since the waste chips from machining of near-net shape depositions can be recycled back through the AFSD process. Preliminary analysis reveals that recycling using the AFSD process consumes 77% less energy as compared to existing recycling technologies. Recent research has found several unique advantages of using AFSD to recycle aluminum secondary feedstocks in addition to the energy savings and reduction in greenhouse gas emissions. When recycling secondary feedstocks such as machine chips and damaged strips of metal, the AFSD process has been demonstrated to breakup inclusions and constituent particles because of the high shear stresses and frictional heat generated during processing. Once broken into smaller fractions, these inclusions are widely dispersed throughout the metal matrix which aids in the establishment of a robust metallurgical bond between deposited layers. This means that the waste products do not require the same level of sorting or cleaning that are required for traditional recycling methods but result in superior parts[14–22]. Fig. 2 —Direct additive recycling paradigmdemonstrated to repair an aluminum alloy (AA) part from secondary feedstock (metal strips and compactedmachine chips) at a forward operating base (FOB) using the AFSD solid-state additive manufacturing process. Top le image fromRef 13.
1 5 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 round and square feedstock. These machines run off the same FSW platforms Bond has been providing to customers for several years, but now create a hybrid AFSD machine capable of FSW, AFSD/FSAM, and machining with temperature and force feedback controls complementing displacement control processing. Generically, the variable process parameters are tool geometry, spindle rotational speed, filler feed rate, and tool traverse rate. The tool design has been shown to have a large impact on the deposited layer thickness, and thus the volumetric deposition rate. The next most significant process parameter controlling the volumetric deposition rate is the traverse rate. The maximum traverse speed for a defect-free deposition is a function of tool design, filler feed rate, and spindle rotational speed. While the spindle rotational speed is the most significant parameter in controlling the temperature for a given tool, the filler feed rate is the most significant parameter in controlling the pressure for a given tool plunge depth. Hence, the interdependent process parameters need to be optimized for a in comparison to fusion-based additive manufacturing techniques, e.g., laser powder bed fusion (L-PBF) and electron beammelting (EBM). The lower severity of thermal cycles reduces the residual stresses within the deposition and substrate, thus, residual stress induced distortion is minimized[23]. The quality of the desired microstructure and fabrication rates are established through flexible process parameters such as spindle geometry, spindle rotation speed, filler feed rate, and tool traversing rate. COMPARISON TO OTHER PROCESSES It is important to note that although AFSD has the advantage of providing increased deposition rates in an open atmosphere (certain materials like Ti alloys require shielding) with low energy there are certain disadvantages. Finish machining is required when using AFSD since components are generally more near net-shape when compared to other AM methods. Figure 3 compares the build accuracy and build rate of AFSD, directed energy deposition (DED), and powder bed fusion (PBF). The current nascent state of the AFSD technology is commercially available from MELD Manufacturing and is constrained to square cross-section feedstocks. The process is controlled by operator written, traditional CNC G-code via the commercial MELD Manufacturing software, which translates the machine code into 3-axis movements and deposition rates. During operation, the software generated timestamped machine feedback at 1 Hz is subsequently analyzed for temporal and material consumption examination. Tabulated position data for the machine head and linear actuator are determined by position sensors located in the AFSD machine, which are used to determine absolute distance and material consumption. Although not equipped to provide feedback control, force measurements are recorded at 1 Hz via electrical current required to maintain feedstock deposition velocity. Companies such as Bond Technologies provide alternative AFSDmachine platforms, referred to by Bond Technologies as friction stir additive manufacturing (FSAM), machine platforms that are now capable of depositing both Fig. 3 —Comparison of build accuracy versus build rates for additive friction stir deposition, powder bed, and direct energy deposition.
1 6 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 given tool design tomaximize the deposition rate for each material. SUCCESS FROM VARIOUS WASTE STREAMS To date, research has identified key barriers for deposition of recycled material. By learning from new feedstock deposition strategies, successful depositions for both recycled machine chips and strips of damaged material feedstock were achieved as depicted in Fig. 4 and detailed microstructure and resulting mechanical behavior in the open literature[15-16,24]. To achieve adequate compaction and deposition of machine chip feedstocks shown in Fig. 4, the chips required an additional processing step of ball milling to sizes less than 30 mm regardless of whether the chips were compacted into a rod fed AFSD machine or directly fed through an AFSD machine outfitted with an auger feeder. From a forward operating base (FOB) standpoint, the auger system is incapable of depositing hard alloys such as steel or titanium alloys due to wear and fracture toughness issues and would require time intensive machine modifications to switch between processing auger feedstock or rod feedstock. Therefore, the use of a continuous chip recycling machine as discussed later would be a more viable option to mitigate machine downtime from swapping out AFSD components. Alternatively, strips of material instead of monolithic rods can be loosely deposited by the AFSD process by creating stacks of thin strips of a material together to fill the approximate geometry of traditional AFSD feedstock. With these stacked strip recycling depositions, exterior contaminants such as sand or other abundance of high friction particles will result in jamming of material in the tool and require extensive cleaning with machine downtime. Interestingly, the current SERDP research project was able to demonstrate the viability of depositing the strips of material with the non-skid coating or even internal sand embedded between layers to create a successful MMC deposition. Here, these depositions highlight the robustness of the process to fabricate parts using contaminated feedstock material. POINT-OFNEED DAR IN ACTION C u r r e n t l y , AFSD provides a complementary process that can overcome barriers created by liquid-solid phase transformations of fusion-based AM processes, but there are still limits to the nascent technology. Specifically, additional research and development are required for items such as tooling advancement s , process monitoring and feedback controls, and automatic feeding of solid rod feedstock. For example, in the AA6061 AFSD build shown in Fig. 5 that was a 64 mm tall build with a length of 152.4 mm, the actual deposition rate was 0.25 kg/ hr compared to the theoretical deposition rate of 1.03 kg/hr. The difference between the two values is that only two layers were able to be deposited per rod of feedstock. Therefore, the machine and tool had to cool down for a certain amount of time before the operator could load new feedstock rods. Additionally, since the machine was only able to deposit in position control there was no spatial-temporal information to provide feedback control from subsequent heat generation as the build height increased to the maximum height. The successful completion of the SERDP project has demonstrated the ability for DAR of aluminum alloy secondary feedstocks. As AFSD is still in the early maturation stages there is still additional development required to transition this technology to the field. Particularly, automatic feeding is currently in development, which will create significantly improved microstructures and mechanical behavior by eliminating transient regions of starting/stopping the process to reload new feedstock. The AFSD process is at a stage where there are still more scientific discoveries to make as the process matures, but the process does offer key immediate benefits for production repair, specifically by fabricating and repairing long lead time large aluminum alloy components at production facilities such as military depots. However, since fabricating the square feedstock is a significant limitation from a time and material standpoint, the ability to further investigate round feedstock depositions is highly beneficial to the user community. Limited investigations to date for round feedstock demonstrate the ability to produce similar AFSD builds and properties to builds fabricated with square feedstock depositions (Fig. 6). The preliminary work in Fig. 6 comparing round and square feedstock Fig. 4 —Successful AFSD depositions from recycled feedstock including compactedmachine chips, loose machine chips, and strips of damagedmaterial.
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