A new family of smart materials offers could improve jet engine fuel efficiency and reduce noise over residential areas. The advance involves shape-memory alloys that can switch from one shape to another with specific triggers - in this case temperature.

Potential uses for these alloys involve extremely hot environments like a working jet engine, but until now, economical, high-temperature, shape-memory alloys (HTSMAs), have only functioned at temperatures up to about 400° C.

Materials scientists from Texas A&M and United Technologies Research Center discovered the materials while working on a NASA project investigating how to control the space between a jet engine’s turbine blades and case. These engines are most fuel-efficient when this gap is minimized, but the clearance must have a A vacuum arc melter fabricating nickel, titanium, hafnium, zirconium and palladium HTSMAs, a new smart material with the many potential applications. Source: Texas A&M University fair margin to function under specific operating conditions. HTSMAs incorporated into the turbine case could maintain the optimal clearance across all flight regimes, improving thrust-specific fuel consumption.

The HTSMAs could also be deployed to automatically change the size of the core exhaust nozzle depending on whether the plane is in flight or 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.

The researchers increased 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 materials were fabricated of four or more elements known to form shape-memory alloys, such as nickel, titanium, hafnium, zirconium and palladium.

The resulting materials performed well at temperatures in excess of 500° C without the inclusion of expensive gold or platinum. Computer simulations are expected to help researchers understand how the new materials operate at such elevated temperatures.

The study is published in Scripta Materialia.