To the theory of grain-boundary diffusion in nanostructured materials

Modeling of Growth and Formation of Pearlite Colonies for Simple Models of Alloys Iron-Carbon

“…Below we describe a model of formation of pearlite colonies near grain boundaries based on our model ( 8) and the following assumptions agreeing with experimental observations [9,10].…”

Experimental and theoretical study of the formation and growth of pearlite colonies in eutectoid steels

“…As mentioned, the colonies are usually formed just in this region, but until now there seem to be no microscopic explanations for that [1,2]. In the model suggested, we relate the formation of colonies to a great enhancement of carbon diffusion near grain boundaries discussed by a number of authors [17,18]. The results of our treatment show that in the simplest form presented this model can be applied only to the strongly deformed materials, such as those studied in Ref.…”

“…For the usual, relaxed grain boundaries such widths seem to be too high. However, in materials subjected to an intense plastic strain, the enhanced diffusion regions, according to theoretical estimates [18], should significantly broaden, and the inequality mentioned can be realized. In this connection, it can be interesting to compare our figures 18 and 19 to some experimental data about formation of pearlite colonies in strongly deformed steels obtained by Tushinsky et al [6] and presented in Figs.…”

“…Deviations from these "uniform" values of η and ζ (i. e., from their values of "zero-order" in non-uniformity) arise only due to the presence of last, gradient terms in Eqs. (18) which in the Ginzburg-Landau approach used are supposed to be small.…”

“…In particular, Bokshtein et al [17] found the carbon diffusivity near grain boundaries in ferrite at T = 550 o to exceed that within the grain by 3-4 orders of magnitude, and they observed a similar (though somewhat lower) enhancement of diffusion near grain boundaries of austenite. Authors of a recent theoretical work [18] discussed acceleration of diffusion near grain boundaries in strongly deformed materials; they concluded that the enhancement of diffusion in such materials should spread for the significant distances from grain boundaries. The enhanced concentration of carbon and carbides in vicinities of grain boundaries was noted by a number of authors [1,17].…”