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

Abstract

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 ∼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 <a> 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.