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Research and Innovation

New ‘High-Entropy’ Alloy Is As Light As Aluminum, As Strong as Titanium Alloys

For Immediate Release

Researchers from North Carolina State University and Qatar University have developed a new “high-entropy” metal alloy that has a higher strength-to-weight ratio than any other existing metal material.

High-entropy alloys are materials that consist of five or more metals in approximately equal amounts. These alloys are currently the focus of significant attention in materials science and engineering because they can have desirable properties.

The NC State research team combined lithium, magnesium, titanium, aluminum and scandium to make a nanocrystalline high-entropy alloy that has low density, but very high strength.

“The density is comparable to aluminum, but it is stronger than titanium alloys,” says Dr. Carl Koch, Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State and senior author of a paper on the work. “It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material. The strength-to-weight ratio is comparable to some ceramics, but we think it’s tougher – less brittle – than ceramics.”

There are a wide range of uses for strong, lightweight materials, such as in vehicles or prosthetic devices.

“We still have a lot of research to do to fully characterize this material and explore the best processing methods for it,” Koch says.

At this point, the primary problem with the alloy is that it is made of 20 percent scandium, which is extremely expensive.

“One thing we’ll be looking at is whether scandium can be replaced or eliminated from the alloy,” Koch says.

The paper “A Novel Low Density, High Hardness, High-Entropy Alloy with Close-packed Single-phase Nanocrystalline Structures,” is published online in the open-access journal Materials Research Letters. Lead author of the paper is Dr. Khaled Youssef of Qatar University. Co-authors include Alexander Zaddach and Changning Niu, Ph.D. students at NC State; and Douglas Irving, an associate professor of material science and engineering at NC State. The work was supported in part by the National Science Foundation under grant number DMR-1104930.

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Note to Editors: The study abstract follows.

“A Novel Low Density, High Hardness, High-Entropy Alloy with Close-packed Single-phase Nanocrystalline Structures”

Authors: Khaled M. Youssef, Qatar University; Alexander J. Zaddach, Changning Niu, Douglas L. Irving, and Carl C. Koch, North Carolina State University

Published: online Dec. 9, Materials Research Letters

DOI: 10.1080/21663831.2014.985855

Abstract: A low density, nanocrystalline high-entropy alloy, Al20Li20Mg10Sc20Ti30 was produced by mechanical alloying. It formed a single-phase fcc structure during ball milling and transformed to single-phase hcp upon annealing. The alloy has an estimated strength-to-weight ratio that is significantly higher than other nanocrystalline alloys and is comparable to ceramics. High hardness is retained after annealing.

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  1. I never understand how can somebody make so much marketing about a poor materials like this…. They just measured the hardness – it is hard, but so are the ceramics… And from the hardness they compare it already to strength of titanium and steel that was measured in tension on standard samples…… It can be super super super hard, however it will be as brittle as glass, even when its metal. You will never be able to make any safe structure from this. Sorry to disappoint, but this is not a good piece of basic research.

  2. Have you tested the behavior of the new nano-alloy when it is exposed to extremes of pressure (both high and low)? I am also interested in how it behaves when bombarded by both high energy photons and particles.

  3. Say the material is 12″ in length & 12″ width..@ 1/8″ thickness…what is the breaking point when held at each end and bent in a N shape?..if held verticle and compressed @ what point does it bend and snap or just shatter?.

  4. Can this material be used on Air Plane and will there be a weight factor? That would cause a plane to operate unsafe.

  5. How about replacing scandium with vanadium? The melting point and boiling ppoints are both higher in vanadium but the only drawback is that vanadium’s density is 6.00(g cm) whereas scandium is 2.99(g cm).

  6. Normally an alloy HCP has low mechanical properties. If this alloy presents an structure lihe this. How is tis possible?

  7. Exciting!
    1. How long do you imagine before the lower cost non-scandium alloy will be available?

    2. What manufacturing processes are likely to produce the highest strength?

  8. Having worked in the F1 aerospace industries as a cnc miller, I wonder what it would be like to machine the material into specific parts? Very interesting times ahead.

  9. Have you characterized the corrosion properties of these alloys. I am at JCSU and am well equipped with electrochemistry, including EIS.

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