Tensile deformation behavior and deformation twinning of an equimolar CoCrFeMnNi high-entropy alloy

The tensile deformation and strain hardening behaviors of an equimolar CoCrFeMnNi high-entropy alloy (HEA) were investigated and compared with low and medium entropy equiatomic alloys (LEA and MEA). The HEA had a lower yield strength than the MEA because the addition of Mn weakens solid solution har...

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Published inMaterials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 689; pp. 122 - 133
Main Authors Joo, S.-H., Kato, H., Jang, M.J., Moon, J., Tsai, C.W., Yeh, J.W., Kim, H.S.
Format Journal Article
LanguageEnglish
Published Lausanne Elsevier B.V 24.03.2017
Elsevier BV
Subjects
Crystal defects
Cube texture
Deformation
Deformation effects
Diffraction
Dislocations
EBSD
Electron backscatter diffraction
Elongation
Entropy
FCC metals
High entropy alloys
High-entropy alloy
Mechanical properties
Solution strengthening
Stacking fault
Strain hardening
Studies
Substructures
Tensile deformation
Twinning
TWIP steels
Stacking fault
Twinning
Strain hardening
EBSD
High-entropy alloy
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Summary:The tensile deformation and strain hardening behaviors of an equimolar CoCrFeMnNi high-entropy alloy (HEA) were investigated and compared with low and medium entropy equiatomic alloys (LEA and MEA). The HEA had a lower yield strength than the MEA because the addition of Mn weakens solid solution hardening in the HEA. However, deformation twinning induced the multiple stage strain hardening behavior of the HEA and enhanced strength and elongation. Using tensile-interrupted electron backscatter diffraction analysis, geometrically necessary dislocations were observed as plume-shaped features in grain interior, and a considerable texture was characterized, which is typical of face centered cubic metals. Moreover, the relationship between favorably oriented grains and twinning in the HEA bore a clear resemblance to the same tendency in TWIP steels. The thickness of the twin bundles was less than 100nm. A high density of stacking defects was found in the nanotwins. Nano twinning and stacking faults were found to contribute to the remarkable mechanical properties. Deformation induced twinning not only demonstrated the dynamic Hall-Petch effect but also changed dislocation cell substructures into microband structures.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2017.02.043