A team of researchers at NC State has developed a new alloy that is lightweight but has strength comparable to steel, making it the strongest known alloy with such a low density. The high strength-to-weight ratio of the alloy could lead to new applications in creating more fuel-efficient transportation.
The researchers include Carl Koch, a distinguished professor of materials science and engineering; Douglas Irving, associate professor of materials science and engineering; Khaled Youssef of Qatar University, and Alex Zaddach and Changning Niu, both doctoral students at NC State.
They started project about a year ago, working in part with funding from a National Science Foundation research grant given to them for high-entropy alloys.
“It is preliminary work, but it is very exciting, and it could be very important,” Koch said.
The aluminum alloy is a high-entropy alloy, which means it consists of five or more metals in approximately equal amounts. The alloy is a combination of aluminum, lithium, magnesium, titanium and scandium. The combination of these metals created a structure which is very strong, but has low density.
“We wanted to get a very low density alloy … this particular alloy is very hard and very light, with almost the same density of aluminum,” Koch said.
This alloy could have applications in creating more fuel-efficient transportation, as it could be used to construct more lightweight cars and airplanes. It may have other applications as well, but it is too early to know for certain, as the researchers have only done preliminary testing.
“There is always a high demand for materials that are both lightweight and strong,” Koch said.
Jake Barrett, a freshman studying chemical engineering, said an alloy such as this one could be really revolutionary, especially in transportation.
“I think that whenever you see new, lighter, stronger materials like this, leaps in technology can follow,” Barrett said.
To create the new material, the team first combined the metals using a ball mill, a piece of lab equipment used to combine crushed metal and other material. The metal was annealed, or heated and cooled slowly, which strengthened the metal.
The researchers chose the metals used in the alloy because they all had a similar atomic size and had low heats of mixing. These two qualities ensured that the metals could yield an alloy with a simple metallic structure, which is less brittle than other alloy structures.
Koch said these qualities are desirable when creating alloys.
“These metals can form a simple metallic structure, and these materials can have much better mechanical properties,” Koch said.
Due to both the process the team used and the properties of the materials, the resulting material has a very low density while also being very strong.
“It’s comparable to some ceramic solutions, but metallic material is advantageous because it is stronger,” Koch said.
Currently the team is working to try gain funding to work on the next step for the alloy: making it less expensive.
“One of the drawbacks is that it contains the element scandium, which is very expensive…so we want to look at varying the composition,” Koch said.
The alloy is composed of approximately 20 percent scandium, and the researchers are hoping to find a way to either eliminate the metal or reduce the amount used in the alloy.
“[The results] are very exciting,” Koch said. “But we need to do more research to really understand it.”
