Through-Focal HAADF-STEM Analysis of Dislocation Cores in a High-Entropy Alloy

High-entropy alloys (HEAs) are a new class of multi-component alloys that exhibit surprising characteristics, [1] including very large strain hardening rates, large fracture toughness at room temperature [2], and a strong temperature dependence of yield strength at or below room temperature. These properties are closely linked to nano-twinning and dislocation-mediated plasticity, yet little experimental work has explored dislocation dissociation, stacking fault energy, or core structures in these alloys [3]. In this study, an HEA, containing 5 elements (Cr, Co, Mn, Fe, and Ni) with equiatomic composition was deformed to a 5% plastic strain at room temperature [4]. Post-mortem 3mm disks were electro-polished using a solution consisting of 21% Perchloric acid and 79% Acetic acid and analyzed using a probe-corrected Titan 80-300kV along a [110] zone axis. Highly planar deformation was first observed by Otto et al. [5] and was active for this study as well. This planar deformation, involving dislocation arrays on {111} slip systems, may imply the existence of short-range order, low stacking fault energy (SFE), and/or supplementary displacements in the wake of dislocations.