How can learning about the manufacturing of metals result in lighter and longer-lasting batteries? It’s all physics, really. At the Pacific Northwest National Laboratory (PNNL), scientists are directly observing atomic-level changes in metals that are undergoing shear deformation in order to better understand how physical forces affect metals. Although not uniformly for each metal or alloy, the forces used during shear deformation to change a metal’s shape also rearrange its atoms. A better understanding of how atoms move during shear is a crucial component of ongoing efforts to custom design next-generation metals with specific properties from the atom up. Atomic arrangement can affect metal properties like strength, formability, and conductivity.
The improved characteristics seen in metals produced using Shear Assisted Processing and Extrusion (ShAPETM), a PNNL innovation in metals manufacturing, are the result of shear deformation, and these visualizations lay the groundwork for understanding how this occurs. Metals are processed using shear forces during the ShAPETM manufacturing process to create high-performance metal alloys for use in automobiles and other applications. Chongmin Wang, PNNL Laboratory fellow and head of the research team examining the forces of induced shear deformation, said: “If we understand what happens to metals on an atomic level during shear deformation, we can use that knowledge to improve countless other applications where metals experience those same forces—from improving battery life to designing metals with specific properties, like lighter, stronger alloys for more efficient vehicles.”
Physical forces exist everywhere. The same forces that are deliberately applied during the production of metals to create alloys can also damage internal battery structures, leading to eventual failure. Researchers have also discovered that shear deformation can fundamentally change the microstructure of metals, making them stronger, lighter, and more flexible. But it’s still unclear how that occurs. Arun Devaraj, a materials scientist at PNNL, said that if you took a picture of a track runner at the beginning and end of their run, you might think they didn’t move at all. “However, if you record the runner as they circle the track, you’ll be able to determine exactly how far they went. Here, it’s the same. We could strategically use this knowledge to create materials with particular properties if we knew exactly what happened to metals at the atomic level during shear deformation.
Researchers used a specialized probe inside a transmission electron microscope at PNNL, one of only a few labs in the world with this capability, to observe how shear deformation rearranges metal atoms. The research team observed the movement of individual rows of atoms within metals during shear deformation using a microscope. The standard because it is the simplest to visualize at the atomic level, they began by looking at gold. Researchers observed the shearing of gold and observed the fragmentation of gold crystals into smaller grains. They observed that shear deformation altered the movement of the gold atoms due to inherent flaws in the arrangement of the atoms. This information is helpful because, although defects are common in metals during deformation, their behavior varies across metals, which can have a direct impact on metal properties.
“A metal’s properties, such as strength and toughness, can be impacted by defects in the crystal, grain size, and microstructure of the metal. Shuang Li, PNNL postdoc and the first author on three studies that share these findings, said that it is crucial to comprehend how shear deformation moves metal atoms and influences the metal’s general microstructure. The research team then examined copper. They noticed how shear deformation produces nanotwins, which are structural traits that give metals more strength. They observed a copper and niobium alloy and discovered that the copper and niobium phases of the metal mixture have different effects on the atoms. This is an important realization that can guide the development of alloys with particular properties through shear deformation.
Anywhere that metal is exposed to the same physical forces, the knowledge gained from studying how these forces affect metals during controlled manufacturing processes can be directly translated and applied. The atomic-level visualization capability at PNNL, for instance, can be used to predict how materials used in harsh environments (such as nuclear reactors) or clean energy applications (such as hydrogen transmission lines and storage tanks) will react to outside stresses. By comprehending the atomic physics of metal manufacturing, it may be possible to create lighter alloys for more efficient vehicles, longer lasting batteries, and next-generation metals with improved strength and conductivity. The Laboratory Directed Research and Development program at PNNL, which is a part of the Solid Phase Processing Science Initiative, provided funding for this work. The Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility supported by the Department of Energy’s Office of Science, Biological and Environmental Research program and located at PNNL, was used for a portion of this study.