JULY/AUGUST 2022 | VOL 180 | NO 5 19 24 33 Production of Ancient Iron Addressing AM Challenges for Metal Components iTSSe and HTPro Newsletters Included in This Issue DED FOR LARGE NEAR-NET SHAPE PARTS ADDITIVE MANUFACTURING P. 13
JULY/AUGUST 2022 | VOL 180 | NO 5 19 24 33 Production of Ancient Iron Addressing AM Challenges for Metal Components iTSSe and HTPro Newsletters Included in This Issue DED FOR LARGE NEAR-NET SHAPE PARTS ADDITIVE MANUFACTURING P. 13
27 IMAT 2022 SHOW PREVIEW IMAT—the International Materials Applications & Technologies Conference and Exhibition—and ASM’s annual meeting will be held in New Orleans, September 12-15. DIRECTED ENERGY DEPOSITION MOVES OUTSIDE THE BOX Judy Schneider and Paul Gradl Metal additive manufacturing has steadily progressed over the past decade, with today’s directed energy deposition processes enabling rapid builds of large structures in near-net shape—and with minimal machining required to achieve final dimensions. 13 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 U L Y / A U G U S T 2 0 2 2 2 Cladding as a directed energy deposition method. Courtesy of NASA/DM3D. On the Cover: 65 ASM NEWS The latest news about ASM members, chapters, events, awards, conferences, affiliates, and other Society activities. 12 SUSTAINABILITY Researchers look at ways to make plastic in a more sustainable way and also use plastic waste to absorb emissions.
4 Editorial 6 Research Tracks 7 Machine Learning 8 Metals/Polymers/Ceramics 10 Testing/Characterization 12 Sustainability 79 Editorial Preview 79 Special Advertising Section 79 Advertisers Index 80 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. 180, No. 5, JULY/AUGUST 2022. Copyright © 2022 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 Publishers Press Inc., Shepherdsville, Ky. 19 ANCIENT IRON PRODUCTION AND PROCESSING IN THE OLD WORLD Omid Oudbashi, Ümit Güder, and Russell Wanhill A look at processing and production of iron during the Iron Age, 1200 to 500 B.C., including early unintentional forms of steel. 24 TECHNICAL SPOTLIGHT ADDITIVE MANUFACTURING PRESENTS NEW CHALLENGES FOR METAL COMPONENTS A look at how companies in regulated industries can test materials to produce higher quality metal components with additive manufacturing. 33 iTSSe The official newsletter of the ASM Thermal Spray Society (TSS). This timely supplement focuses on thermal spray and related surface engineering technologies along with TSS news and initiatives. FEATURES JULY/AUGUST 2022 | VOL 180 | NO 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 U L Y / A U G U S T 2 0 2 2 3 19 49 33 24 49 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 Welcome to our IMAT show issue with a focus on additive manufacturing (AM). The technology around AM continues tomature and find new applications. And new solutions are being discovered every day to overcome previous limitations. One of the main challenges with AM is production time. A standard fused deposition modeling printer averages 100 mm/hour. And we are all familiar with the slow, meditative cadence of a typical AM build. Yet, if printing is accelerated, vibrations occur, leading to poor quality and even misshapen components. Entire batches may need to be scrapped. To address this problem, Dr. Chinedum Okwudire, a University of Michigan (U-M) professor and his students launched new software that doubles the typical 3D printing speed. Their software, called FBS for Filtered B Splines, performs this veritable magic by compensating for the usual vibrations caused by acceleration. “Say you want a 3D printer to travel straight, but due to vibration, the motion travels upward. The FBS algorithm tricks themachine by telling it to follow a path downward, and when it tries to follow that path, it travels straight,” Okwudire explains. Another development in the AM sector addresses previous limitations regarding component size. Our lead article shows how directed energy deposition now allows for extremely large structures to be built more rapidly and with minimal machining. The AM space keeps evolving and expanding. What other developments are on the horizon? To learn about additional AM research, attend IMAT 2022, which will feature three days of programming on additive along with many other materials topics. In line with the conference theme of the Circular Materials Economy, Dr. Mrityunjay Singh, FASM, will deliver a special lecture on Tuesday morning covering how AM is disrupting global supply chains and enabling sustainable materials development. See our IMAT Show Preview on page 27 for details of this September conference being held in New Orleans. To provide more options for our attendees, the event is co-located with the Thermal Spray & Surface Engineering (TSSE) Forum and Exposition. More information on TSSE programming can be found on page 34. An exciting highlight of ASM’s annual event this year is the new Fellows Induction Ceremony on Monday evening, September 12. There you can meet three years’ worth of the newest ASM Fellows, fromClasses 2020, 2021, and 2022. All ASM members and guests are welcome. This unique, first-time event is in addition to the traditional ASM Awards Dinner. We hope to see many of you at both events. Like the U-M students who are making a name for themselves with their new software launch, our students and emerging professionals have research of their own to share in New Orleans. Presentation and program opportunities for both sets of these next-gen engineers will be available at IMAT. The Emerging Professionals Committee describes their lineup in the ASM News section of this issue. We look to them—as their careers unfold and mature—to devise the next set of novel solutions to AM and many other materials challenges. 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 U L Y / A U G U S T 2 0 2 2 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 Jan Nejedlik, 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 Scott Olig, U.S. Naval Research Lab 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 Judith A. Todd, President and Chair of the Board David B. Williams, Vice President Diana Essock, Immediate Past President John C. Kuli, Treasurer Burak Akyuz Ann Bolcavage Elizabeth Ho man Navin Manjooran Toni Marechaux U. Kamachi Mudali James E. Saal Priti Wanjara Ji-Cheng Zhao Sandra W. Robert, Secretary and Executive Director STUDENT BOARDMEMBERS Shruti Dubey, AndrewRuba, David Scannapieco Individual readers of AdvancedMaterials & Processes may, without charge, make single copies of pages therefrom for personal or archival use, or may freelymake 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. DISCOVERING SOLUTIONS AT IMAT U-M’s high-speed 3D printing. Courtesy of E. Dougherty.
