Atomic-scale characterization and modeling of 60 degrees dislocations in a high-entropy alloy

TM Smith and MS Hooshmand and SD Esser and F Otto and DW McComb and EP George and M Ghazisaeidi and MJ Mills, ACTA MATERIALIA, 110, 352-363 (2016).

DOI: 10.1016/j.actamat.2016.03.045

High-entropy alloys (HEAs) are an exciting new class of multi-component alloys some of which have unusual and remarkable properties. As of yet, little is understood about dislocation core structure and stacking fault energies in these alloys. For this study, a five-component, equiatomic alloy (CrMnFeCoNi) was deformed to 5% plastic strain at room temperature. Post-test observations using diffraction contrast scanning transmission electron microscopy (DC-STEM) analysis provide evidence for numerous planar slip bands composed of,1/2 < 110 > dislocations. More detailed analyses of dislocation separation distances were performed using high-order diffraction vector DC-STEM and atomic resolution high angle annular dark field (HAADF) STEM on 1/2 < 110 > dislocations in 60 degrees orientation. Large variations in dissociation distances are found, leading to the concept of a local stacking fault energy (SFE). This finding is supported through embedded-atom-method (EAM) calculations of a model, concentrated, three-element solid solution. For the first time, the Nye tensor and center of symmetry analysis were used collectively to accurately determine dissociation distance. Lastly, using high-resolution energy dispersive X-ray spectroscopy, no ordering or segregation was observed, indicating that this alloys is a true solid solution down to the atomic scale in the recrystallized and lightly deformed state. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Return to Publications page