Computational materials science experts at the US Department of Energy’s Ames Laboratory and their collaborators at Texas A&M and Tomsk State University in Russia have identified the source of and the way to tune the strength and ductility of high-entropy alloys (HEAs). The discovery may help the power-generation and aviation industries develop more efficient engines, reducing fuel consumption and carbon emissions.

The work is presented in a paper in Physical Review Letters.

High-entropy alloys are composed from four or more different elements, and often have many desirable properties—they are lightweight, strong, ductile, corrosion resistant and ideal for energy-generation applications in extreme environments, such as aviation.

However, because the elements that make up an alloy can vary, as well as their relative proportions, experimentally testing the sheer number of possible combinations and their properties is difficult and time-consuming.

The Ames Laboratory-led team used a quantum-mechanical modeling method to computationally discover and predict the atomic structure of a particularly promising HEA system, Fe_xMn_80−xCo₁₀Cr₁₀, and how transformations and defects in that structure result in a stronger, more ductile material.

When we can pinpoint these transformations and the effect they have on a material’s properties, we can predict the strength of it, and we can deliberately design strength and ductility into these very complex alloys.

—Ames Laboratory scientist Duane Johnson

These predictions were then confirmed experimentally, studying single-crystal samples with advanced electron microscopy, including selective-area and electron-backscattered diffraction. Notably, the method is applicable to any multi-element complex alloy.

Theory-guided computational design, Johnson said, holds great promise for optimizing the performance of these materials, making them stronger, more ductile, and in many cases, less expensive. These performance improvements could have big implications for applications in extreme environments, such as turbine engines for power-generation or aviation, which work more efficiently at higher temperatures.

Using this predictive method, we’ve been able to speed up our alloy development timeline by more than 50%, and demonstrate 10-20% higher operational temperatures.

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In the case of aviation, Johnson said, this could translate into hundreds of millions of dollars in cost savings, and a significant reduction in greenhouse emissions.

Resources

• P. Singh, S. Picak, A. Sharma, Y. I. Chumlyakov, R. Arroyave, I. Karaman, and Duane D. Johnson (2021) “Martensitic Transformation in Fe_xMn_80−xCo₁₀Cr₁₀ High-Entropy Alloy” Phys. Rev. Lett. 127, 115704 doi: 10.1103/PhysRevLett.127.115704