19 25 29 Capturing Accurate Stress-Strain Behavior Ultrasonic Fatigue Testing for AM Alloys SMST NewsWire and iTSSe Newsletter Included in This Issue APRIL 2022 | VOL 180 | NO 3 ARCHAEOMETALLURGY OF ANCIENT COPPER COINS MATERIALS TESTING/CHARACTERIZATION P. 14
19 25 29 Capturing Accurate Stress-Strain Behavior Ultrasonic Fatigue Testing for AM Alloys SMST NewsWire and iTSSe Newsletter Included in This Issue APRIL 2022 | VOL 180 | NO 3 ARCHAEOMETALLURGY OF ANCIENT COPPER COINS MATERIALS TESTING/CHARACTERIZATION P. 14
63 ASM NEWS The latest news about ASM members, chapters, events, awards, conferences, affiliates, and other Society activities. ARCHAEOMETALLURGICAL STUDY OF TWO ANCIENT COPPER COINS Patricia Silvana Carrizo and Peter Northover A scientific study of two copper coins from 1851 and 1853 reveals well-preserved symbols of a growing, newly independent Chile nation. 14 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 | A P R I L 2 0 2 2 2 Indenter for Rockwell testing with calibration block. Courtesy of Kimtaro/dreamstime.com. On the Cover: 72 3D PRINTSHOP 3D-printed concrete using recycled glass, life-sized printed statues, and more are described in this issue. 6 MACHINE LEARNING Researchers are finding new ways to use machine learning for inspecting 3D-printed metal parts and testing bulk materials.
4 Editorial 5 Research Tracks 6 Machine Learning 7 Process Technology 8 Metals/Polymers/Ceramics 10 Testing/Characterization 12 Emerging Technology 13 Nanotechnology 71 Editorial Preview 71 Special Advertising Section 71 Advertisers Index 72 3D PrintShop TRENDS INDUSTRY NEWS DEPARTMENTS Check out the Digital Edition online at asminternational.org/news/magazines/am-p ASM International serves materials professionals, nontechnical personnel, and managers wordwide by providing high-quality materials information, education and training, networking opportunities, and professional development resources in cost-effective and user-friendly formats. ASM is where materials users, producers, and manufacturers converge to do business. Advanced Materials & Processes (ISSN 0882-7958, USPS 762080) publishes eight issues per year: January/February, March, April, May/June, July/August, September, October, and November/December, by ASM International, 9639 Kinsman Road, Materials Park, OH 44073-0002; tel: 440.338.5151; fax: 440.338.4634. Periodicals postage paid at Novelty, Ohio, and additional mailing offices. Vol. 180, No. 3, APRIL 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 PROFILOMETRY-BASED INDENTATION PLASTOMETRY BRINGS SPEED AND ACCURACY TO METALLURGICAL R&D Bryer C. Sousa, Danielle L. Cote, Matthew A. Priddy, and Victor K. Champagne, Jr. This unique testing method offers economic benefits, sustainability advantages, and the potential to slash the time required to develop new alloys and processing recipes. 25 TECHNICAL SPOTLIGHT ULTRASONIC FATIGUE TESTING FOR ADDITIVELY MANUFACTURED METAL ALLOYS Compared with traditional fatigue testing, the ultrasonic method achieves much speedier results along with the ability to run extremely high test cycles in a reasonable time frame. 29 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 APRI L 2022 | VOL 180 | NO 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 | A P R I L 2 0 2 2 3 19 45 29 25 45 SMST NewsWire The official newsletter of the International Organization on Shape Memory and Superelastic Technologies (SMST). This biannual supplement covers shape memory and superelastic technologies for biomedical, actuator applications, and emerging markets, along with SMST news and initiatives.
4 Museum oil paintings just gained new advocates who are using novel testing methods to aid conservators in preserving these cultural treasures. Metal carboxylates knowns as “metal soaps” mysteriously form on paintings over time and damage the artwork. The phenomenon is most common with paints containing zinc and lead. Researchers at the National Institute of Standards and Technology (NIST) and the National Gallery of Art have teamed up to use infrared-light-based methods to identify the composition and distribution of themetal soaps. Various spectroscopy techniques such as photothermal induced resonance (PTIR) are used to gain a broader view of the chemical composition across various layers of paint samples. The PTIR method can provide chemical mapping to give conservators information about the initial factors causing the unusual formation and to help with preservation strategies. In another example of salvaging history, see our Research Tracks page for details on how the U.K. is using materials testing to refurbish a maritime icon, the HMS Victory. The first phase of the project involves extensive control tests on the metal fasteners, caulking, and paint that could be used to restore the 18th century warship. Only the materials proven most weatherproof will be deemed worthy of this royal project. From the British Isles we take you southwest to Chile, where our lead article offers an archaeometallurgical study of its ancient copper coins. Currency is a tangible artifact of any country’s heritage. Various figureheads, flowers, buildings, and mottos are minted to commemorate and elevate the values of that government. Materials characterization can serve a vital role in analyzing coins by providing insight into the raw materials, process, and equipment used in their minting. The resulting research can paint a rich picture of the culture, the peoples, and their values that created the coinage. Our members have been doing a bit of excavating and curating themselves lately. With the return of in-person conferences, our presenters are dusting off their travel bags. More importantly, they mined through the last two years of pandemic-stifled research and selected the gems—their own Mona Lisa’s—to submit as abstracts to our ASM conferences. Many ASM members attended the successful AeroMat event in Pasadena. Next up is the International Thermal Spray Conference in Vienna followed by the International Conference on Shape Memory and Superelastic Technologies in San Diego. You can find show previews for both events in the iTSSe and SMST NewsWire supplements. And then see page 1 to get jazzed for IMAT in New Orleans this September. Come to these events for the best-of-the-best research, reclaimed and honed from a global quarantine. Enjoy reviving your professional network. And thank your colleagues, anywhere in the world, who are applying materials science to noble conservation efforts. They are preserving culture—one coin, one ship, and one painting at a time. 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 | A P R I L 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 Madrid Tramble, Production Manager madrid.tramble@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. PRESERVING CULTURE “Gypsy Woman with Mandolin” by JeanBaptiste-Camille Corot. Courtesy of National Gallery of Art, Washington, adapted by NIST.