INTRODUCE DEEP LEARNING AI TO YOUR ADDITIVE MANUFACTURING R&D AND QC Hybridization of DL and traditional imaging creates advantage. SPONSORED CONTENT For more information on deep learning image analysis solutions for AM, contact MIPAR Software at support@mipar.us / 614.407.4510 / www.mipar.us. In today’s fast-moving environment, reducing project turnaround time, accelerating research and development, and meeting productivity targets, all while reducing operating cost can be challenging without a smart automated approach. To avoid product recalls, meet increased customer demands, and continually innovate, a thorough investigation of materials’ microstructure is key. Defect, inclusion, and grain size analysis are only a few approaches that can give meaningful insights into the quality of products. Modern research and quality control have the unique challenge of working with real world, imperfect micrographs that require a flexible tool suite. MIPAR Image Analysis combines customized algorithms and powerful deep learning systems to produce technology able to perform sophisticated structure investigation. Whether of titanium, copper, steel, aluminum, or ceramics, MIPAR’s software allows for automated micrograph analysis that streamlines data analytics, improves data quality, and offers new layers of information. Automation re- duces operator error and improves professional productivity. A primary challenge in modern R&D and QC processes is that the manufacturing environment is increasingly driven by stringent efficiency requirements in the name of productivity. Guaranteeing product quality often runs contrary to pushing the bottom line, meaning defect and contaminant analysismust be carried out quickly as well as effectively. Automation and digital integration are central to the push for greater productivity in manufacturing environments. The concept of automating production typically brings to mind the robotic arms of assembly lines, but manufacturers are just as interested in software solutions that accelerate critical processes throughout the manufacturing pipeline. Deep learning is one such solution. Did you know that more and more companies are using deep learning to double check the material quality provided by suppliers? Be ahead of your customers by introducing these capabilities in-house. Improve your customer satisfaction, avoid rework, while reducing the operational cost. What is Deep Learning? The aimof deep learning AI (artificial intelligence) is to teach software to adapt to your own micrographs. It works in the presence of varying contrasts and feature texture, as well as sample preparation artifacts. As little as four images can be used to train an application specific solution. This can be done with minimum training and no programming expertise. This technology has had a profound role in developing the latest micrograph analysis solutions in the additive manufacturing (AM) space. Not only does AM imagery suffer from the usual challenges of varying contrast/ lighting, sample prep noise, etc., it offers especially complex microstructural features, often with extremely poor contrast due to the rapid cooling rate and high deformation processes involved in part fabrication. While humans have proven adept at identifying these features by eye, traditional automated software has strug- gled handsomely. Breakthrough Solutions MIPAR’s unique hybridization between deep learning and traditional image processing has allowed for rapid custom development of breakthrough solutions for automated AM materials analysis and inspection. Examples include melt pool quantification, defect classification, layer thickness profiling, ultrafine phase measurement, complex grain sizing, virtual powder precursor sieve analysis, and part porositymapping, just to name a few. Fully automated particle detection and satellite classification. Enables size and shape distribution per particle class. Advanced automation of complex twinned grain size analysis in aged additively manufactured component.
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 U L Y / A U G U S T 2 0 2 2 6 MAKING MAPS FOR METAL ELECTROLYSIS A team of researchers from MIT, Cambridge, Mass., and SLAC National Accelerator Laboratory, Menlo Park, Calif., are mapping what occurs at the atomic level during metal electrolysis, a process in which a metal oxide is bombarded with electricity to create pure metal with oxygen as the byproduct. They say their work could lead to more efficient and environmentally friendly processes for producing metals such as lithium, iron, and cobalt. By making maps for a wide range of metals, the scientists not only determined the metals that should be easiest to produce using metal electrolysis, but also identified barriers that hinder the efficient production of others. RESEARCH TRACKS The research could also boost development of metal-air batteries such as lithium-air, aluminum-air, and zinc-air batteries. These are similar to the lithium-ion batteries used in today’s electric vehicles, and they have the potential to electrify aviation because of their much higher energy densities. Metal-air batteries are not yet on the market due to a variety of problems, including inefficiency. All of the research was conducted using supercomputer simulations that explored different scenarios for the electrolysis of several metals, each involving different catalysts. The team’s new map is essentially a guide for designing the best catalysts for each metal, say researchers. web.mit.edu. NEURAL