This project will identify and develop HEA s that have the key mechanical properties for use at elevated temperatures. Project personnel will make samples of the desired HEA compositions and perform compositional and microstructural analyses to characterize the structures of the developed HEAs. Researchers will perform conventional room-temperature and elevated-temperature uniaxial tensile and creep experiments. They will also use advanced characterization techniques, such as neutron and synchrotron diffraction, to determine structural changes of the new HEAs under applied stresses at high-temperatures. These advanced techniques will utilize in-situ testing of the mechanical behavior under uniaxial tension and compression or creep loading to identify deformation mechanisms under various stress loads at elevated temperatures.
High-entropy alloys (HEAs) developed with a novel alloy design approach using multiple principal elements in near equimolar ratios have emerged as candidate materials for high-temperature applications in excess of 800 degrees Celsius (ºC). The traditional alloy design method uses only one or two principal elements with small additions of other alloying elements. These applications include the advanced ultrasupercritical (AUSC) steam-based power generation cycle, which uses steam at temperatures and pressures well above its critical point. Operating a steam power plant at AUSC conditions (up to 760 ºC and 35 megapascals [MPa] pressure) results in fuel-to-electrical-power conversion efficiencies that are considerably higher than in conventional subcritical or supercritical steam power plants.
The Department of Energy (DOE) National Energy Technology Laboratory (NETL) is partnering with The University of Tennessee to perform fundamental studies on aluminum-chromium-copper-iron-manganese-nickel (AlXCrCuFeMnNi) HEAs for use in boilers and steam turbines at temperatures and pressures up to 760 ºC and 35 MPa, respectively, and higher. An integrated research approach that couples thermodynamic calculations and focused experiments will be used to identify HEAs that will outperform conventional alloys in these applications.
The expected results of the project will be one or more new HEA compositions that have the required mechanical properties (ductility and creep strength) to function in AUSC boilers up to 760 °C and a steam pressure of 35 MPa. The results will also demonstrate a computer-aided design approach for identifying and developing new types of alloys for advanced high-temperature fossil energy applications. The performance of the newly-designed HEAs should surpass that of previously-studied candidate HEA alloy systems (e.g., Al0.5CoCrCuFeNi), achieved by identifying compositions via computational thermodynamics that have phases providing better mechanical properties. The proposed research will also advance computational modeling used in the accelerated design of high-temperature alloys by enhancing the thermodynamic database for the AlXCrCuFeMnNi HEA system and developing quantitative creep modeling for designing a wide range of advanced precipitation-strengthened alloys.
Goals and Objectives
This project is to develop one or more new HEA compositions that have the required mechanical properties (ductility and creep strength) to function in AUSC boilers. The objectives of this project are to (1) perform fundamental studies on the AlXCrCuFeMnNi HEA system to determine its potential for use in AUSC boilers and steam turbines at 760 °C and 35 MPa and higher, and (2) develop an integrated approach to coupling thermodynamic calculations and focused experiments to identify HEAs that outperform conventional alloys. Phase compositions that might have microstructures with the best combined strength, ductility, and creep resistance will be identified utilizing computational thermodynamic calculations. The computational-thermodynamic results will be verified through focused lab-scale experiments. These experiments will be performed to confirm the phase compositions of HEAs, characterize the microstructure, and measure the key mechanical properties of the new HEAs.
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