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 | A P R I L 2 0 2 2 5 MATERIALS TESTING PRESERVES MARITIME GEM Engineers at the University of Southampton and the National Museum of the Royal Navy (NMRN), both in the U.K., are collaborating to find the best materials to ensure the 18th century warship HMS Victory is weatherproof for another 50 years. The University’s nC2 Engineering Consultancy carefully designed a series of tests to assess the long-term performance of a range of paints, caulking, glues, and metal fastenings. The team is conducting a variety of tests on specially prepared samples. Tests are repeated using different RESEARCH TRACKS combinations of products on samples that have been treated to simulate the effects of wear, rain, sunlight, and time. For example, paint is tested for adherence to wood along with flexibility and water resistance. The same tests are then conducted on samples that have been aged using UV and salt spray, and samples that have been cooled or heated to specific temperatures. The first phase of the project is now underway. Using hundreds of oak samples prepared by NMRN’s shipwrights, nC2 is assessing the performance of nine different types of caulking and glue and five paint systems. A future phase will examine metal plank fastenings to see how they interact with the wood, paint, and caulking and examine any corrosion. www.southampton.ac.uk. PERKING UP PEROVSKITES Researchers at the University of California, Los Angeles along with colleagues from five other universities discovered the key reason why perovskite solar cells degrade in sunlight. Metal halide perovskites are of particular interest due to their promising application in energy-efficient, thinfilm solar cells. Perovskite-based solar cells can be manufactured at much lower costs than their silicon-based counterparts, making solar energy more accessible if the widely known degradation from long exposure to illumination could be addressed. A common surface treatment used to remove solar cell defects involves depositing a layer of organic ions HMS Victory in Portsmouth with HMS Queen Elizabeth behind. Courtesy of NMRN. that makes the surface too negatively charged. The team found that while the treatment is intended to improve energy-conversion efficiency during the fabrication process of perovskite solar cells, it also unintentionally creates a more electron-rich surface—a potential trap for energy-carrying electrons. This condition destabilizes the orderly arrangement of atoms, causing perovskite solar cells to become increasingly less efficient over time and ultimately making them unattractive for commercialization. With the new discovery, the team found a way to address the cells’ longterm degradation by pairing the positively charged ions with negatively charged ones for surface treatments. The switch enables the surface to be more electron-neutral and stable, while preserving the integrity of the defect-prevention surface treatments. Researchers tested the endurance of their solar cells in a lab under accelerated aging conditions and 24/7 illumination: The cells retained 87% of their original sunlight-to-electricity conversion performance for more than 2000 hours. In the control group, solar cells manufactured without the fix dropped to 65% of their original performance over the same time and conditions. ucla.edu. Thin-film perovskite solar cell produced with a manufacturing process tweak. Courtesy of UCLA. Researcher Nicola Symonds performs a tensile test on a wood sample. Courtesy of NMRN.
