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R D K Misra 《Bulletin of Materials Science》1991,14(6):1309-1322
The influence of vanadium on grain boundary segregation of phosphorus has been studied in iron and iron-carbon alloys by means
of fracture experiments in a scanning Auger microprobe. The emphasis here is to study the effects of vanadium on the interaction
processes operative under circumstances when structure in the interior of the grain (in the present case carbide formation)
and grain boundary segregation form simultaneously. It is emphasized that to predict and analyse the behaviour of an alloy,
it is important to consider atomic interactions both at the grain boundaries and in the grain interior and that between the
constituents and the grain boundaries. The study suggests that the principal determining factor in the scavenging or retardation
of migration of phosphorus to the grain boundaries is whether vanadium is present in the combined form (say, carbide) or is
available in solid solution form. When vanadium is present in solid solution form, grain boundary segregation of phosphorus
is low because of the chemical interaction of vanadium and phosphorus. However, as carbon is increasingly introduced in the
alloy, vanadium now preferentially reacts with carbon in view of higher interaction for carbon as compared to phosphorus.
A consequence of this is the increase in the grain boundary concentration of phosphorus. In such a situation the presence
of excess carbon in addition to what is stoichiometrically required to precipitate the entire vanadium as vanadium carbides,
serves as a palliative with regard to the reduction in the intergranular concentration of phosphorus. This palliative behaviour
is explained in terms of the sitecompetition model. An effort is also made to examine the behaviour of segregating elements
in terms of whole range of probable interactions (both at the grain boundaries and in the grain interior) and chemical interaction
energies. 相似文献