NETWORK PREDICTS STEEL PART LIFETIMES A team of researchers from Russia, Turkey, Canada, and Italy created an artificial deep neural network that is able to predict the lifetime of a component made of AISI 1045 steel—along with choosing the optimal coating and its thickness. First, the scientists conducted a series of MIT researcher Jaclyn Lunger is detailing the atomic-level reactions behind an eco-friendly way to make metals. Courtesy of Yang Shao-Horn/MIT. physical experiments on steel parts. Approximately 23% of the data was used to train the neural network while the rest was used for testing and validation of the resulting predictions. The team tried out several neural networks, with different numbers of inner layers and neurons in each layer. Nearly 99% accuracy was reported for the best neural network’s predictions. Nickel, hardened chromium, and the galvanization process were used as protective coatings in the model. Further, the scientists were able to determine the optimal protective coating, which turned out to be a 10-15 µm layer of nickel or zinc. Hardened chromium was found to reduce the fatigue lifetime of steel. The team included researchers from RUDN University, Russia, Karabuk University, Turkey, Ontario Tech University, Canada, and the Polytechnic University of Milan. www.rfbr.ru/rffi/eng. An international team of scientists is using an artificial deep neural network to predict the stability of steel parts and find the best protective coating. Scientists from Texas A&M University, College Station, and Yonsei University, Seoul, discovered a helicoidal-shaped defect in layered polymers, revealing how solvents can diffuse through layers and produce color changes. Because stimuli-interactive structural color holds immense potential for devices such as health sensors and human-interactive electronics, controlling the lateral spacing or amount of helicoidal defects could be a critical factor in future applications, say researchers. tamu.edu, www.yonsei.ac.kr. BRIEF
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 U L Y / A U G U S T 2 0 2 2 7 MACHINE LEARNING | AI PREDICTING BATTERY LIFE WITH MACHINE LEARNING Researchers at the DOE’S Argonne National Laboratory, Lemont, Ill., are using machine learning to predict the lifetimes of a wide range of battery chemistries. By using experimental data from a set of 300 batteries representing six different chemistries, the team can accurately determine how long various batteries will continue to cycle. The study relied on extensive experimental work done at Argonne on a range of battery cathode materials, especially the lab’s patented nickel-manganese- cobalt-based cathode. “We had batteries that represented different chemistries, that have different ways that they would degrade and fail,” says computational scientist Noah Paulson. “The value of this study is that it gave us signals that are characteristic of how different batteries perform.” Paulson believes the machine learning algorithm could accelerate development and testing of battery materials. “Say you have a newmaterial, and you cycle it a few times. You could use our algorithm to predict its longevity, and then make decisions as to whether you want to continue to cycle it experimentally or not,” he says. “One of the things we’re able to do is to train the algorithm on a known chemistry and have it make predictions on an unknown chemistry.” Further study in this area could potentially guide the future of lithium-ion batteries, adds Paulson. anl.gov. AI ASSISTANCE UP FOR DEBATE A team of researchers from Brookhaven National Laboratory, Upton, N.Y., the University of Liverpool in the U.K., and Ruhr University Bochum in Germany developed a new artificial intelligence (AI) agent called the x-ray crystallography companion agent (XCA) that assists scientists by classifying x-ray diffraction (XRD) patterns automatically during measurements. XCA uses a collection of individual AIs that are trained semi- independently of each other. Each agent has a slightly different weighting within its neural network. When presented with data, each AI “votes” based on its own interpretation and analysis. Once the AIs cast their final votes, the XCA approach uses a vote tally to interpret what the most likely atomic structure is and to suggest how confident the researchers should be of the AI analysis. Essentially, XCA is a group of AIs that debate each other while analyzing live-streaming x-ray data. Consensus among the ensemble implies confidence in the results because differing viewpoints still result in a common conclusion. However, strong disagreement can suggest that the analysis was poorly posed, and researchers should reexamine their assumptions. Unlike many other AI approaches in this field, this unique “ensemble voting” approach provides both predictions and uncertainties. In effect, this makes the approach a digital expert in XRD analysis. This approach demonstrates how AI and human researchers can work together to address scientific challenges such as developing new energy technologies and supporting human health. The study found that XCA can classify the materials as effectively as a human expert, but in fractions of a second. bnl.gov. A newmachine learning technique could reduce the cost of battery development. AI agents observe streaming x-ray data, argue among themselves, and vote to establish both classification and uncertainty in the prediction—offering an educated guess about the atomic structure of the material under analysis. Courtesy of BNL.