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 | A P R I L 2 0 2 2 6 MACHINE LEARNING | AI NEW METHOD INSPECTS 3D-PRINTED METAL PARTS Researchers from Nanyang Technological University, Singapore developed a fast and economical imaging technique that can examine the structure of 3D-printed metal parts. Most of these alloys comprise numerous microscopic crystals, which vary in size, shape, and atomic lattice orientation. By extracting this information, the alloy’s properties can be deduced. Traditionally, examining the microstructure of 3D-printed metal alloys involves time-consuming and costly measurements with scanning electron microscopes. The technique created by assistant professor Matteo Seita and his team offers the same quality of information within minutes by using a system comprising a flashlight, an optical camera, and a laptop computer that runs machine learning software designed by the team. First, the metal surface is treated with chemicals to expose the microstructure. Next, the sample is positioned to face the camera and numerous optical images are taken as the flashlight irradiates the metal from many directions. The software then examines the patterns generated by light reflected from the surface of diverse metal crystals and infers their orientation. The whole process takes about 15 minutes. The researchers then applied machine learning to program the software by inputting hundreds of these optical images. Ultimately, the software learned how to forecast the arrangement of crystals in the metal from the images, based on variances in how light disperses off the metal surface. It was then tested to develop a full crystal orientation map. Seita believes the new imaging technique could streamline the certification and quality assessment of 3D-printed metal parts. The technology could be especially useful in applications such as aerospace manufacturing and repair. www.ntu.edu.sg. PREDICTING DIRECTIONDEPENDENT PROPERTIES A machine learning algorithm developedat SandiaNational Laboratories could lead to a faster and more cost-efficient way to test bulk materials for use in automotive manufacturing, aerospace, and other industries. To screen materials such as sheet metal for formability, companies often use commercial simulation software calibrated to the results of various mechanical tests. However, these tests can take months to complete. Cer- tain high-fidelity computer simulations can assess formability in a few weeks, but companies need access to a supercomputer to run them. The Sandia team has shown machine learning can dramatically cut the time and resources required to calibrate commercial software because the algorithm does not need information from mechanical tests—or a supercomputer. The new algorithm is called MAD3, short for Material Data Driven Design. Researchers say the model has been trained to understand the relationship between crystallographic texture and anisotropic mechanical response. Working with The Ohio State University, Sandia trained the algorithm on the results of 54,000 simulatedmaterials tests using a feed-forward neural network. The Sandia team then presented the algorithm with 20,000 new microstructures to test its accuracy, comparing the algorithm’s calculations with data gathered from experiments and supercomputer-based simulations. “The algorithm is about 1000 times faster compared to high-fidelity simulations. We are actively working on improving the model by incorporating advanced features to capture the evolution of the anisotropy since that is necessary to accurately predict the fracture limits of the material,” says Sandia scientist Hojun Lim. sandia.gov. A low-cost imaging system that uses an optical camera and machine learning can analyze the properties of a 3D-printed metal alloy in 15 minutes. Researchers examine data generated by a newmachine learning algorithm.
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 | A P R I L 2 0 2 2 7 PROCESS TECHNOLOGY SELF-ASSEMBLING MATERIAL A new, scalable material that is stronger than steel and as light as plastic was developed by scientists at MIT, Cambridge, Mass., using a novel polymerization process. The new material is a 2D polymer that self-assembles into sheets, unlike all other polymers, which form one-dimensional, spaghetti-like chains. Until now, scientists believed it was impossible to induce polymers to form 2D sheets. Such a material could be used as a lightweight, durable coating for car parts or cell phones, or as a building material for bridges or other structures. The researchers have filed for two patents on the process they used to generate the material. For the monomer building blocks, they use melamine, which contains a ring of carbon and nitrogen atoms. Under the right conditions, these mon- omers can grow in two dimensions, tiny magnets embedded in it. The new “elastomagnetic” material takes advantage of a phase shift to greatly amplify the amount of energy the material can release or absorb. To do this, scientists must engineer a new structure at the molecular or even atomic level. However, this is challenging to do and even more difficult to do in a predictable way. According to the team, by using metamaterials, they were able to overcome those challenges. They not only made new materials but also developed the design algorithms that allow these materials to be programmed with specific responses, making them predictable. This research has applications in any scenario where either highforce impacts or ultrafast responses are needed. umass.edu. This new two-dimensional polymer self-assembles into sheets and could be used as a lightweight, durable coating for car parts or cell phones, or as a building material. Courtesy Christine Daniloff/MIT. forming disks. These disks stack on top of each other, held together by hydrogen bonds between the layers, which make the structure very stable and strong. Because the material self-assembles in solution, it can be made in large quantities by simply increasing the quantity of the starting materials. The researchers showed that they could coat surfaces with films of the material, which they call 2DPA-1. The researchers found that the new material’s elastic modulus is between four and six times greater than that of bulletproof glass. They also found that its yield strength is twice that of steel, even though the material has only about one-sixth the density. mit.edu. PROGRAMMABLE METAMATERIAL Using metamaterials, a research team from the University of Massachusetts Amherst engineered a new rubber-like solid substance that has surprising qualities—it’s programmable, and it can absorb and release very large quantities of energy. As such, this new material holds great promise for a very wide array of applications, from enabling robots to have more power without using additional energy, to new helmets and protective materials that can dissipate energy much more quickly. This new metamaterial combines an elastic, rubber-like substance with BRIEF Two cutting tool and gear tool providers, Star SU of Hoffman Estates, Ill., and Louis Bélet of Switzerland, formed a strategic partnership aimed to enhance each company’s product offerings and expand their combined reach within the Americas and Europe. star-su.com, www.louisbelet.ch. This elastic material is embedded with magnets whose poles are color-coded red and blue. Orienting the magnets in different directions changes the metamaterial’s response. Courtesy of UMass Amherst.
