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Y.V. Shan, J. Svoboda, F.D. Fischer, E. Kozeschnik:
"Determination of Substitutional-Interstitial Interaction from Chemical";
Advanced Materials Research, Vol 922 (2014), 922; 645 - 650.

The interaction between interstitially diffusing atoms and substitutional solute atoms, acting as
trapping sites, causes a non-negligible influence on the diffusion process itself and, consequently,
on many aspects of alloys, such as phase transformations, solubility, precipitation of carbides and
nitrides etc. The most important quantity in this treatment is the so-called trapping enthalpy (depth
of trap), which has been used in several approaches in literature over the last century. However, the
determination of the trapping enthalpy so far relies on approximations or assumptions on the one
hand (statistical approaches, quasi chemical approach) or is significantly limited due to high
complexity (ab initio approaches) on the other hand. The model introduced in this paper illustrates a
rigorous and efficient thermodynamically-based concept utilizing only the dependence of the
chemical potential of the interstitial component on the chemical composition of the alloy. Such a
dependency is available in a very precise form from CALPHAD thermodynamic databases. Using
the most recent databases available, the trapping enthalpies of carbon and nitrogen at various solute
atoms (trapping sites) are evaluated for austenitic and ferritic steels. Good agreement with previous
literature results is observed. The flexibility of the concept allows also for the treatment of trapping
in a multi-component system, where different types of solute atoms are responsible for different
depths of traps.

http://dx.doi.org/10.4028/AMR.922.645