Interfacial segregation of competitive impurities in embrittled and de-embrittled Fe-3%Ni
1997; Maney Publishing; Volume: 13; Issue: 11 Linguagem: Inglês
10.1179/mst.1997.13.11.877
ISSN1743-2847
AutoresA.V. Krajnikov, Matthias Militzer, J. Wieting,
Tópico(s)High Temperature Alloys and Creep
ResumoAbstractAbstractThe kinetics of surface segregation in embrittled and de-embrittled Fe-3 at.-%Ni-0.0ll at.-%Sb containing 20 at.-ppm S was studied by Auger electron spectroscopy at temperatures ranging from 550 to 630°C. In addition, information on the grain boundary segregation in the embrittled material has been obtained from analysing intercrystalline fracture surfaces. Grain boundary segregation is characterised by cosegregation of Sb and Ni, which is increasingly promoted as the grain boundary concentration of C decreases. On the surface of the embrittled material, segregation competition of S and Sb is observed. This is stimulated by Sb enrichment via grain boundaries. In the de-embrittled material, Sb surface segregation is inhibited so that S remains the dominant segregant. These differences in the kinetic behaviour are consistent with the demixing model of temper embrittlement. Further, the S-Sb segregation competition leads to an inhomogeneous surface chemistry; some of the individual facets are enriched with Sb, others with S. Thus, the S-Sb surface segregation competition is not only characterised by the presence of fast diffusion paths but also by anisotropy. The conditions for the segregation dominance are analysed using Guttmann's equilibrium segregation modelfor multicomponent systems.
Referência(s)