Chair of Physics and Chemistry of Cast Alloys and Processes, Saint-Petersburg State PolytechnicaL University (Saint-Petersburg, Russia):

Golod V. M., Cand. Eng., Prof.
Emelyanov K. I., Post-graduate
Orlova I. G., Post-graduate

E-mail (common): cheshire@front.ru

In the third part of the review it is noted that the number of publications devoted to the problem of heterogeneity of dendritic structure on the microscale, is very little. The coalescence models of dendritic branches are traditionally used to calculate the average value of the secondary dendrite spacing. The experimental data evaluates considerable scatter of dendrite arm spacing relative to the average values, with a coeffi cient of variation V = 0.2–0.25. Using a Monte Carlo simulation it was implemented the solution of formation of an array of data, according to the fi nal distribution of secondary dendrite arm spacing based on local system for the coalescence of neighboring secondary branches. This leads to the diff erent character of evolution with the activation of various competing mechanisms for individual local systems. The multiple implementations of this procedure for a large number of local systems leads to the formation of data that describe the resulting dendritic structure with its statistical parameters — the mean, standard deviation and probability density distribution (frequency) in the form of a histogram. The simulation results are used to assess the contribution of diff erent mechanisms of coalescence and are in good agreement with experimental data in predicting a broad spectrum of values of dendrite arm spacings. The radical increase in the accuracy of forecasting and analysis of the conditions of formation of the dendritic structure can be achieved through the development and application of computer models of nonequilibrium solidifi cation of ingots and castings that are based on the use of thermo-physical and physical-chemical characteristics of the alloys, determined by their thermodynamic modeling, taking into account the rate of convective heat transfer at the front formation of dendrites. It is advisable to unify the description of the experimental data on the basis of a polynomial form of the concentration factor of the regression equation.

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