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 U L Y / A U G U S T 2 0 2 2 8 METALS | POLYMERS | CERAMICS Expanite, Denmark, achieved ISO 14001 certification, the international standard for implementing an environmental management system to measure and reduce environmental impact. The company produces a technology that prevents wear, galling, and corrosion of components in stainless steel or titanium by hardening the material in a pure gas environment with no toxic waste. expanite.com. Norman Noble Inc. is building a new 51,000-sq-ft corporate headquarters in Highland Heights, Ohio, to be ready later this year. The company specializes in micromachining Nitinol implants to meet its medical OEM clients’ requirements for Nitinolbased products such as structural heart implants and neurovascular devices. nnoble.com. BRIEFS separations needed to recover rareearth elements and secure critical materials for clean energy technologies. Bastnaesite deposits in the U.S. are rich in rare-earth metals but must be mined and separated from unwanted minerals through chemical processes that are not well understood. Fundamental insights are needed to improve current recovery approaches based largely on trial and error. Greater efficiency offers cost-savings as well as benefits to the environment by decreasing mining and carbon impacts. According to the scientists, the path forward will require predictive modeling to help discover the best candidates for more efficient separations. ornl.gov. New research describes howmicroscopic crystals grow and change shape in molten metals as they cool. Courtesy of MaksimGusev. BREAKING GROUND ON STRONGER ALLOYS In a breakthrough for alloy research, scientists from the U.K.’s University of Birmingham have detailed how microscopic crystals grow and change shape in molten metals as they cool. Their work paves the way for improving the tensile strength of alloys used in casting and welding. The researchers used high-speed synchrotron x-ray tomography to image the changing crystal structures in molten alloys as they cool. Researchers say that as aluminumcopper alloy cools, the solidification process starts with the formation of faceted dendrites, which are formed by a layer-by-layer stacking of basic units that are just micrometers in size. These units start out as L-shaped and stack on top of each other like building blocks. As they cool, they change shape and transform into a U-shape, and finally into a hollowed-out cube, while some of them stack together to form beautiful dendrites. “The findings from this new study provide a real insight intowhat happens at a micro-level when an alloy cools and show the shape of the basic building blocks of crystals in molten alloys,” lead researcher Biao Cai explains. “Crystal shape determines the strength of the final alloy, and if we can make alloys with finer crystals, we can make stronger alloys.” www.birmingham.ac.uk. RECOVERING RARE-EARTH ELEMENTS Using state-of-the-art spectroscopy methods, researchers at Oak Ridge National Laboratory, Tenn., are gaining a better understanding of chemical Researchers shed light on chemical separations to recover rare-earth elements. Courtesy of Ben Doughty/ ORNL, U.S. DOE. RESHAPING POLYMERIC THEORY A longstanding mystery surrounding a nanoscale structure called a double-gyroid was reported to be solved by polymer scientists at the University
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 U L Y / A U G U S T 2 0 2 2 9 of Massachusetts, Amherst. One of the most desirable shapes for materials scientists, and with a wide range of applications, double gyroids have historically eluded scientists’ understanding. This unique structure is comprised of a single layer that twists up into a saddle-shaped layer, which then fits into a cubic box in such a way that its surface area stays as small as possible—that’s a gyroid. A double-gyroid forms when a second material, also twisted into a gyroid, fills in the gaps in the first gyroid. Each gyroidal material forms a network of tubes that interpenetrates the other. Together, they form an enormously complex material that is both symmetrical on all sides, like many crystals, yet pervaded by labyrinthine channels, each formed from different molecular units. Because this material is a hybrid of two gyroids, it can be engineered to have contradictory properties. The research team built upon a previous theoretical model, adding a heavy dose of thermodynamics and a new approach to thinking about the packing problem—or how best to fill a finite container with material—borrowed from computational geometry and known as the medial map. The team’s updated theoretical model not only explains the puzzling formation of double-gyroids but holds promise for understanding how the packing problem works in a much broader array of self-assembled superstructures, such as double-diamonds and double-primitives—or even structures that have yet to be discovered. The end goal is to be able to engineer a wide variety of materials that take advantage of the double-gyroid’s structure and that can help advance a wide range of technologies from rechargeable batteries to light-reflecting coatings. umass.edu. In a double-gyroid, two materials (pictured as red and blue) interpenetrate each other. Courtesy of Reddy et al., Nature Communications, 2022.
1 0 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 U L Y / A U G U S T 2 0 2 2 extracellular fluid of the body, as well as in saline. They measured how much photoelectrical current was generated when they exposed the disks to light of various wavelengths. They also performed x-ray photoelectron spectroscopy to characterize the passive films that were naturally present on the surface of the titanium. “The reactivity of titanium with high corrosion resistance, as revealed in this experiment by its electronic band structure, is one of the primary reasons for its excellent biocompatibility among metals,” add the scientists. This research may lead to safer and less expensive implants for hip replacements or dental implants, because titanium is relatively rare and expensive. www.tmd.ac.jp/english. TESTING | CHARACTERIZATION STUDYING BATTERIES AT THE NANOSCALE Researchers at the National Renewable Energy Laboratory (NREL), Golden, Colo., are conducting groundbreaking experiments using x-ray diagnostics techniques to examine the structure of battery materials. There is a common consensus that x-ray imaging techniques hold the key to unlocking critical information about the performance of energy storage systems. With the anticipated addition of a new x-ray nanoscale computed tomography (nano-CT) scanner, NREL researchers will have the technology that enables them to get a clearer picture of energy materials than ever before. “This scanner expands our capabilities at NREL with a new spatial resolution of 50 nanometers, a limit otherwise only achievable at high-energy synchrotron x-ray facilities,” researcher Donal Finegan notes. Significant improvements to the resolution of nano-CT systems open the door to advances in how scientists understand the composition, architecture, and properties of battery materials. As the sample rotates, an x-ray beam creates 3D images with extreme resolution. Given the nondestructive nature of nano-CT, researchers can view changes as they occur in real time to understand the reactions