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 | A P R I L 2 0 2 2 8 METALS | POLYMERS | CERAMICS IMPROVING PROTECTIVE GEAR A versatile foam-like material was created by researchers from Johns Hopkins University, Baltimore, with applications in the development of protective gear and parts for the auto and aerospace industries. The new shock-absorbing material protects like a metal, but is lighter, stronger, and reusable. The research team was able to add strength while reducing weight with high energy-absorbing liquid crystal elastomers, which have mainly been used in actuators and robotics. During experiments to test the material’s ability to withstand impact, it held up against strikes from objects weighing about four to 15 pounds, coming at speeds of up to 22 mph. The tests were restrained to this speed due to limits of the testing machines, but the team is confident the padding could safely absorb even greater impacts. The team is exploring a collaboration with a helmet company to design, fabricate, and test next-generation helmets for athletes and the military. www.jhu.edu. The sti ness of the high-entropy Elinvar alloy remains invariant with temperature. Courtesy of City University of Hong Kong. SUPERELASTIC ALLOY A research team led by the City University of Hong Kong discovered a first-of-its-kind superelastic alloy that can retain its stiffness after being heated to 1000 K (~726.85°C) or above with nearly zero energy dissipation. The high-entropy alloy reveals the Elinvar effect, where the alloy firmly retains its elastic modulus over a very wide range of temperature changes. The team believes that the alloy can be applied in manufacturing high-precision devices for space missions. The mechanism behind the discovery is a special highly distorted lattice structure with a complex atomic-scale chemical composition. Because of the combination of unique structural features, the high-entropy Elinvar alloy has a very high energy barrier against dislocation movements. Consequently, The private equity firm Core Industrial Partners, Chicago, announces the acquisition of Haven Manufacturing by CGI Automated Manufacturing, also owned by Core. Haven specializes in components for medical devices and equipment, offering design assistance, prototyping, EDM, waterjet, laser etching, blasting, grinding and passivation, and CNC machining. havenmanufacturing.com. BRIEF it displays an impressive elastic strain limit and a nearly 100% energy storage capacity. The team also discovered that the alloy has an elastic limit of about 2% in bulk forms at room temperature, in sharp contrast to conventional crystalline alloys which have an elastic limit of less than 1%. The team developed three atomic structural models for the same alloy with different distributions of the element atoms and compared the properties. They patented the discovery based on this systematic investigation. Researchers say the alloy could be used for energy storage for subsequent energy conversion, since its elasticity doesn’t dissipate energy. The team envisions many applications for the alloy, particularly in aerospace engineering, in which devices and machinery are expected to undergo drastic temperature changes. www.cityu.edu.hk. Researchers studied the energy-absorbing capability of liquid crystal elastomers. Courtesy of Johns Hopkins 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 | A P R I L 2 0 2 2 9 ALUMINUM ALLOY BEHAVIOR Researchers at the Max Planck Institute for Iron Research (MPIE), Germany, are studying hydrogen in aluminum alloys at the atomic level in order to more efficiently prevent hydrogen embrittlement and found first approaches to hindering this effect. The MPIE researchers used 7xxx aluminum, a highstrength aluminum class that is the primary material of choice for structural components of airplanes. They charged their samples with hydrogen and performed tensile tests showing that the ductility decreases with increasing amounts of hydrogen. The fracture surface showed that cracks especially propagated along grain boundaries. Through cryo-transfer atom probe tomography, the scientists revealed that hydrogen gathered along those grain boundaries. They were able to show where hydrogen is located following its ingress during the material’s processing or in service. Essentially unpreventable, it is important to control its trapping. The researchers recommend different strategies to prevent hydrogen embrittlement, in particular using intermetallic particles that could trap hydrogen inside the bulk material. Additionally, control of the magnesium level at grain boundaries appears critical. “Magnesium paired with hydrogen at grain boundaries increases the embrittlement,” says lead researcher Huan Zhao. “At the same time, we must manipulate the correct size and volume fraction of particles in the bulk to trap hydrogen while maintaining the material’s strength.” The researchers are pursuing further studies on perfect particle distribution and eliminating magnesium decoration of grain boundaries to design advanced high strength, hydrogen-resistant aluminum alloys. www.mpie.de/2281/en. An aluminum-based alloy with zinc, magnesium, and copper studied after aging for 24 hours at 120°C, (a) and (b) electron imaging of an intergranular crack of the hydrogen-charged alloy subjected to tensile fracture. GB: grain boundary; GBPs: grain boundary precipitates. Courtesy of Nature. (a) (b)
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 | A P R I L 2 0 2 2 technique for detecting reduced efficiency in hydrogen fuel cells when enduring periods of excess or insufficient water. By using sensors that measure magnetic flux density, the amount of current generated can be monitored noninvasively, which can signal a problem. This work could lead to technology that can improve the reliability of fuel cells while also significantly reducing the carbon footprint of cars. The new detection system is based on the magnetic flux produced by electrical currents inside the fuel cell. When the system is operating correctly, its electrical currents generate a characteristic pattern of magnetic fields that can be detected by sensors. This allows failure states to be immediately registered after changes are noted in the magnetic flux. “Our research opens the possibility for automated control systems to be integrated into future fuel cells,” says lead researcher Yutaro Akimoto. This could pave the way for more efficient and practical zero-emission vehicles. www.tsukuba.ac.jp/en. SOUND MEASURES ELASTICITY Scientists from the U.K.’s University of Nottingham are measuring the speed of sound across a material’s surface todeterminemicroscopic elasticity. The innovation, referred to as spatially resolved acoustic spectroscopy (SRAS), uses high-frequency ultrasound to produce microscopic resolution images of the microstructure and maps the relationship between stresses and strains TESTING | CHARACTERIZATION FATIGUE CRACK MECHANISMS A team of researchers from Cornell University made advancements in better understanding how materials break. Using atomic modeling, the researchers identified the mechanism that causes fatigue cracks to grow—a defect in the structure that begins near the crack tip, moves away from it, then returns to a slightly different location. The finding could help engineers better anticipate a material’s behavior and design novel alloys that resist fatigue. The