Interfacial segregation at Cu-rich precipitates in a high-strength low-carbon steel studied on a sub-nanometer scale

The local composition of small, coherent Cu-rich precipitates with a metastable body-centered cubic structure in a ferritic α-Fe matrix of a high-strength low-carbon steel was studied by conventional atom-probe tomography. The average diameter, 〈 D〉, of the precipitates is 2.5 ± 0.3 nm at a number d...

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Bibliographic Details
Published in:Acta materialia 2006-02, Vol.54 (3), p.841-849
Main Authors: Isheim, Dieter, Gagliano, Michael S., Fine, Morris E., Seidman, David N.
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Ferritic steels
Gibbsian interfacial excess
Interface segregation
Metals. Metallurgy
Nanostructure
Precipitation hardening
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Summary:The local composition of small, coherent Cu-rich precipitates with a metastable body-centered cubic structure in a ferritic α-Fe matrix of a high-strength low-carbon steel was studied by conventional atom-probe tomography. The average diameter, 〈 D〉, of the precipitates is 2.5 ± 0.3 nm at a number density of (1.1 ± 0.3) × 10 24 m −3 after direct aging at 490 °C for 100 min to a near-peak hardness condition, yielding a value of 84 Rockwell G. Besides Cu, the precipitates contain 33 ± 1 at.% Fe and are enriched in Al (0.5 ± 0.1 at.%). Nickel and Mn are significantly segregated at the α-Fe matrix/precipitate heterophase interfaces. The Gibbsian interfacial excesses relative to Fe and Cu are 1.5 ± 0.4 atoms nm −2 for Ni and 1.0 ± 0.3 atoms nm −2 for Mn. The reduction of the interfacial free energy, calculated utilizing the Gibbs adsorption isotherm, is 16 mJ m −2 for Ni and 11 mJ m −2 for Mn.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2005.10.023