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

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.

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

  1. Todd Coolbaugh, Ph.D says:

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

  2. William Olenick says:

    Will it burn?

  3. Bob the Builder says:

    This is awesome! Definitely going to use this in my future constructions.

  4. Anthony Jackson says:

    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.

  5. Chris Hill says:

    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?

  6. ISAIAS HILERIO says:

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

  7. Marcus Aurellias says:

    Are there any pictures of this new alloy? I would like to see the finished product.

  8. yong zhang says:

    very nice work

  9. yong zhang says:

    Is there any ordered intermetallics like TiAl phase forming?

  10. Jagan says:

    Sir, can u tell the composition of the alloy, and the properties of the alloy

  11. brian littler says:

    Can it. Be used on AM machine in powder form?
    How much less expensive than Nitinol?

  12. Devin says:

    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).

  13. roosevelt rolland says:

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

  14. Dan says:

    Hi, how much does it weigh? Also, can this be aerodynamically sound under drone speed?

    Thanks

  15. Bill Kratzer says:

    curious as to the shock resistance or tolerance it can handle or transmits ?

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