New 'high-entropy' alloy is as light as aluminum, as strong as titanium alloys

December 10, 2014 by Matt Shipman, North Carolina State University

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 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 , but very high strength.

"The is comparable to aluminum, but it is stronger than titanium ," 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 , 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.

Explore further: New technique creates stronger, lightweight magnesium alloys

More information: 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. DOI: 10.1080/21663831.2014.985855

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24volts
3.8 / 5 (4) Dec 10, 2014
They need to start all over on this one. Lithium, titanium, and scandium are all expensive metals. It would have to be some really serious need for that particular alloy to make it worthwhile at all. I bet making this alloy would be really expensive too.
Urgelt
5 / 5 (3) Dec 12, 2014
24volts wrote, "They need to start all over on this one. Lithium, titanium, and scandium are all expensive metals. It would have to be some really serious need for that particular alloy to make it worthwhile at all. I bet making this alloy would be really expensive too."

I'm sure that's all completely obvious to the researchers, 24volts. (To us, too.)

It's just basic research, not a product announcement.
gkam
3 / 5 (4) Dec 12, 2014
No matter how much it costs, we will buy it for the military.
24volts
not rated yet Dec 12, 2014
24volts wrote, "They need to start all over on this one. Lithium, titanium, and scandium are all expensive metals. It would have to be some really serious need for that particular alloy to make it worthwhile at all. I bet making this alloy would be really expensive too."

I'm sure that's all completely obvious to the researchers, 24volts. (To us, too.)

It's just basic research, not a product announcement.


Yes I know but those metals would have to be smelted in an airless atmosphere and the melting temps are pretty far apart on them which makes for an interesting mix
Modernmystic
1 / 5 (1) Dec 12, 2014
If we were allowed to mine for rare Earth's in the US without some of the more histrionic regulations in existence we'd have no problem getting the scandium for this....not to mention thorium and a host of other rare Earths currently only being mined in China without ANY regulation (which is creating a hell of an environmental mess over there)

In short, some regulation makes good sense, but just because the EPA says something is necessary doesn't mean it's a holy nugget of sacrosanct necessity from the mother Gaia...
gkam
3 / 5 (4) Dec 12, 2014
We've used electron beams for vacuum melting for decades. There used to be at least two facilities in the SF Bay Area.
24volts
5 / 5 (2) Dec 12, 2014
We've used electron beams for vacuum melting for decades. There used to be at least two facilities in the SF Bay Area.


Yes, we have and the stuff made that way is extremely expensive and only used for 'have to have it' type requirements. I can see it being used maybe for the prosthetics like suggested in the article because people are already used to paying 10x what that stuff should cost simply because it has a 'medical' tag on it but in a vehicle? Moon or Mars buggy maybe?

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