Grain-Size Effects on the Deformation in Nanocrystalline Multi-Principal Element Alloy

19 Pages Posted: 4 Mar 2021

See all articles by Ankit Roy

Ankit Roy

Lehigh University - Department of Mechanical Engineering and Mechanics

Ram Devanathan

Pacific Northwest National Laboratory

Duane D. Johnson

Iowa State University - Ames Laboratory, U.S. Department of Energy

Ganesh Balasubramanian

Lehigh University - Department of Mechanical Engineering and Mechanics

Abstract

Multi-principal element alloys (MPEAs) continue to garner interest due to their remarkable mechanical properties, especially at elevated temperatures. Here, we examine a representative nanocrystalline refractory MPEA and identify a crossover from a Hall-Petch to inverse-Hall-Petch relation. While the considered MPEA predominantly assumes a single-phase BCC lattice, the presence of grain boundaries imparts amorphous phase distributions that increase with decreasing grain size (i.e., increasing grain boundary volume fraction). Using molecular dynamics simulations, we find that the yield strength of the MPEA increases with decreasing average grain size, but below a critical grain size < 23.2 nm the yield strength decreases. This change in the deformation behavior is driven by the transition from dislocation slip to grain-boundary slip as the predominant mechanism. Our results reveal that the change from Hall-Petch to inverse-Hall-Petch regime is correlated to dislocation stacking at the grain boundary when dislocation density reaches a maximum.

Keywords: multi-principal element alloys, nanocrystalline grains, molecular dynamics, Hall- Petch relation, dislocation slip

Suggested Citation

Roy, Ankit and Devanathan, Ram and Johnson, Duane D. and Balasubramanian, Ganesh, Grain-Size Effects on the Deformation in Nanocrystalline Multi-Principal Element Alloy. Available at SSRN: https://ssrn.com/abstract=3797413 or http://dx.doi.org/10.2139/ssrn.3797413

Ankit Roy

Lehigh University - Department of Mechanical Engineering and Mechanics

United States

Ram Devanathan

Pacific Northwest National Laboratory ( email )

901 D Street
370 L'Enfant Promenade, S.W.
Washington, DC 20024-2115
United States

Duane D. Johnson

Iowa State University - Ames Laboratory, U.S. Department of Energy ( email )

Ames, IA 50011-2063
United States

Ganesh Balasubramanian (Contact Author)

Lehigh University - Department of Mechanical Engineering and Mechanics ( email )

United States

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