Zhang Qian, Huang Ruirui, Zhang Xuan, Cao Tangqing, Xue Yunfei, Li Xiaoyan
Center for Advanced Mechanics and Materials, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.
Nano Lett. 2021 Apr 28;21(8):3671-3679. doi: 10.1021/acs.nanolett.1c00444. Epub 2021 Mar 23.
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 AlCrCoFeNi 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.
关于具有体心立方（BCC）相的单晶高熵合金（HEA）中的塑性变形机制的研究非常有限。我们在扫描电子显微镜内对具有三种取向（包括[100]、[110]和[111]）且直径为270 - 1583 nm的单晶BCC AlCrFeCoNi微柱/纳米柱进行了原位单轴压缩。实验结果表明，这些高熵合金微柱/纳米柱的屈服/流动应力存在显著的尺寸效应以及明显的应变硬化。特别是，具有〈100〉取向的高熵合金微柱/纳米柱表现出比BCC纯金属和AlCrCoFeNi对应物更高的应变硬化指数。透射电子显微镜观察和大规模原子模拟相结合表明，位错滑移、反应、缠结和积累以及固溶效应是导致观察到的屈服/流动应力尺寸效应和明显应变硬化的原因，但这些位错机制取决于纳米柱的取向。我们目前的研究揭示了BCC高熵合金单晶中的潜在变形机制。
