NANOSTRUCTURAL PROCESSES AT MELTING AND MOULDING OF SILUMINS

The existing theories of liquid state, crystallization and modifying don’t allow determining nanostructural physical and chemical mechanisms of melting and casting of silumins. To research thin structure of these processes, it is necessary to consider fusion as consisting of thermodynamic stable nanocrystals of phases and unstructured atomized zones. As a result of the conducted researches it is shown that melting and casting of silumins are complicated nanostructural processes. During melting and casting of hypoeutectic silumin the determining role is played by centers of crystallization of primary crystals of aluminum, aluminum nanocrystals, the dissolved and adsorbed hydrogen. The role of modifiers comes down to absorption of dissolved hydrogen and an intensification of process of coagulation of nanocrystals of aluminum in the centers of crystallization of primary crystals of aluminum. At processes of melting and casting of eutectic silumin the major role is played by the centers of crystallization of the eutectic crystals of aluminum, the dissolved and adsorbed hydrogen. The role of the modifying flux comes down to formation of a sodium emulsion on which there is an allocation of bubbles of hydrogen in case of the eutectic crystallization. It promotes a branching of crystals of aluminum and receipt of the modified eutectic microstructure. At processes of melting and casting of hypereutectic silumin the determining role is played by the centers of crystallization of primary crystals of silicon, silicon nanocrystals, dissolved and adsorbed oxygen. In this case the role of modifiers comes down to reduction of concentration of the adsorbed oxygen and an intensification of process of coagulation of nanocrystals of silicon in the centers of crystallization of primary crystals of silicon.

melting, casting, silumins, modifying, nanocrystals, centers of crystallization, nanostructural processes

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