researchers set out to create a series of simulations of a structural alloy in a vacuum. Each simulation inserted a different artificial mechanism that might pro- voke the cracks to move forward, as they would in the real world. Some mechanisms included new sources of defects, irreversibility, and different forms of localized strain. Each time, the crack refused to budge. A fourth simulation succeeded in propagating the crack after the team realized the defects needed to interact more closely with the crack tip, such that the atomic bonds would break. While the modeling explains the mechanical mechanism at the root of fatigue cracks, there is still an open question about what role the environment plays in their growth. The group is now researching how dislocations can be steered to different locations and how loading can affect the process. This new understanding of prolonged fatigue can be applied to the design of materials, which has historically focused on how much loading a material can take before it fails. cornell.edu. FUEL CELL FAILURE Researchers from the University of Tsukuba, Japan, developed a new Magnetic Analysis Corp. (MAC), Elmsford, N.Y., acquired TacTic, a division of Laboratory Testing Inc. The purchase expands MAC’s line of NDT systems to include ultrasonic test systems that detect surface and subsurface defects in round tube, pipe, and bar. The systems enable metal producers to cost-effectively test small batches of material or frequent diameter size changes. mac-ndt.com. Ipsen, Cherry Valley, Ill., expanded its field service capabilities to include ultrasonic wall thickness testing for vacuum furnaces, which helps verify the integrity of the vacuum chamber and determine its remaining lifespan. The service is available anywhere in the U.S. on both Ipsen and non-Ipsen equipment. ipsenusa.com. BRIEFS This graphic shows the modeled atomic configuration at the tip of a fatigue crack that is on the verge of emitting dislocation defects. Courtesy of Cornell University. Ipsen vacuum chamber wall thickness testing.
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 | A P R I L 2 0 2 2 1 1 in the material—the elasticity matrix. These crystals are normally invisible to the naked eye, but by precisely measuring the speed of sound across the surface of these crystals, their orientation and the inherent elasticity of the material can be revealed. This technology is already starting to be used in fields such as aerospace to understand the performance of new materials and manufacturing processes. According to the researchers, the technique will launch a new field of research as it’s a completely new way to evaluate materials. It could be used to improve safety within systems like jet turbine blades or develop new designer alloys with tailored stiffness. For example, in medical implants, it is vital to match the stiffness of prosthetic devices to the properties of the human body to ensure harmonious operation. Along with the stiffness of the material, the elasticity matrix also provides insight intomany importantmaterial properties that are hard to measure directly, such as how the material responds to changes in temperature. This means the rapid measurement of the elasticity matrix can be used as a roadmap to discover next-generation materials with superior properties, making SRAS++ an essential tool in the development of new materials. www. nottingham.ac.uk. SRAS scan of titanium alloy. The color of the regions represents the speed of sound across the surface of that crystal. Courtesy of University of Nottingham.
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 | A P R I L 2 0 2 2 1 2 LIGHT TRANSFORMS MATERIALS Physics professor David Hsieh of Caltech, Pasadena, Calif., and his team recently used lasers to dramatically alter the properties of materials without producing any excess damaging heat. The researchers found an ideal material to demonstrate their method— a semiconductor called manganese phosphorus trisulphide, which naturally absorbs only a small amount of light over a broad range of infrared frequencies. The team used intense infrared laser pulses, each lasting about 10-13 seconds, to rapidly change the en- ergy of electrons inside the material. As a result, the material shifted from a highly opaque state to a highly transparent one for certain colors of light. The process also was found to be reversible. When the laser turns off, the material instantly goes back to its original state unscathed. The heat-free manipulation used in the new process is known as coherent optical engineering. The method works because the light alters the differences between the energy levels of electrons in the semiconductor without kicking the electrons themselves into different energy levels, which is what generates heat. The findings, Hsieh says,mean that other researchers can now potentially use light to artificially create materials, such as exotic quantummagnets, which are difficult or impossible to create naturally. “In principle, this method can change optical, magnetic, and many other properties of materials,” say the researchers. “This is an alternative way of doing materials science. Rather than making new materials to realize different properties, we can take just one material and ultimately give it a broad range of useful properties.” caltech.edu. MINERAL-BASED SEMICONDUCTORS A research team from Missouri University of Science and Technology introduced new potential for creating advanced semiconductor devices using a naturally occurring mineral. They demonstrated a new 2D material heterostructure that has many applications in compact sensors and detectors, optical communication, optical integrated circuits, and quantum computers. The team found that flakes of len- EMERGING TECHNOLOGY Researchers from Paragraf, U.K., and Queen Mary University of London successfully fabricated organic lightemitting diodes (OLEDs) with a monolayer graphene anode instead of using indium tin oxide (ITO). The team says the graphene OLEDs achieve identical performance to ITO OLEDs, which are widely used in mobile phone touchscreens and require the rare earth element indium. www.qmul.ac.uk. BRIEF genbachite, a mineral discovered a century ago in Switzerland, have strong anisotropic properties, meaning the flakes vary along axis lines depending on the orientation. The researchers say the characteristic could have implications for directional light-emitting devices, encrypted data transfer and signal processing, and polarization-sensitive photodetectors. They obtain ultrathin lengenbachite flakes—around 30 nanometers thick—by mechanically exfoliating the bulk mineral using Nitto PVC tape. Lengenbachite is composed of stacks of alternating, weakly bonded layers of four-atom-thick lead sulfide and five-atom-thick arsenic trisulfide. Notably, the researchers observed out-of-plane one-dimensional rippling structures along the lengenbachite flake surface. The ripples are caused by the periodic mechanical strain generated between the alternating atomic layers. With the help of several optical spectroscopic techniques, the researchers also found strong anisotropic optical properties in the flakes. mst.edu. Figure is a zoomed-in view of one crystal cluster of lengenbachite mineral rock with several blade-like crystal plates. A strong laser is seen illuminating a material in a low-temperature chamber. Courtesy of Caltech/David Hsieh Lab.
