Chair of Materials, Technology and Eguipment of Foundry Saint-Petersburg State PolytechnicaL University (Saint-Petersburg, Russia):

Golod V. M., Cand. Eng., Prof. of the Chair, e-mail: cheshire@front.ru
Emelyanov K. I., Post-graduate

The article introduces the concept of the two-stage evolution of equiaxed dendritic crystallites during non-equilibrium solidification of multi-component iron-based alloys. The conditions for the formation of the initial dendritic structure with an uneven distribution of the ensemble of dendrite arm spacings are considered. It is shown that the subsequent diff usion coalescence of side branches leads to coarsening of dendrite arm spacings and the formation of local structural heterogeneity in the scale of individual dendrite and its nearest neighbors. Joint processes of heat exchange, the growth of crystallites (at mesoscale) and diffusion (at microscale) during the redistribution of alloy components between the phases and the formation of the dendritic structure are analyzed. The computation ratios to assess the initial dendrite arm spacing on the stage of free growth of dendritic branches and axes are shown. The system of equations and computational procedures to define by the Monte-Carlo method the secon dary dendrite arm spacing and their statistical distribution during evolution of the structure resulting from the coalescence of the side branches are presented. The contribution of different mechanisms of coalescence in the formation of local structural heterogeneity on the base of modeling were compared with experimental data. The deve loped method of numerical analysis of dendritic solidification can be used to improve estimates of the parameters of solidifi cation process as predictors structure in order to improve the adequacy of the forecast models.

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