posted on 2021-03-23, 21:14authored byQian Zhang, Ruirui Huang, Xuan Zhang, Tangqing Cao, Yunfei Xue, Xiaoyan Li
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.