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Texas A&M researchers design high-heat shape memory alloys for jet engines
October 16, 2018
Source: ASM International
Texas A&M University, College Station, announces that its researchers have developed high-temperature shape-memory alloys that may have the capability to operate in jet engines.
A jet engine is most fuel-efficient when the gap between the turbine blades and the case is minimized. However, this clearance has to have a fair margin to deal with peculiar operating conditions. HTSMAs incorporated into the turbine case could allow the maintenance of the minimum clearance across all flight regimes, thereby improving thrust specific fuel consumption.
Another important potential application of HTSMAs is the reduction of noise from airplanes as they come in to an airport. Planes with larger exhaust nozzles are quieter, but less efficient in the air. HTSMAs could automatically change the size of the core exhaust nozzle depending on whether the plane is in flight or is landing. Such a change, triggered by the temperatures associated with these modes of operation, could allow both more efficient operation while in the air and quieter conditions at touchdown.
Leader of the research is Dr. Ibrahim Karaman, Chevron Professor and head of the university’s Department of Materials Science and Engineering. Prof. Karaman and his colleagues decided to try increasing the operating temperatures of HTSMAs by applying principles from another new class of materials, high-entropy alloys, which are composed of four or more elements mixed together in roughly equal amounts. The team created materials composed of four or more elements known to form shape-memory alloys (nickel, titanium, hafnium, zirconium and palladium), but purposefully omitted gold or platinum.
“When we mixed these elements in equal proportions we found that the resulting materials could work at temperatures well over 500°C — one worked at 700°C — without gold or platinum. That’s a discovery,” said Prof. Karaman. “It was also unexpected because the literature suggested otherwise.”
How do the new materials work? Prof. Karaman said they have ideas on how they operate at such high temperatures, but do not have solid theories yet. To that end, future work includes trying to understand what is happening at the atomic scale by conducting computer simulations. The researchers also aim to explore ways to improve the materials’ properties even further. Prof. Karaman notes, however, that many other questions remain.
Industries and Applications | Aerospace and Defense
Materials Properties and Performance | Thermal Properties
Metals and Alloys | Shape Memory Alloys