Solidification Paths In The Ceramic System CaO-Al203-SIO2

Abstract:

Phase diagram models of system CaO-Al203-SIO2 sometimes may contain essential deformations, including the disruption of diagram topological structure, in accordance with the applied tasks solving. In particular, the immiscibility surface and four liquidus surfaces (3CaO*SiO2, 3CaO*2SiO2, 3CaO*Al2O3, CaO*6Al2O3) are absent in V. Danek's model . The model calculated by the thermodynamics software CaTCalc doesn't include three liquidus surfaces (3CaO*SiO2, 3CaO*2SiO2, 5CaO*3Al2O3). Our model, containing all geometrical elements (15 liquidus surfaces, immiscibility surface, 80 ruled surfaces, 16 horizontal complexes at the temperature of invariant points and 16 vertical planes of triangulation) and taking into consideration the peculiarities of liquidus surfaces structure, makes possible to consider all concentration fields and phase regions structures, to calculate the phases trajectories during solidification, to design the microstructures for any mass center at the given temperature and so on. The kinematical method of phase regions boundaries description on the experimental and calculation data is used for phase diagram model simulation. An initial data are defined by the coordinates of binary and ternary points, liquidus surfaces contours and curvatures. Considered system is characterized by 16 invariant transformations (nine – quasiperitectic ones, six – eutectic ones and one transition with the regrouping of two polymorphic modifications) and includes 33 two-phase and 46 three-phase regions. Obtained model may demonstrate the results of melt solidification within 117 two-dimensional, 163 one-dimensional and 45 zero-dimensional concentration fields. Compare: no more then 10 crystallization paths have been considered in the traditional tutorials and handbooks on materials science for the system СaО-Аl2О3-SiО2 . The computer model using allows to analyze the crystallization path for any concentration field. The crystallization stage also can be illustrated on the material balance diagrams: vertical - for the given composition, and horizontal – as isothermal states of isopleth.

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