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

Dieter Isheim*, Michael S. Gagliano, Morris E. Fine, David N. Seidman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

229 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)841-849
Number of pages9
JournalActa Materialia
Volume54
Issue number3
DOIs
StatePublished - Feb 2006

Keywords

  • Ferritic steels
  • Gibbsian interfacial excess
  • Interface segregation
  • Nanostructure
  • Precipitation hardening

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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