Researchers at the Department of Energy’s Oak Ridge National Laboratory and partners Lawrence Livermore National Laboratory and Wisconsin-based Eck Industries have developed aluminum alloys that are both easier to work with and more heat tolerant than existing products.
What may be more important, however, is that the alloys—which contain cerium—have the potential to jump-start the United States’ production of rare earth elements.
ORNL scientists Zach Sims, Michael McGuire and Orlando Rios, along with colleagues from Eck, LLNL and Ames Laboratory in Iowa, discuss the technical and economic possibilities for aluminum–cerium alloys in anarticle in JOM, a publication of the Minerals, Metals & Materials Society.
The team is working as part of the Critical Materials Institute, an Energy Innovation Hub created by the U.S. Department of Energy (DOE) and managed out of DOE’s Advanced Manufacturing Office. Based at Ames, the institute works to increase the availability of rare earth metals and other materials critical for U.S. energy security.
Rare earths are a group of elements critical to electronics, alternative energy and other modern technologies. Modern windmills and hybrid autos, for example, rely on strong permanent magnets made with the rare earth elements neodymium and dysprosium. Yet there is no production occurring in North America at this time.
One problem is that cerium accounts for up to half of the rare earth content of many rare earth ores, including those in the United States, and it has been difficult for rare earth producers to find a market for all of the cerium mined. The United States’ most common rare earth ore, in fact, contains three times more cerium than neodymium and 500 times more cerium than dysprosium.
Aluminum–cerium alloys promise to boost domestic rare earth mining by increasing the demand and, eventually, the value of cerium.
Karl A. Gschneidner and fellow scientists at the U.S. Department of Energy’s Ames Laboratory have created a new magnetic alloy that is an alternative to traditional rare-earth permanent magnets.
The new alloy—a potential replacement for high-performance permanent magnets found in automobile engines and wind turbines–eliminates the use of one of the scarcest and costliest rare earth elements, dysprosium, and instead uses cerium, the most abundant rare earth.
The result, an alloy of neodymium, iron and boron co-doped with cerium and cobalt, is a less expensive material with properties that are competitive with traditional sintered magnets containing dysprosium.
Experiments performed at Ames Laboratory by post-doctoral researcher Arjun Pathak, and Mahmud Khan (now at Miami University) demonstrated that the cerium-containing alloy’s intrinsic coercivity—the ability of a magnetic material to resist demagnetization—far exceeds that of dysprosium-containing magnets at high temperatures. The materials are at least 20 to 40 percent cheaper than the dysprosium-containing magnets.
“This is quite exciting result; we found that this material works better than anything out there at temperatures above 150° C,” said Gschneidner. “It’s an important consideration for high-temperature applications.”
Previous attempts to use cerium in rare-earth magnets failed because it reduces the Curie temperature—the temperature above which an alloy loses its permanent magnet properties. But the research team discovered that co-doping with cobalt allowed them to substitute cerium for dysprosium without losing desired magnetic properties.
Finding a comparable substitute material is key to reducing manufacturing reliance on dysprosium; the current demand for it far outpaces mining and recycling sources for it.