within a battery during operation or cycling. nrel.gov. BIOCOMPATIBILITY OF TITANIUM Scientists from the Tokyo Medical and Dental University are studying the source of titanium’s biocompatibility when implanted into the body, as with hip replacements and dental implants. Using photoelectrochemical measurement and x-ray photoelectron spectroscopy, they find that its reactivity with the correct ions in the extracellular fluid allows the body to recognize it. This work may lead to longer lasting next-generation medical implants. Despite numerous studies on biological reactions with implanted materials, the reason for the biocompatibility of titanium remains poorly understood. The research team tested thin disks of titanium in a solution containing ions meant to mimic the Plastometrex, based in the U.K., received an Innovate UK SMART grant along with testing service providers ROSEN and Element Materials Technology, and the U.K.’s National Physical laboratory. Funds will be used to develop new products for nondestructive testing of metal components in the field. The company launched a benchtop testing device in 2020 and plans to release the portable version in 2023. The system will apply to all metallic materials and will be used to test the strength of a variety of critical metal assets. plastometrex.com. BRIEF A visual comparison of super-resolution microscopy imaging obtained by five trained networks. Image courtesy of npj Computational Materials. This graph shows the change in open circuit potentials (OCP) of titanium in Hanks and saline for 72 h. NOVEL ION BINDING With the help of a self-built ion microscope, researchers from Germany’s 5th Physical Institute of the University of Stuttgart verified a novel
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 U L Y / A U G U S T 2 0 2 2 1 1 binding mechanism forming a molecule between a tiny, charged particle and a gigantic Rydberg atom. The molecule exhibits a special feature—it consists of a positively charged ion and a neutral atom in a so-called Rydberg state. These Rydberg atoms have grown in size a thousand times compared to typical atoms. As the charge of the ion deforms the Rydberg atom in a very specific way, the bond between the two particles emerges. To verify and study the molecule, the researchers prepared an ultra-cold rubidium cloud, which was cooled down close to absolute zero at -273°C. In these ultra-cold atomic ensembles, the ionization of single atoms with laser fields prepares the first building block of the molecule—the ion. Additional laser beams excite a second atom into the Rydberg state. The electric field of the ion deforms this gigantic atom. Notably, the deformation can be attractive or repulsive depending on the distance between the two particles, letting the binding partners oscillate around an equilibrium distance and inducing the molecular bond. The distance between the binding partners is unusually large and amounts to about a tenth of the thickness of a human hair. An open vacuum chamber with the electric field control and the first lens of the ion microscope sitting in the center. Courtesy of Nicolas Zuber. A special ion microscope made this observation possible. It was developed, built, and commissioned by the researchers at the 5th Physical Institute in close collaboration with the workshops of the University of Stuttgart. In contrast to typical devices working with light, the researcher’s special ion microscope influences the dynamics of charged particles with the help of electrical fields to magnify and image the particles onto a detector. Next, the researchers aim to study dynamical processes within this unusual molecule. www.pi5.uni-stuttgart.de.
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 U L Y / A U G U S T 2 0 2 2 1 2 SUSTAINABILITY BRIEF MAKING PLASTIC MORE SUSTAINABLY Scientists at Cardiff University, U.K., report a new method of creating cyclohexanone oxime, a precursor to Nylon-6, a common plastic used in the automotive, aerospace, and medical industries. It is estimated that global production of Nylon-6 will reach around 9 million metric tons a year by 2024, prompting scientists to search for greener and more sustainable ways of producing cyclohexanone oxime. Currently, cyclohexanone oxime is produced industrially through a process involving hydrogen peroxide (H2O2), ammonia, and a catalyst called titanosilicate-1 (TS-1). The H2O2 used in this chemical process is producedelsewhere and needs to be shipped in before it can be used in the chemical reaction. This is a costly and carbon-intensive process that also necessitates the shipping of highly concentrated H2O2 to the end-user prior to dilution, which effectively wastes large amounts of energy used during concentration. Similarly, stabilizing agents often used to increase the shelf-life of H2O2 can limit reactor lifetime and often need to be removed before arriving at a final product, leading to further economic and environmental costs. To address this issue, the team devised a method where H2O2 is synthesized in-situ from dilute streams of hydrogen and oxygen, using a catalyst consisting of gold-palladium nanoparticles that are either directly loaded on to the TS-1 or on a secondary carrier. The method can produce yields of cyclohexanone oxime comparable to those seen in current commercial processes while avoiding the major drawbacks associated with commercial H2O2. www.cardiff.ac.uk. PLASTIC WASTE THAT ABSORBS CO2 Researchers at Rice University, Houston, led by chemist James Tour, discovered that heating plastic waste in the presence of potassium acetate produced particles with nanometer-scale pores that trap carbon dioxide molecules. According to the team, these particles can be used to remove CO2 from flue gas streams. “Point sources of CO2 emissions like power plant exhaust stacks can be fitted with this waste-plastic-derived material to remove enormous amounts of CO2 that would normally fill the atmosphere,” explains Tour. “It is a great way to have one problem, plastic waste, address another problem, CO2 emissions.” To make the material, waste plastic is turned into powder, mixed with potassium acetate, and then heated at 600°C (1112°F) for 45 minutes to optimize the nanoscale pores. The process produces a wax byproduct that can be recycled into detergents or lubricants. Pyrolyzing plastic in the presence of potassium acetate produces porous particles able to hold up to 18% of their own weight in CO2 at room temperature. The lab estimates the cost of carbon dioxide capture from a point source like post-combustion flue gas would be $21 a ton—far less expensive than the energy-intensive, amine-based process in common use to pull carbon dioxide from natural gas feeds, which costs $80- $160 a ton. Like amine-based materials, the sorbent can be reused. Additionally, it is expected to have a longer lifetime than liquid amines, cutting downtime due to corrosion and sludge formation. rice.edu. Researchers at the DOE’s National Renewable Energy Laboratory, Golden, Colo., created a solar cell with a record 39.5% efficiency under 1-sun global illumination. This is reportedly the highest efficiency solar cell of any type measured using standard 1-sun conditions. nrel.gov. Courtesy of Pixabay/CC0 Public Domain. Paul Savas feeds raw plastic into a crusher to prepare it for pyrolysis. Courtesy of Je Fitlow.
