Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 743, Issue -, Pages 361-371Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2018.11.073
Keywords
Non-equiatomic; High entropy alloy; Heterogeneous lamella structure; Geometrically necessary dislocations; Back stress
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A new method based on conventional thermomechanical processing is proposed for design of non-equiatomic FeNiCoAlTaB (NCATB) high entropy alloy (HEA) with multiscale heterogeneous lamella (HL) structures to achieve outstanding mechanical properties. Two kinds of microstructures are produced in this study: 1) specimens annealed at 1050 degrees C exhibit structure composed of fine grains and ultrafine grains, which exhibits a combination of high strength (UTS similar to 1050 MPa) and good ductility (elongation similar to 23%); and 2) specimens annealed at 1200 degrees C which exhibit structure composed of fine grains and coarse grains, which demonstrates excellent synergy of good strength (UTS similar to 890 MPa) and exceptional ductility (elongation similar to 43%). It has been shown that shear bands formed in the cold rolling step are responsible for the fine-grain area in both specimens. Additionally, precipitation of NiAl (B2) particles also affects the formation of HL structures due to Zener pinning effect. The back-stress strengthening mechanism, responsible for high strength and ductility, is verified through combined loading-unloading-reloading (LUR) cyclic tensile tests and electron backscatter diffraction (EBSD) based geometrically necessary dislocation (GND) density analysis.
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