A team of engineers led by Kiran Solanki, an associate professor of aerospace and mechanical engineering at Arizona State University, and Dr. Kristopher Darling at the Army Research Laboratory at Aberdeen Proving Ground, have developed a unique processing system for a divergent, stabilized bulk nanocrystalline copper-tantalum alloy that is able to retain high strength and enhanced creep resistance at high temperatures. The reported properties will change the theoretical understanding of how nanocrystalline metals deform at elevated temperatures. An article about the breakthrough, which has tremendous implications for the aerospace, naval, civilian infrastructure, and energy sectors, was published today in Nature Magazine.
The reduction of defects has been a key goal in the development of creep-resistant metals and alloys — materials that can resist deformity under the influences of stress and heat. For example, a turbine blade made of material that is not creep-resistant, will over time develop creep and lead to catastrophic failure.
Currently, nickel-based superalloys are used in turbine engines and can withstand temperatures up to 1,100 °C. But identifying new metallic materials that can function at even higher temperatures and stress has the potential to revolutionize turbine engine technology. The stabilized nanocrystalline alloy identified by Solanki, Darling and Professor Rajiv Mishra from the University of North Texas, represents a major step toward that goal.
In contrast, conventional “unstable nanocrystalline metals,” because of extreme microstructural instability, have never been considered a viable alternative to the single-crystal super alloys currently used. The creep properties of the reported findings show that stabilized nanocrystalline alloys are capable of achieving steady state creep rates 6-8 orders of magnitude lower than conventional nanocrystalline metals.
“Any nanograin materials that are developed as a result of this research will have an extraordinary impact on the future of all power generation-reliant industries,” says Solanki, a member of the faulty in the Ira A. Fulton Schools of Engineering School for Engineering of Matter, Transport and Energy. “Nanocrystalline alloys can now provide a level of creep resistance never before imagined, and can do so even at extremely high temperatures.”
“There have been few options when it comes to the design of creep-resistant materials for high temperature applications, in turn posing substantial challenges, especially in energy-related applications where generation and conversion processes often occur at high temperatures,” said Kyle Squires, Dean of the Fulton Schools. “Development of the nanocrystalline alloys by Prof. Solanki and his colleagues is a breakthrough and we anticipate major impacts across a vast array of disciplines. This work, while especially impactful, typifies that occurring in his lab.”
According to Solanki, the long-term vision is simple. “If you apply this technology to a high-melting point material, such as a nickel or cobalt base, it will increase the strength and provide creep resistance — and eventually improve turbine engine efficiency and reduce the carbon footprint.”