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 U L Y / A U G U S T 2 0 2 2 *Member of ASM International DIRECTED ENERGY DEPOSITION MOVES OUTSIDE THE BOX Metal additive manufacturing has steadily progressed over the past decade, with today’s directed energy deposition processes enabling rapid builds of large structures in near-net shape—and with minimal machining required to achieve final dimensions. A D D I T I V E M A N U F A C T U R I N G Judy Schneider, FASM,* University of Alabama in Huntsville Paul Gradl, NASA Marshall Space Flight Center Image courtesy of NASA/RPM Innovations.
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 U L Y / A U G U S T 2 0 2 2 Fig. 1 — Overview of fusion-based metal additive manufacturing processes. Metal additive manufacturing (MAM) processes have matured from their early use as rapid prototyping tools to producing today’s critical end-use components[1-4]. Since the early 2010s, an increasing number of MAM processes have emerged that were initially referred to by various acronyms[5]. ASTM Committee F42 on Additive Manufacturing Technologies undertook the task of standardizing the terminology by issuing ASTM Standard F2792-12a in 2012[6]. In the most general terms, fusion-based MAM processes are characterized in terms of feedstock and the energy source used to fuse or melt the feedstock into the desired component geometry. Figure 1 provides an overview of the fusion-based processes in which either a powder or wire feedstock is combined with an energy source that melts the feedstock to either create a new freeform part or add material to an existing part. The two main categories include powder bed fusion (PBF) and directed energy deposition (DED). In PBF, a focused beam is used to trace out the part according to a defined toolpath from a CAD model in a layer-by- layer method using either a laser (L-PBF) or an electronbeam(EB-PBF)[7,8]. DED can use either a powder feedstock integrated with a laser (LP-DED) or a wire feedstock with either a laser beam (LW-DED), an electric arc (AW-DED), or an electron beam (EBW-DED)[9-12]. Other solid state MAM processes exist, but are not the focus of this article. IN THE BOX VS. OUT OF THE BOX The two primary categories of MAM can be thought of as “in the box” for PBF versus “out of the box” for DED. Although the most highly cited “in the box” metal AM process is L-PBF, the size of the build chamber restricts the final size of the component. To eliminate this size constraint, “out of the box” DED processing has emerged, although some systems may use a large purge chamber to prevent oxidation and issues with reactive alloys. The ability to fabricate outside the box removes size constraints, but tradeoffs between feature and geometric resolution, build and post-processing time, component size, microstructure and resulting properties, and process availability must always be considered. Figure 2a highlights the increased build dimensions made possible by using DED compared to PBF. In contrast, Fig. 2b shows that as build size increases, the deposition rate also increases with a resulting reduction in feature size. Figure 3 showcases several largescale structures fabricated using MAM DED. A NASA HR-1 alloy channel wall nozzle with integral internal passages for a liquid rocket engine is shown in Fig. 3a, built using LP-DED. An aluminum tank structure built using AW-DED is shown in Fig. 3b. MULTIPLE MATERIAL CHOICES DED can build using a variety of alloys including those based on nickel, iron, copper, cobalt, titanium, and Fig. 2 — (a) Selection of AM processes based on overall build dimensions[12]; and (b) relationship between feature size and deposition rate[5]. (b) (a)
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 U L Y / A U G U S T 2 0 2 2 as titanium. Electron beam (EBW-DED) requires the part to be deposited within a vacuum chamber and is also used for reactive alloys. Regardless of the enclosed or open-air environment, an integral inert purge is typical through the center of the LP-DED nozzle or AW-DED and LW-DED deposition heads. The various DED processes allow additional degrees of freedom (5+) during deposition as compared to L-PBF, which is a 2+1 axis system. The deposition head can typically move in three axes with some systems allowing for tilt and rotate. Use of a kinematic robotic arm further increases the number Fig. 3 — Nozzle extensions fabricated using MAM DED illustrate the large-scale format: (a) LP-DED of NASA HR-1, 1.83 m tall x 1.5 mOD with 1 mm wall thickness and internal integral channels; and (b) AW-DED of aluminum tank for a launch vehicle. Courtesy of RPM Innovations Inc./NASA, and Relativity Space, respectively. Fig. 4 — Deposition heads can be mounted on either (a) robotic arms or (b) CNCmachines. Courtesy of NASA/DM3D Technology, and RPM Innovations Inc./NASA, respectively. aluminum, as well as refractory alloys[12-14]. DED also enables deposition of multiple materials within the same setup, providing unique design solutions to optimize component-specific requirements for thermal, electromagnetic, pressure, loading, and dynamic properties. Deposition rates for DED processes can approach 9 kg/hour depending on component geometry, greatly reducing manufacturing time compared to other methods. In addition, less material is wasted because parts can be built to near-net shape in contrast to the subtractivemachining required by forgings. LARGE-SCALE BUILDS The ability to print large-scale structures is enabled by integrating the MAM DED deposition head with either a robotic arm or CNC controller platform, as shown in Figs. 4a and b, respectively. Directly mounting the deposition head onto the appropriate platform allows operation in an open-air environment using only localized shielding gas to prevent oxidation. Several DED systems that use laser as an energy source are integrated with an enclosed structure to allow for a fully inert environment, necessary for reactive alloys such (b) (a) (b) (a)
