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

Abstract

The surface nano-crystallization of Ni2FeCoMo0.5V0.2 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 Ni2FeCoMo0.5V0.2 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.

Mechanical Properties of Metallic Materials Processed by Surface Severe Plastic Deformation

“…A great number of materials have been studied to demonstrate their treatability and to understand the mechanisms of microstructure evolution. These materials are classified in a large range including steels, 19,26,35,5977) copper and its alloys, 7880) aluminum and its alloys, 20,8185) magnesium and its alloys, 8688) titanium and its alloys, 25,34,8995) superalloys including IN718 alloy 96101) and GH4169 alloy, 102) uranium, 33) metal-based composite materials, 103) shape memory alloys NiTi, 104) metallic glasses, 105107) and medium entropy 108,109) as well as high entropy alloys. 110113) Note that for alloys based on same elements but with different atomic structures, for example steels (ferritic, austenitic or martensitic phases) and Ti alloys (¡, ¢ or ¢ metastable phases), their behavior while undergoing treatments could be very different.…”

Mechanical Properties and Deformation Mechanisms of Heterostructured High-Entropy and Medium-Entropy Alloys: A Review

“…The common methods for producing gradient materials include surface mechanical grinding treatment (SMGT) (Li et al, 2008), surface mechanical rolling treatment (SMRT) (Chen et al, 2020), surface mechanical attrition treatment (SMAT) (Yang et al, 2016), and rotationally accelerated shot peening (RASP) (Hasan et al, 2019;Liang et al, 2020). However, these surface treatment techniques produce only thin nanostructured surface layers with a depth of a few hundred micrometers (∼200 μm) along the thickness direction of materials.…”

Microstructure and Friction Properties of AlCrTiVNbx High-Entropy Alloys via Annealing Manufactured by Vacuum Arc Melting

“…For example, with Ni 45 (CoCrFe) 40 (AlTi) 15 surface nitriding [46], AlN, CrN and TiN phases are formed on the surface, effectively increasing the surface hardness of the alloy from 8.8 GPa to 14.9 GPa. Furthermore, the utilization of shot peening, laser remelting and various other technologies also have the potential to enhance the surface characteristics of HEAs [47,48].…”