Deformation behavior of a model high entropy alloy from atomistic simulations

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 812; p. 141124
• Main Author: Farkas, Diana
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 22.04.2021; Elsevier BV
• Subjects: Atomistic simulation; Composition effects; Crystallography; Deformation mechanisms; Empirical analysis; Entropy; FCC metals; Grain boundaries; High entropy alloys; Mechanical behavior; Molecular dynamics; Plastic deformation; Simulation; Stacking faults; Tensile tests; High entropy alloys; Atomistic simulation; Mechanical behavior
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2021.141124

This paper reports atomistic simulation studies of deformation behavior in a model quinary high entropy FCC alloy. The simulations are based on empirical interatomic potentials and use massively parallel molecular dynamics techniques at the atomistic level to study the deformation mechanisms. The studies consider columnar polycrystalline samples containing pure tilt grain boundaries with random misorientations around the [110] crystallographic axis. Virtual tensile tests were performed and the material response analyzed using various techniques, focusing on the role that the local composition in the random alloy plays in the deformation mechanisms. Overall plastic response correlates well with the values of unstable stacking faults given by the potential, and it is therefore not meaningful to compare deformation response with that of any of the single components. The more meaningful comparison is with a corresponding “average atom” material that has the same average properties but no local randomness. The main effect of the random composition fluctuations is to make dislocation glide more difficult. These fluctuations also result in lower twin to stacking fault ratios in the deformed samples. The complex high entropy alloy presents a higher strength, and overall less plastic deformation for the same levels of stress. This is mostly driven by the fact that the dislocations emitted from the grain boundaries do not glide as easily in the random alloy as they do in the average atom material.