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 U L Y / A U G U S T 2 0 2 2 DED processes allow for complex curvature component shapes to be built with nonsymmetric features such as those in Fig. 4b. In the powder-based DED processes, various nozzles can be used as illustrated in Fig. 5. They range from a coaxial configuration to multi-jet nozzles to vectored nozzles for internal cladding (Figs. 5a-c). Inert carrier gas is used to propel powder through the various nozzle configurations into the melt pool, creating the deposited bead. Figure 6a provides a schematic overview of the LP-DED system showing the powder feeders or hoppers. Use of multiple hoppers facilitates the build of bimetallic and functionally graded parts by varying the types of powder as well as the mixture ratios. Powder flow paths are illustrated in Fig. 6b for a coaxial nozzle and Fig. 6c for a vectored nozzle. Research is also being conducted using central wire or powder feed deposition nozzles with an annular laser beam or series of off-axis laser beams around the center axis[15]. Several of the processes that use wire feedstock are illustrated in Fig. 7. For these, the fusion source uses standard welding-based processes including metal inert gas (MIG), gas tungsten arc (TIG), laser beam (LW-DED), and electron beam (EBW-DED). In contrast to fusion welding, the arc and beam sources melt the wire into a free-form structure of the desired part geometry. trunnion table is often integrated within DED platforms adding tilt and rotational axes. These aspects of the MAM of axes and the size of the component as either the robot or part, or both, can be mounted on a moveable platform. A Fig. 5 — Various powder nozzles: (a) coaxial (continuous annulus); (b) multi-jet; and (c) vectored nozzle capable of depositing inside a 57-mm ID to a depth of 610 mm. Courtesy of RPM Innovations Inc. Fig. 6 — (a) LP-DED systemwith multiple powder feeders or hoppers[5]; (b) coaxial nozzle powder flow path; and (c) vectored nozzle powder flow path. (c) (b) (c) (a) (a) (b)
1 7 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 U L Y / A U G U S T 2 0 2 2 Wire-based processes feature the highest deposition rate, allowing large structures to be built rapidly with superior material usage efficiency. In addition to doing away with size constraints and boosting deposition rates, MAM DED processes offer further advantages. Because the substrate can be either a sacrificial build plate or part of the final component design, complex geometries can be built onto standard wrought shapes as shown in Fig. 8. By adapting the deposition heads to multi-axis robots and CNC systems, features can be locally added to parts— creating near-net shapes and significantly reducing final machining. In addition, use of hybrid DED equipment combines the ability to both add and subtract material in one process during component fabrication. Ancillary systems such as process monitoring and feedback loops can also be incorporated onto machine platforms. CONCLUSION MAM DED offers the ability to rapidly build large structures in near-net shape with minimal machining to final dimensions. Because MAM DED occurs outside of a box to locally deposit the feedstock, it provides more efficient material use. Additional cost savings can be achieved by deposition of complex geometries onto standard wrought product, which can be used as both the build plate and part of the finished component. Localized feature repair is also possible with DED. Use of hybrid additive/subtractive systems allows incorporation of machining tools to achieve design objectives such as dimensional control of internal passages and improved surface finish. ~AM&P For more information: Judy Schneider, professor, The University of Alabama in Huntsville, 320 Sparkman Dr., Olin B. King Technology Hall, Room N272A, Huntsville, AL 35899, judith. schneider@uah.edu. References 1. I. Gibson, D.W. Rosen, and B. Stucker, Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing, Springer New York, 2010. 2. W.E. Frazier, Metal Additive Manu- facturing: A Review, J. Mater. Eng. Perform., Vol 23, p 1917-1928, 2014. 3. D. Herzog, et al., Additive Manufacturing of Metals, Acta Mater., Vol 117, p 371-392, 2016. 4. D. Bourell, Introduction to Additive Manufacturing, Additive Manufacturing Processes, Vol 24, ASM Handbook, eds. D. Bourell, et al., ASM International, p 3-10, 2020, https://doi.org/10.31399/ asm.hb.v24.a0006555. 5. P. Gradl, et al., Metal Additive Manufacturing Techniques and Selection, Metal Additive Manufacturing for Propulsion Applications, eds. P. Gradl, et al., in Progress in Astronautics and Aeronautics, AIAA, ISBN: 978-1-62410626-2, 2022. 6. ASTM Standard F2792-12a, Stand- ard Terminology for Additive Manufacturing Technologies, ASTM Intl., West Conshohocken, Pa. 7. V. Bhavar, et al., A Review on Powder Bed Fusion Technology of Metal Additive Manufacturing, Additive Manufacturing Handbook: Product (a) Fig. 7 — Comparison of various arc-based processes that use wire: (a) metal inert gas (MIG); and (b) gas tungsten arc (TIG)[16]. Fig. 8 — Deposition of features onto standard bar stock. Use of additive/subtractive hybrid systems enables improvement of surface finishes after deposition. Courtesy of DMG Mori. (b)
