Effective Surface Nano-Crystallization of Ni2FeCoMo0.5V0.2 Medium Entropy Alloy by Rotationally Accelerated Shot Peening (RASP)

Ningning Liang; Xiang Wang; Yang Cao; Yusheng Li; Yuntian Zhu; Yonghao Zhao

doi:10.3390/e22101074

Effective Surface Nano-Crystallization of Ni₂FeCoMo_0.5V_0.2 Medium Entropy Alloy by Rotationally Accelerated Shot Peening (RASP)

Entropy (Basel). 2020 Sep 24;22(10):1074. doi: 10.3390/e22101074.

Authors

Ningning Liang¹, Xiang Wang¹, Yang Cao¹, Yusheng Li¹, Yuntian Zhu^{1

2}, Yonghao Zhao¹

Affiliations

¹ School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
² Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong 999077, China.

Abstract

The surface nano-crystallization of Ni₂FeCoMo_0.5V_0.2 medium-entropy alloy was realized by rotationally accelerated shot peening (RASP). The average grain size at the surface layer is ~37 nm, and the nano-grained layer is as thin as ~20 μm. Transmission electron microscopy analysis revealed that deformation twinning and dislocation activities are responsible for the effective grain refinement of the high-entropy alloy. In order to reveal the effectiveness of surface nano-crystallization on the Ni₂FeCoMo_0.5V_0.2 medium-entropy alloy, a common model material, Ni, is used as a reference. Under the same shot peening condition, the surface layer of Ni could only be refined to an average grain size of ~234 nm. An ultrafine grained surface layer is less effective in absorbing strain energy than a nano-grain layer. Thus, grain refinement could be realized at a depth up to 70 μm in the Ni sample.

Keywords: deformation twinning; dislocation slip; medium entropy alloy; shot peening; surface nano-crystallization.