“What we’re seeing is a revolutionary property arising in a class of materials that we never thought was possible,” said Dr. Kristopher A. Darling, a materials scientist with the laboratory’s Lightweight and Specialty Metals Branch.
Darling and his team of collaborators published startling new findings in the September issue of the scientific journal Nature that, he believes, could lead to many new materials applications, including inside turbine engines, where temperatures can soar to more than 2,500 degrees Fahrenheit.
In the Nature paper, “Extreme creep resistance in a microstructurally stable nanocrystalline alloy,” published Wednesday, Sept. 14, Darling outlines how his team stabilized a copper alloy microstructure and found it to be strong at very high temperatures.
The Department of Defense depends on jet turbine engines that require just this combination of high-structural strength coupled with high thermal stability, though the material is copper, not a material typically used in engines.
“But what it demonstrates is that these types of microstructures are capable of achieving properties that are extraordinarily high in comparison to what you would normally see in a conventional type of material,” Darling said.
The team hopes to recreate the combination of properties within other types of materials like nickel, cobalt or tantalum, which would have the potential to revolutionize engine technology.
Darling said the findings are all about the “creep response” of the paper’s title, which refers to how materials deform under continuous stress at elevated temperatures.
“We’re seeing orders of magnitude improvements in the creep response,” he said. “There is a six to eight orders of magnitude increase in creep response relative to what conventional nanocrystal materials can do.”
According to Darling, results from the preliminary tests of the material left the scientists scratching their heads. So they reached out to colleagues at the University of North Texas and Arizona State University to confirm what they were observing was correct.
“A lot of times unique discoveries are made by accident or by sheer luck, and this was one of those cases where we started to probe the material and we didn’t see the response that we were expecting,” Darling remembered.
Scientists at these institutions were just as baffled.
“They didn’t believe it either,” he said. “They said there’s no way that this could be possible. They began to test the samples themselves, and then they were amazed. From there, all the excitement grew … Ultimately it led to writing this paper.”
Nanotechnology research in metals is a relatively young field, he said. Just a couple of decades ago, researchers were just learning how to synthesize nanomaterials in bulk form and just beginning to understand their fundamental properties.
Darling has been studying this material for about five years. He started working at the laboratory after earning his doctoral degree from North Carolina State University in 2009.