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 | A P R I L 2 0 2 2 1 3 FERROMAGNETIC GRAPHENE Surprising feats of physics can arise by stacking two sheets of the carbon nanomaterial graphene at a particular angle—an arrangement known as “magic-angle” graphene. Now, a research team from Brown University, Providence, R.I., discovered another mechanism to add to graphene’s impressive list. By inducing a phenomenon known as spin-orbit coupling, magic-angle graphene becomes a powerful ferromagnet. Previously, scientists found that when cooled to near absolute zero, magic-angle graphene transforms into a superconductor. “Magnetism and superconductivity are usually at opposite ends of the spectrum in condensed matter physics, and it’s rare for them to appear in the same material platform,” says lead researcher Jia Li. “Yet we’ve shown that we can create magnetism in a system that originally hosts superconductivity.” Li and his team interfaced magic-angle graphene with a block of tungsten diselenide, a material that has strong spin-orbit coupling. Aligning the stack precisely induces spin-orbit coupling in the graphene. The team found that the magnetic properties of magicangle graphene can be controlled with both external magnetic fields and electric fields, which would make this 2D system an ideal candidate for a magnetic memory device with flexible reading and writing options. Another potential application is in quantum computing, the researchers say. An interface between a ferromagnet and a superconductor has been proposed as a potential building block for quantum computers. The problem, however, is that such an interface is difficult to create because magnets are generally destructive to superconductivity. “We are working on using the atomic interface to stabilize superconductivity and ferromagnetism at the same time,” Li says. “The coexistence of these two phenomena is rare in physics, and it will certainly unlock more excitement.” brown.edu. NEUROMORPHIC SPINTRONICS An international team of collaborators from Tohoku University, Japan, and the University of Gothenburg, Sweden, achieved a breakthrough in neuromorphic spintronics resulting in new technology for brain-inspired comNANOTECHNOLOGY When layers of “magic-angle” graphene (bottom) encounter layers of certain transitions metals, it induces a phenomenon called spin-orbit coupling in the graphene layers. Courtesy of Li lab/Brown University. puting. Researchers demonstrated the first integration of a cognitive computing nano-element, the memristor, into another—a spintronic oscillator. Arrays of these memristor-controlled oscillators combine the non-volatile local storage of the memristor function with the microwave frequency computation of the nano-oscillator networks and can closely imitate the non-linear oscillatory neural networks of the human brain. Triangular holes make this material more likely to crack from le to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. In this award-winning image taken with a scanning electron microscope, the green spots are a surface coating developed to limit transmission of SARS-CoV-2. The flower was added. Ph.D. candidate Mohsen Hosseini and chemical engineering professor William Ducker, Virginia Tech, won the “most whimsical” category in the National Nanotechnology Coordinated Infrastructure image contest, held annually in celebration of National Nano Day. vt.edu. BRIEF Contest-winning image titled “Lotus on Anti-SARS-CoV-2 Coating.” Researchers examined the operation of a test device comprising one oscillator and one memristor. Resistance of the memristor changed with the voltage hysteresis applied to the top electrode. Upon voltage application to the electrode, an electric field was applied at the high-resistance state, compared to electric current flows for the low-resistance state. The effects of electric field and current on the oscillator differed from each other, offering various controls of oscillation and synchronization properties. www.tohoku.ac.jp/en, www.gu.se/en. Researchers are making progress on the development of energy-e icient artificial neurons capable of emulating braininspired processes.
