Microstructural and mechanical characterization of an equiatomic YGdTbDyHo high entropy alloy with hexagonal close-packed structure

The microstructural and mechanical characterization of an equiatomic YGdTbDyHo high entropy alloy with hexagonal close-packed structure was performed. The phase state and chemical homogeneity of the solid solution were analysed with respect to crystal structure, phase stability, and oxide formation. It was found that Y-rich precipitates form at grain boundaries and that the alloy is prone to oxidation, leading to a homogeneous distribution of similar to 10 nm-sized oxides in the grain interiors. The plastic response at the sub-grain level was studied in terms of the activated slip systems, critical resolved shear stresses (CRSS), and strain hardening using micropillar compression tests. We observe plastic slip on the basal system, with a CRSS of 196 +/- 14.7 MPa. Particle strengthening and strength dependence on sample size are discussed on the basis of dislocation particle interaction and mechanical size effects. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.