Effects of cerium addition on microstructures and mechanical properties of CoCrNi medium entropy alloy films
Journal
Surface and Coatings Technology
Journal Volume
424
Date Issued
2021
Author(s)
Abstract
In this work, the effects of rare-earth element Ce addition on the microstructures and mechanical properties of (CoCrNi)100-xCex (x = 0, 1.05, 2.61, 4.2, 5.96) medium entropy alloy films (MEAFs) were investigated. A series of (CoCrNi)100-xCex MEAFs was fabricated by radio frequency magnetron co-sputtering. The XRD and TEM results showed that the structure transformed from FCC to FCC + HCP at x = 2.61. Also, as Ni precipitated with Ce to form CeNi5 HCP phase, the localized depletion of Ni would encourage CoCrNi to transform from FCC to HCP phase. With the further increase in Ce content, Ce4.2 film became mixed nanocrystalline and amorphous structures and Ce5.96 film was fully amorphous. The nanoindentation and micro-pillar compression tests were conducted to study the mechanical properties of films. Both the hardness and Young's modulus showed an initial increase, reached the maxima of ~10 GPa and ~200 GPa, respectively, at x = 1.05, and then decreased with the increasing Ce content. The trends of yield strength and ultimate strength versus Ce content were similar to hardness. These results demonstrated that small amounts of Ce addition could strengthen CoCrNi MEAFs due to solid solution strengthening. However, excessive Ce addition would reduce the grain size to below ~10 nm and weaken the CoCrNiCe system due to the inverse Hall-Petch effect. ? 2021 Elsevier B.V.
Subjects
Ce addition
Mechanical properties
Medium entropy alloy films
Microstructure
Rare-earth element
Compression testing
Elastic moduli
Entropy
Hardness
Iron
Lanthanum
Magnetron sputtering
Metallic films
Nanocrystals
Nickel
Rare earths
Alloy film
Ce contents
Mechanical
Medium entropy
Medium entropy alloy film
Microstructures and mechanical properties
Property
Radio-frequency magnetron co-sputtering
Rare-earths
Type
journal article