Lattice Green's Function Method for Modeling Solid Solution High Entropy Alloys
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Date
2022-05
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The Ohio State University
Abstract
Solid solution high entropy alloys (HEAs) are a class of emerging materials composed of five or more elements in roughly equiatomic proportions that possess outstanding mechanical strength, high fracture toughness, and corrosion resistance at high temperatures. This makes them suitable candidates for use in extreme environments such as gas turbines where they could enable higher operating temperatures, allowing for greater combustion efficiency and reducing greenhouse gas emissions. HEAs have a near infinite compositional space and can be difficult and expensive to synthesize. This has limited their development and exploration to computationally costly atomistic simulations such as molecular dynamics. A lattice Green's function method is proposed to enable the rapid survey of the configurational and compositional space of solid solution HEAs. Lattice Green's functions allow for small atomic displacements of an array of atoms to be swiftly calculated through the application of forces. Custom nonlinear bonds are inserted into the model and iteratively relaxed to capture highly distorted regions of interest with greater accuracy while conserving computational resources. The configuration of "solutes" representing the different atomic components of an alloy can be permuted in a region of interest. Calculating changes in the energy landscape between configurations gives insight into the mechanical properties of a given composition. The work to shear a solute pair was found to be more dependent on atomic bond length and mismatch rather than stiffness. Insights such as this can be used to revise current theories of strengthening in solid solution HEAs. Further work will include modification to represent more relevant crystal structures and a full configurational survey to explore potential strengthening mechanisms. This work will speed the development of HEAs through the rapid assessment and identification of promising alloy compositions for further investigation by more accurate but computationally expensive atomistic simulations.