Compositional and structural characterization of alloyed carbide by 3D atom probe and high-resolution TEM

ABSTRACT During tempering of solute supersaturated ferrous martensite, the face‐centered cubic MC‐type carbides (M is alloy elements) such as VC and NbC phases usually co‐precipitate on crystal defects such as dislocation and take on plate‐like morphology. Over‐tempering makes the plate‐like shape c...

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Bibliographic Details
Published in:Surface and interface analysis 2013-07, Vol.45 (7), p.1129-1134
Main Authors: Liu, Qingdong, Zhao, Shi-Jin
Format: Article
Language:English
Subjects:
3D atom probe
Alloy plating
alloyed carbide
Alloying elements
Carbides
Coarsening
compositional
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Diffusion
Exact sciences and technology
high-resolution TEM
Morphology
Nanostructure
Physics
precipitation reaction
structural characterization
Three dimensional
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Summary:ABSTRACT During tempering of solute supersaturated ferrous martensite, the face‐centered cubic MC‐type carbides (M is alloy elements) such as VC and NbC phases usually co‐precipitate on crystal defects such as dislocation and take on plate‐like morphology. Over‐tempering makes the plate‐like shape change to spherical shape because of Ostwald coarsening. The coarsening process strongly correlates to the diffusion behaviors of the carbon and carbide‐forming elements, and consequently inhomogeneous compositional and structural distribution in the carbides is formed. Three‐dimensional atom probe and high‐resolution transmission electron microscopy have been proved useful methods to characterize the composition, morphology and nanostructure of the carbides that precipitate in a quench‐tempered micro‐alloyed steel. Depending on the actual affinity with C and the diffusion behavior, Si and Al are rejected from the alloy carbide, whereas Mn, V and Nb are inhomogeneously enriched in it. The morphology and structure change with the compositional redistribution. During the coarsening process of the pre‐existing plate‐like carbide, transition carbide that is semi‐coherent with ferritic matrix is formed because of the disparity in diffusion ratio of different solutes. A core–shell complex nanostructure is consequently formed in the coarsening carbide, and the core and shell are identified as V8C7 enriched in Mn, Mo and Mo2C, respectively. Copyright © 2013 John Wiley & Sons, Ltd.
ISSN:0142-2421
1096-9918
DOI:10.1002/sia.5238