From Blacksmiths to Beamlines: 3D Atomic Revelations Transform Alloy Engineering

by Hiroshi Tanaka
Alloy Engineering

The groundbreaking research conducted by scientists at the University of California, Los Angeles (UCLA) has ushered in a new era in alloy engineering. This pioneering study marks the first-ever three-dimensional mapping of medium and high-entropy alloys, a development that has the potential to revolutionize the field by enhancing the toughness and flexibility of these materials.

Alloys, such as steel, which result from the combination of two or more metallic elements, play a fundamental role in modern life. They are essential for constructing buildings, transportation, appliances, and tools, including the very device you are using to access this information. Engineers have long grappled with a classic trade-off in materials: hard alloys tend to be brittle and prone to breaking under strain, while flexible ones are susceptible to denting.

Approximately two decades ago, the possibility of circumventing this trade-off emerged with the development of medium and high-entropy alloys. These novel materials offer a unique blend of hardness and flexibility not found in traditional alloys. The term “entropy” in their name denotes the level of disorder in the mixture of elements within these alloys.

In a groundbreaking feat, a research team led by UCLA has provided an unprecedented glimpse into the structure and characteristics of medium and high-entropy alloys. Leveraging advanced imaging techniques, they accomplished the first-ever three-dimensional mapping of the atomic coordinates within these alloys. Furthermore, they successfully correlated the mixture of elements with structural defects, a scientific breakthrough in material science.

Medium-entropy alloys combine three or four metals in roughly equal proportions, while high-entropy alloys combine five or more metals similarly. This is in stark contrast to conventional alloys, which are predominantly composed of one metal with other elements present in lower proportions. To illustrate the significance of the research, consider a blacksmith forging a sword. Surprisingly, small structural defects make metals and alloys tougher. As the blacksmith repeatedly heats a malleable metal bar until it glows and then rapidly cools it, structural defects accumulate, transforming the bar into a robust sword.

The research team focused on a particular type of structural defect called a twin boundary, known to be a crucial factor in the exceptional combination of toughness and flexibility exhibited by medium and high-entropy alloys. Twinning occurs when strain causes a section of a crystal matrix to bend diagonally while the surrounding atoms maintain their original arrangement, resulting in mirror images on either side of the boundary.

Creating these innovative alloys involved an extraordinary and rapid process reminiscent of the blacksmith’s craft. The scientists melted the metal at temperatures exceeding 2,000 degrees Fahrenheit for a fraction of a second and then rapidly cooled it. The objective was to solidify the alloy with the same diverse mixture of elements as in its liquid state. This process induced twin boundaries in six out of ten nanoparticles, with four of them each having a pair of twins.

Identifying these defects required the development of a specialized imaging technique called atomic electron tomography, which utilizes electrons due to the atomic-level details being much smaller than the wavelengths of visible light. The resulting data was mapped in three dimensions by capturing multiple images as the sample was rotated. Tuning atomic electron tomography to handle the complex mixtures of metals was a meticulous endeavor.

The researchers meticulously mapped each atom within the medium-entropy alloy nanoparticles. However, some of the metals in the high-entropy alloy were so similar in size that electron microscopy could not distinguish among them. Consequently, the map of these nanoparticles grouped the atoms into three categories.

The research findings revealed that the more atoms of different elements (or categories of elements) are mixed, the greater the likelihood that the alloy’s structure will change in a way that enhances its toughness and flexibility. These findings have the potential to inform the design of medium and high-entropy alloys, imparting added durability and unlocking properties not yet realized in traditional steel and alloys through the strategic engineering of element mixtures.

Studying defective materials typically necessitates the examination of each individual defect to understand its impact on the surrounding atoms. Atomic electron tomography is the only technique with the necessary resolution to achieve this. The ability to observe intricate atomic arrangements within such minuscule objects is truly remarkable.

To expand on their research, Miao and his colleagues are now developing a novel imaging method that combines atomic electron microscopy with a technique for identifying a sample’s composition based on emitted photons. This will enable the differentiation of metals with atoms of similar sizes. Additionally, they are working on ways to investigate bulk medium and high-entropy alloys and to unravel the fundamental relationships between their structures and properties.

This groundbreaking study was published in the prestigious journal Nature on December 20, 2023. It was made possible with support from the U.S. Department of Energy and conducted at Berkeley Lab’s Molecular Foundry, also sponsored by the DOE. The co-first authors of the study are Saman Moniri, a former UCLA postdoctoral scholar; Yao Yang, who earned a doctorate from UCLA in 2021; and Jun Ding of Xi’an Jiaotong University in China. Other co-authors include UCLA postdoctoral scholars Yuxuan Liao; former UCLA postdoctoral scholars Yakun Yuan, Jihan Zhou, Long Yang, and Fan Zhu; and Yonggang Yao and Liangbing Hu of the University of Maryland, College Park.

Frequently Asked Questions (FAQs) about Alloy Engineering

What is the significance of this UCLA research on alloys?

This UCLA research is groundbreaking as it marks the first-ever three-dimensional mapping of medium and high-entropy alloys, offering insights into their unique properties.

What are medium and high-entropy alloys?

Medium-entropy alloys combine three or four metals in roughly equal amounts, while high-entropy alloys combine five or more metals similarly, differing from conventional alloys.

How does this research impact alloy engineering?

By revealing the atomic structure and defects in these alloys, the research opens doors to designing tougher and more flexible alloys, potentially revolutionizing material engineering.

What is the role of twin boundaries in these alloys?

Twin boundaries are structural defects crucial to the exceptional combination of toughness and flexibility observed in medium and high-entropy alloys.

What is atomic electron tomography, and why is it significant?

Atomic electron tomography is an imaging technique used to identify defects at the atomic level, making it crucial for understanding how defects affect the surrounding atoms in materials.

What are the future directions of this research?

The researchers are developing new imaging methods to differentiate metals with similar-sized atoms and to explore fundamental relationships between alloy structures and properties.

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GrammarNerd December 20, 2023 - 11:02 pm

Great content but could use some spellcheck, folks! It’s “amazing” not “amaaazing.” _xD83D__xDE09_

EngineeringWizard December 21, 2023 - 1:53 am

Amaaazing! Alloy game-changer alert! This research opens doors to super-tough materials.

Reviewer123 December 21, 2023 - 7:12 am

woah, this is sum crazy alloy stuff, like sci-fi meets blacksmithing. tech is amazin’.

ScienceGeek27 December 21, 2023 - 11:32 am

3D atomic mapping – super cool! These alloys are the future, no doubt.

NewsJunkie December 21, 2023 - 1:45 pm

UCLA’s doin’ some heavy sciencing, & it’s like, alloys gone wild. Can’t wait to see where this leads!


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