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 | A P R I L 2 0 2 2 *Member of ASM International ARCHAEOMETALLURGICAL STUDY OF TWO ANCIENT COPPER COINS A scientific study of two copper coins from 1851 and 1853 reveals well-preserved symbols of a growing, newly independent Chile nation. A R C H A E O L O G I C A L M E T A L L U R G Y 1 Patricia Silvana Carrizo* Mendoza Regional Faculty, National Technological University, Argentina Peter Northover School of Archaeology, University of Oxford
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 | A P R I L 2 0 2 2 (a) (b) (c) (d) A set of coins created in the mid19th century for the Republic of Chile was studied to confirm its composition and manufacturing method. A one-cent coin from 1851 belongs to a private collector and a half-cent coin from 1853 was rescued from the Historical Fort May 25 Village archaeological site and is currently exhibited in the Narciso Sosa Morales Museum in Argentina. Through the study of currencies, the relationship between money and nations can be observed; they are a material testimony of the identity of a people, of an era, and of the monetary policies that have animated the economy. Engravers and craftsmen have shaped in metal many of the most significant characteristics of the history of a nation, as well as its artistic development. The rich iconographic heritage shows the historical symbols of these countries and gives a sense of identity. For example, the relatively new (at the time) nations of the Americas used new symbols such as erupting volcanoes, the sun, eagles, condors, Andean camelids, hands swearing on the constitution, and the figures of the Republic and Minerva as representations of freedom, among others. In the country of Chile, through the enactment of the law of January 9, 1851, the Chilean monetary system was transformed, going from reales and escudos to pesos and centavos, with the following equivalence 1 peso = 8 reales. The aforementioned law, in article 4 said, “There will be two kinds of copper coins, called cents and half a cent of refined copper without mixing any other metal.” The law of March 19, 1851 established that, “The copper coins will bear on the obverse the central star of the shield with the inscription: “Republic of Chile” and year of issue; and on the reverse the expression of its value, a bouquet of circular laurel, and the motto: “Economy is wealth.” Throughout the numismatic history of Chile different versions of the coat of arms have been used on coins. Initially, when Chile was a Spanish colony, the coats of arms of Spain were used. Later, when independence came, Chile’s coat of arms represented the Earth on a pillar. There were ducing tokens and coins in 1850 as a private enterprise, separate from, but in cooperation with the Royal Mint. In 1851 coins were minted for Chile. The same year copper plates were made for the Royal Mint to convert more simplified versions in which only the central flat star is shown, as in the case of the 1851 coin. The 1853 coin shows the coat with a five-pointed star with additional relief. CHILEAN AND ENGLISH MINTS To comply with this law, copper was commissioned from the Carlos Lambert smelter in Coquimbo (Chile). The plates produced were taken to Santiago where they were minted at the Casa de Moneda. Unfortunately, defects in the plates resulted in coins that were inconsistent in weight, which ranged between 8.388 and 9.400 g. This added to the technical deficiencies of the Mint in making of copper coins, being the first time such large quantities were produced, and led to the end of production of these coins in the country. The Birmingham Mint, a coining mint, originally known as Heaton’s Mint or Ralph Heaton & Son’s Mint, in Birmingham, England, started pro- Fig. 1 — The 1853 copper coin before (a and b) and after (c and d) electrolytic cleaning. Fig. 3 — Example of the 1853 half-cent coin in good condition. Fig. 2 — Obverse and reverse of 1851 historical coin, after electrolytic cleaning.
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 | A P R I L 2 0 2 2 mechanically removes some corrosion products from the metal surface. The results were achieved in 2 hours, a fraction of the typical time for metal cleaning, and with a degree of cleanliness that revealed all the details of the copper coin surface. Different results can be obtained depending on the intensity of the applied current, and can affect the rate of reduction of corrosion products to the metallic state and mechanical cleaning by the action of bubbles of hydrogen on the surface. In general, it is advisable not to work with very high currents due to the complexity of the chemical reactions that could affect the cleaning process[2]. Figures 1a and b show the state in which the 1853 copper coin was received and Figs. 1c and d show the coin after electrolytic cleaning. Figure 2 shows the 1851 coin after cleaning. The clean and polished coins show their origin, year of issue, monetary value, legend, and two laurels. The material is primarily copper with alloying elements that do not play a major role in the chemical composition (Table 1). The calamine formed (green) patina on its surface behaved as a protective barrier over time preventing corrosion; that is why the coin has an almost perfect state of preservation. METALLOGRAPHIC OBSERVATIONS OF THE 1853 HALF CENT COIN Figure 3 shows an example of the half cent 1853 Chilean coin as listed in the Standard Catalog of World Coins, also known as the Krause catalogs. The obverse side says “REPUBLICA DE CHILE” with the five-pointed star in relief, and year of minting 1853 between two points. The reverse side says “ECONOMIA ES RIQUEZA” (in English: economy is wealth), and the denomination in words is surrounded by laurels with a four-pointed star on the bottom. Note than