Microstructure Refinement in the CoCrFeNiMn High Entropy Alloy under Plastic Straining

Abstract:

The effect of plastic deformation under various conditions of the equiatomic CoCrFeNiMn alloy with single face-centered cubic phase structure was studied. The alloy was rolled at room and cryogenic temperatures, and uniaxially compressed at room temperature and temperatures of 600-1100°C with different height reductions. In addition, multiaxial forging at 900-1000°C was performed. Scanning and transmission electron microscopy, including EBSD analysis, was widely employed to characterize microstructure of the deformed alloy. At room and cryogenic temperatures, mechanical twinning and shear banding plays play dominant role in microstructure evolution. Extensive refinement of the microstructure occurs as the result of rolling with reduction of 80%. During deformation at 600-1100°C, discontinuous dynamic recrystallization takes place. The recrystallized grains size and their volume fraction increases with increase of deformation temperature. Multiaxial forging at 900-1000°C was used to produce fully recrystallized structure with average grain size of 6.7 μm. The alloy in the initial condition had low yield strength of 160 Mpa but remarkable tensile ductility of 68%. Rolling substantial increases yield strength to 1120-1290 MPa, but results in loss of ductility. After multiaxial forging the alloy has balanced combination of properties – yield strength of 280 MPa and elongation of 56%.

• Periodical: Materials Science Forum (Volume 879)
• Pages: 1853-1858
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.1853
• Online since: November 2016
• Authors: Nikita Stepanov*, Dmitry Shaysultanov, Nikita Yurchenko, Margarita Klimova, Sergey Zherebtsov, Gennady Salishchev
• Keywords: Ductility, Dynamic Recrystallization, Forging, High Entropy Alloys (HEAs), Microstructure Refinement, Rolling, Strength, Twinning

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