Deformation Mechanisms and Remarkable Strain Hardening in Single-Crystalline High-Entropy-Alloy Micropillars/Nanopillars.
There have been very limited studies on plastic deformation mechanisms in single-crystalline high-entropy alloys (HEAs) with body-centered cubic (BCC) phases. We performed in situ uniaxial compression on single-crystalline BCC AlCrFeCoNi micropillars/nanopillars with three orientations (including [100], [110], and [111]) and diameters of 270-1583 nm, inside a scanning electron microscope. The experimental results showed the significant size effects on yield/flow stress and the remarkable strain hardening in these HEA micropillars/nanopillars. Especially, HEA micropillars/nanopillars with ⟨100⟩ orientation exhibited higher strain hardening exponents than BCC pure metals and Al0.7CrCoFeNi counterparts. A combination of transmission electron microscopy observations and large-scale atomistic simulations revealed that dislocation slip, reaction, tangling and accumulation, and solid solution effects are responsible for the observed size effects on yield/flow stress and remarkable strain hardening, but these dislocation mechanisms are dependent on nanopillar orientation. Our present study sheds light on the underlying deformation mechanisms in BCC HEA single crystals.
['Zhang|Qian|Q|http://orcid.org/0000-0002-4541-4798', 'Huang|Ruirui|R|', 'Zhang|Xuan|X|', 'Cao|Tangqing|T|', 'Xue|Yunfei|Y|', 'Li|Xiaoyan|X|http://orcid.org/0000-0002-2953-9267']
strain hardening orientation size effect dislocation slip solid solution high entropy alloys