1 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 U L Y / A U G U S T 2 0 2 2 Development for the Defense Industry, eds. A.B. Badiru, et al., p 251-253, CRC Press, Boca Raton, Fla., 2017. 8. H. Irrinki, et al., Laser Powder Bed Fusion, Additive Manufacturing Processes, Vol 24, ASM Handbook, eds. D. Bourell, et al., ASM International, p 209–219, 2020, https://doi.org/ 10.31399/asm.hb.v24.a0006621. 9. B. Dutta, S. Babu, and B. Jared, Science, Technology and Applications of Metals in Additive Manufacturing, Elsevier, Amsterdam, 2019. 10. An Introduction to Wire Arc Additive Manufacturing [2020 Update], AMFG, https://amfg.ai/2018/05/17/anintroduction-to-wire-arc-additivemanufacturing. 11. R.P. Martukanitz, DirectedEnergy Deposition Processes, Additive Manufacturing Processes, Vol 24, ASM Handbook, eds. D. Bourell, et al., ASM International, p 220–238, 2020, https://doi.org/10.31399/asm.hb.v24. a0006549. 12. P. Gradl, et al., Robust Metal Additive Manufacturing Process Selection and Development for Aerospace Components, J. Mater. Eng. Perform., https://doi.org/10.1007/s11665-02206850-0, April 18, 2022. 13. M. Perrut, et al., High Temperature Materials for Aerospace Applications: Ni-Based Superalloys and γ-TiAl Alloys, Comptes Rendus Physique, Vol 19, p 657-671, 2018. 14. J.A. Lee, Hydrogen Embrittlement of Nickel, Cobalt and Iron-Based Superalloys in Gaseous Hydrogen Embrittlement of Materials in Energy Technologies: The Problem, its Characterization and Effects on Particular Alloy Classes, p 624-667, Elsevier Ltd., 2012. 15. J. Zhang, et al., Analysis on Surface Finish of Thin-Wall Parts by Laser Metal Deposition with Annular Beam, Opt. Laser Technol., Vol 119, p 105605, 2019. 16. A.R. Nassar and E.W. Reutzel, Energy Sources for Fusion Additive Manufacturing Processes, Additive Manufacturing Processes, Vol 24, ASM Handbook, eds. D. Bourell, et al., ASM International, p 200–208, 2020, https://doi.org/10.31399/asm.hb.v24. a0006545.
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 U L Y / A U G U S T 2 0 2 2 1 9 A previous contribution to AM&P’s series on archaeometallurgy pre- sented a brief overview of production and process metallurgy for copper and silver alloys in the Old World[1]. Consistent developments of these technologies began around 3500 B.C., with bronzes becoming so important that the period from about 3300 to 1200 B.C. is commonly referred to as the Bronze Age. However, dates vary considerably according to geographical locations, and the Bronze Age is usually subdivided into Early, Intermediate, and Late periods, again with differing dates. Thisarticleprovidesabroadlysimi- lar overview for the Iron Age, which dates from approximately 1200 to 500 B.C. As before, the dates vary according to geographical locations and the relative sophistication of the production and processing techniques. A recent survey of the beginnings of iron in the Near East is given by Erb- Satullo[2]. He argues, like others, that iron- smelting technology was derived from the earlier developments of copper- smelting. This is very likely because the technology is complex, with many difficulties to overcome. This has been amp- ly demonstrated by modern-day experimental archaeometallurgy. These difficulties are described in this article. Before discussing ancient iron pro- duction and processing, note that without these and much later developments, beginning in the mid-18th century A.D., the Industrial Revolution would have been more problematic. Although there were many contributing causes of the Industrial Revolution, the development of large-scale iron and steel production, particularly for manufacturing industrial machines and tools, played a major role. ANCIENT IRON PRODUCTION The very beginning of iron smelting is uncertain. From the middle of the 19th century A.D. until the 1970s the concept of bowl furnace smelting was generally favored[3]. However, experiments have shown that this method is usually unsuccessful[4], but it is possible to obtain small amounts of partly consolidated iron using high-quality iron ores[5]. Regular iron smelting in the Old World was preceded by about 2000 years of copper and bronze production, by which time shaft furnaces for copper smelting were well-developed[1]. Thus, it might seem logical that iron smelting could be done in a similar fashion. However, there were, and are, major differences. Firstly, iron cannot be melted in a shaft furnace, but accumulates as a porous mixture of iron and slag called a “bloom.” Secondly, the operating conditions are (much) more complex. A schematic of an iron smelting shaft furnace and the various production stages and their locations is shown in Fig. 1. This schematic is based on experiments with a Hungarian shaft furnace design from the 10th century A.D.[6] In the present context this is anachronistic, but the design is generically representative, and the experimental study has the considerable advantage that it is combined with details of the production stages[6]. The schematic in Fig. 1 shows that shaft furnace iron smelting consists of pre-roasting iron ore and its subsequent reduction in a multistage process. The complexity of this furnace reduction would not have been recognized by the ancient ironmasters. Successful smelting also requires[7,8] (and would have required) an empirically determined optimum combination of the following parameters: furnace size, tuyère position, forced air volume, the type and size of ore particles, size of the charcoal, and the sequence of adding charcoal and ore[7,8]. Much more information about shaft furnace iron smelting is given in Ref. 6‒8. When a bloom is removed from the furnace it is spongy, consisting of a mixture of iron and slag. It is therefore first consolidated by hammering that squeezes out as much slag as possible. If too large to be hammer-forged by hand, the bloom is then split with a maul driven by sledgehammers. ANCIENT IRON PRODUCTION AND PROCESSING IN THE OLD WORLD A look at processing and production of iron during the Iron Age, 1200 to 500 B.C., including early unintentional forms of steel. Omid Oudbashi, Art University of Isfahan, Iran Ümit Güder, Alexander von Humboldt Fellow, Max-Planck-Institut für Eisenforschung, Germany Russell Wanhill, Emmeloord, the Netherlands
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