DOI: https://doi.org/10.32515/2664-262X.2019.1(32).79-86

Thermodynamic Processes During Crystallization and Formation of Segregation in High-strength Cast Iron Castings

Volodymyr Kropivnyy, Mykola Bosii, Olexandr Kuzyk, Olena Kropivnaуa

About the Authors

Volodymyr Kropivnyy, Professor, PhD in Technics (Candidate of Technics Sciences), Central Ukraіnian National Technical University, Kropyvnytskyi, Ukraine

Mykola Bosii, Sen. Lect., Central Ukraіnian National Technical University, Kropyvnytskyi, Ukraine

Olexandr Kuzyk, Associate Professor, PhD in Technics (Candidate of Technics Sciences), Central Ukraіnian National Technical University, Kropyvnytskyi, Ukraine

Olena Kropivnaуa, Associate Professor, PhD in Technics (Candidate of Technics Sciences), Central Ukraіnian National Technical University, Kropyvnytskyi, Ukraine

Abstract

The purpose of this work is to clarify the role of Gibbs energy accounting in crystallization and formation of liquidation in modified high-strength cast iron. The article presents the calculation of the interfacial distribution coefficients of silicon and manganese between austenite and the liquid phase of the alloy. The obtained dependence of the relationship between the distribution coefficient of the third element Xi and the temperature change of the austenitic-graphite eutectic for the systems Fe-C-Xi (Xi = Mn, Si). It is shown that silicon concentrates in austenite and liquor in the center of dendrites. In this case, manganese is concentrated in liquid and liquor to the periphery of the dendrite. The role of Gibbs energy change in the redistribution of silicon and manganese between a liquid and austenite is substantiated. It is revealed that element saturate the phase, whose Gibbs energy decreases more strongly from the impurity of the element. This leads to a decrease in the Gibbs energy of the entire system and determines the magnitude of the distribution coefficient of silicon and manganese between the phases. The nature of the Gibbs energy change is found to determine the direction of the redistribution of silicon and manganese between liquid and austenite. Silicon or manganese is also saturated with a phase whose Gibbs energy decreases more strongly from one of these elements. It has been shown that silicon concentrates in austenite and eliminates in the center of the dendrite while manganese concentrates in the liquid and eliminates the periphery of the dendrite.

Keywords

high-duty cast iron, spherical graphite, crystallization, segregation, phase, distribution

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