Next generation metal design, one atom at a time

How can metal fabrication studies lead to longer battery life and lighter cars? It all goes back to physics.

Researchers at the Pacific Northwest National Laboratory (PNNL) studied the effects of physical forces on minerals by directly observing changes at the atomic level in shear-deformed minerals.

During shear deformation a force is applied to change a metalForm also rearranges atoms, but not in the same way for every metal or alloy. The arrangement of the atoms can affect the properties of metals such as strength, formability, and conductivity, so a better understanding of how atoms move during cutting is an important part of the ongoing effort to design next-generation metals with specific atomization properties.

This visualization forms the basis for understanding how shear deformation creates the enhanced properties observed in metals produced using Shear Assisted Processing and Extrusion (ShAPE), a PNNL innovation in metalworking. During the production of ShAPE, the metal is processed using sliding style To produce high performance metal alloys for use in vehicles and other applications.

“If we understand what happens to metals at the atomic level during shear deformation, we can use this knowledge to improve a variety of other applications where metals are subjected to the same force, from increasing battery life to designing metals with properties specifications, such as lighters, stronger alloy for the sake of Wang, a PNNL lab colleague and leader of the research group studying shear-induced deformation forces, which he called the “most efficient compound.”

Atom puzzle

Physical strength is universal. The force that is intentionally applied during metal fabrication to form alloys is the same force that can damage the structure inside a battery and cause eventual failure. Researchers also know that shear deformation can radically change the microstructure of minerals in ways that they can material repair—Makes metal stronger, lighter and more flexible. But how this happened remains a mystery.

“If you photograph a runner on the track at the beginning and end of a run, you might think he doesn’t move at all,” explains Arun Devaraj, materials scientist at PNNL. “But if you photograph the runners walking down the track, you will know exactly how far they have traveled. Same thing here. If we understand exactly what happens to metals at the atomic level during shear deformation, we can apply this knowledge. strategically to design materials with specific properties “.

gold standard

To see how shear deformation rearranges metal atoms, the researchers used a special probe inside the a transmission electron microscope at PNNL, one of the few laboratories in the world that has this potential. The research team used a microscope to record how the rows of atoms move within the mineral during shear deformation. They started by looking at gold, the standard because it is easier to imagine at the atomic level.

When the researchers watched the gold go through the cutting process, they saw that the gold crystals broke into smaller grains. They observed that natural defects in the arrangement of gold atoms changed the way the atoms were moved by shear deformation. This is useful information because defects are common in metals during deformation, but they do not behave the same in all metals, which can directly affect the properties of the metal.

Defects in the crystals, grain size and microstructure of metals can affect the properties of metals, such as strength and toughness. This is why it is important to understand how shear deformation displaces metal atoms and affects the overall microstructure of a metal. metal, “said Shuang Li. The PNNL postdoc and first author of three studies share these findings.

Next, the research team looked into copper. They noted how shear deformation causes the formation of nanostructures, a structural feature that makes metals stronger. By looking at alloys of copper and niobium, they found that shear deformation affects atoms differently in the copper and niobium phases in the alloy. This is an insight that can show how alloys with certain properties are fabricated using shear deformation.

Information obtained from the study of how this force affects the metal during control Production process It can be translated and applied directly wherever the metal is subjected to the same physical force. For example, file atomic level PNNL visualization skills are also useful for understanding how PNNL materials are used difficult conditions (e.g. nuclear reactors) or clean energy applications (e.g. hydrogen transmission lines and storage tanks) will respond to external pressure. Longer batteries, lighter alloys for more efficient compounds, and custom designs for next-generation metals with improved strength and conductivity can all be made possible with a better understanding of the atomic physics of metal fabrication.

These studies appear in three research publications: In situ TEM monitoring of the shear-induced evolution of the microstructure in Cu-Nb alloys in the magazine script material, Nanotwin helps in the reverse formation of low angle grain boundaries under alternating shear loads in the magazine material of the document, And In situ monitoring of multiple deformations associated with the formation of sub-granulated edges in single copper crystals under bending from Material research letter.