in the 1853 coin from the study, the letter Q of “RIQUEZA” has a short outer tilde. The coin’s microstructure was investigated after etching with an alco- holic solution of 2% ferric chloride Fig. 4 — Micrograph of the 1853 historical copper coin showing corrosion from pitting. Reagent: Alcoholic solution of 2% ferric chloride (FeCl3). Magnification: 100x. TABLE 1 — COIN CHEMISTRY COMPOSITION Coin % Zn % Ni % Fe % Mn % Cu % Pb % Si % As % Bi 1853, Half cent 0.076 0.099 0.090 0.015 96.2 0.10 0.26 0.091 0.11 1851, One cent 0.063 0.069 0.062 0.016 80.0 0.066 0.48 0.10 0.079 Fig. 5 — Example of the 1851 one-cent coin in good condition. into pennies, halfpennies, farthings, half farthings, and quarter farthings. In 1852, the Mint won a contract to produce a new series of coins for France. In this, the Mint was a pioneer in the minting of bronze. In 1853, the Royal Mint was overwhelmed with the production of gold and silver coins. They even re-minted copper coins for Chile. The Birmingham Mint won its first contract to mint finished coins for Great Britain: 500 tons of copper, minted between August 1853 and August 1855, with another contract in 1856. During the peak of operation, the four presses of hit around 110,000 coins a day. CLEANING BY ELECTROLYTIC REDUCTION The two copper coins in this study were in good condition, having a well-preserved metallic core and an original surface that was covered with non-deforming corrosion products that could be reduced back to the metallic state. The researchers decided to use electrochemistry to clean the coins by electrolytic reduction[1]. This treatment creates a galvanic battery in which the metallic object to be treated acts as a cathode and a galvanized steel sheet (zinc) or an aluminum sheet acts as an anode, with a 1% M sodium hydroxide as the electrolyte. When the galvanic reaction takes place, the less noble metal, in this case the aluminum or zinc, loses electrons in favor of the most noble (copper), producing a reduction of some corrosion products back to the metallic state. At the same time, the reaction produces hydrogen, which when released in the form of bubbles
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 | A P R I L 2 0 2 2 variant, even rarer still, with the accent similar to that of the letter (Ñ). The 1851 coin from the study is quite worn due to the passage of time, but when looking at the letter Q, it is seen that the tilde crosses toward the inside of the letter[3] (Fig. 7). For the 1851 coin, the 2% alcoholic ferric chloride solution (FeCl3) was also used as the etching reagent, which shows a structure with a well-formed recrystallized grain matrix with straight twin lines, and very little porosity (Fig 8). There is no evidence of a second phase. X-ray fluorescence analysis of both coins confirms that only minor, trace-type alloy components are involved, with copper being the main component. Chemical composition and metallographic evidence indicate that the alloy is of a single phase and aligns with the aforementioned decree of January 9, 1851, which said coins were to be made of refined copper without mixing any other metal. Table 2 lists hardness values for both coins. MINTING PROCESS According to the manufacturing method used at that time, metal was melted in crucibles in a coal furnace, and poured into prepared rails to form solid ingots. Ingots that did not meet the required thickness were passed between two rollers that pressed the metal strip, stretching it to the desired thickness. When the rail hardened it was necessary to anneal it to relaminate it. If the rail was too long, it was cut into smaller pieces. After the rails were a thickness equal to the blanks, they were anneal- ed to make them more workable. To protect against oxidation from an- nealing, the rails were put in ovens in sealed boxes. Automated machines were used to drill the rail and obtain the blanks. These machines were manually fed, and the operator had to move the metal strip forward to the rhythm of the machine. The cut blanks then went through the press, creating a pre-listel, a rim or raised border, which, among other things, helped protect the engraved pattern. The press was formed phase. Some intracrystalline cracks have also occurred due to copper corrosion. METALLOGRAPHIC OBSERVATIONS OF THE 1851 CENT COIN Figure 5 shows an example of the one cent 1851 Chilean coin as listed in the Standard Catalog of World Coins. Similar to the 1853 coin, the obverse side says “REPUBLICA DE CHILE” with the five-pointed star in relief, and year of minting 1851 between two smaller stars. The reverse side says “ECONOMIA ES RIQUEZA,” the denomination in words is surrounded by laurels united with a double loop. There are variants regarding the shape of the letter Q in the word RIQUEZA (Fig. 6). The first type has the Q tilde outside of the letter (most common) and in the second type the tilde crosses the letter (rare). There is another (FeCl3). The 1853 coin shows a grain structure typical of hot working and annealed with some visible twin grains, variable grain size, and some porosity seen as dark holes due to corrosion (Fig. 4) There is no evidence of second TABLE 2 — COIN VICKERS MICROHARDNESS 1853 half-cent coin 1851 one-cent coin 1º 146 HV 138.7 HB 137 HV 130.15 HB 2º 132 HV 125.4 HB 109 HV 103.55 HB 3º 121 HV 115.0 HB 101 HV 95.95 HB AVERAGE 133 HV 126.36 HB 116 HV 109.88 HB Fig. 8 — Micrograph of the 1851 historical copper coin. Corrosion at the grain edge and detail of slight porosity. Reagent: Alcoholic solution of 2% ferric chloride (FeCl3). Magnification: 400x (a, b) and 100x (c). Fig. 6 — Three images of 1851 one-cent coins for the morphological comparison of the letter Q. Fig. 7 — Historical coin macroscopy of 1851 one-cent coin. (a) (b) (c)
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