Grain boundary segregation of elements of groups 14 and 15 and its consequences for intergranular cohesion of ferritic iron

Effect of Grain Size on Grain Boundary Segregation Thermodynamics of Phosphorus in Interstitial-Free and 2.25Cr-1Mo Steels

“…temperature of 520 °C and from 40.9 to 43.2 kJ/mol at the aging temperature of 560 °C. It has been reported that the free energy of segregation depends on the boundary characteristics and bulk composition and mainly varies in the range of 33 to 56 kJ/mol for phosphorus in Fe-based alloys [4,21,22]. Apparently, the present results agree well with the literature.…”

“…Clearly, the free energy of segregation increases evidently with increasing grain size at the same aging temperature. For the IF steel, when the grain size increases from 48 to 225 µm the free energy of segregation increases from to 42.8 kJ/mol at the aging temperature of 600 • C and from 39.6 to 43.8 kJ/mol at the aging temperature of 680 • C. For the 2.25Cr-1Mo steel, when the grain size augments from 55 to 179 µm, the free energy of segregation rises from 40.5 to 43.0 kJ/mol at the aging temperature of 520 • C and from 40.9 to 43.2 kJ/mol at the aging temperature of 560 • C. It has been reported that the free energy of segregation depends on the boundary characteristics and bulk composition and mainly varies in the range of 33 to 56 kJ/mol for phosphorus in Fe-based alloys [4,21,22]. Apparently, the present results agree well with the literature.…”

“…Lejcek et al [4][5][6][7][8] gathered numbers of experimental results from the literatures and analyzed in detail the thermodynamics of grain boundary segregation of several solute/impurity elements. A key discovery of their work is that a linear relationship between segregation entropies and enthalpies of solute atoms exists in multiple alloy systems.…”

Prediction of binary interaction coefficients in grain boundary segregation

“…We also suppose that X I 0 can possess discrete values, ie, N /6 where N = 4, 2, and 1. Thus, the values of X P 0 = 4/6, X Sb 0 = X Sn 0 = 2/6 are used in the prediction, which are close to the above experimental values (Table and Figure ). Using these values, together with the data for the solid solubility of solutes in α‐iron, we can determine the values of the Fowler binary interaction coefficient, α I ( Fe ) , which are listed in Table for substitutional segregants and in Table for interstitial segregants.…”

“…In the case of rather large atoms, which still segregate interstitially, only a single intrinsic interstitial position will be occupied per structural unit, so that X I 0 = 1/6. Experimentally, it was found that the values X P 0 = 2/3, X Sb 0 = 1/3, and X Sn 0 = 1/4 represent the best fit to explain the temperature dependence of grain boundary segregation in α‐Fe . Taking into account the above considerations together with these experimental data, we suppose that the saturation level of interstitial sites will decrease with increasing size of the segregant's atoms as shown in Figure .…”