PSI - Issue 41

A.M. Ignatova et al. / Procedia Structural Integrity 41 (2022) 527–534 Ignatova A.M., Vereschagin V.I., Naimark O.B./ Structural Integrity Procedia 00 (2019) 000–000

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influence”; that is, a particular area of the melt proportional to the size of the spinel becomes a material for formation of a shell around the spinel by way of epitaxial growth.

Keywords: structure, image analysis, voronoi diagram, glass crystal material, pyroxene, crystallization

Introduction. Morphometrical parameters of structural components of glass-ceramic materials are crucial for achieving the desired properties (Ignatova A.M., Vereshchagin V.I. Model of stone casting material structure with increased wear resistance 2017), (Ignatova A.M., Vereshchagin V.I. Use of image analysis method in the study and statistical evaluation of particle parameters of the solid component of silicate and oxide-based welding aerosols, 2017). Experimental studies aimed at obtaining glass-ceramic materials with controlled structural parameters for the achievement of the desired level of mechanical and physical properties have shown that macrostructural parameters produce a significant influence on the properties: mutual location of structural components, degree of branching of the vitreous phase relative to the crystalline components, etc. (Ignatova A.M., Vereshchagin V.V. Prediction of properties of cast spinelide-pyroxene glass-ceramic materials through parameters of spherolite-mesh structure model, 2020). Macrostructural parameters of glass-ceramic materials depend on the crystallization conditions. The crystallization sequence is usually established post factum, during the study of an already solidified or crystallized material, based on known data such as Bowen's reaction series. With this approach, the minerals' crystallization sequence is determined by the sequence of reaction relationships between the minerals and the melt. Conclusions based on Bowen's reaction series are that after a certain period of growth of one crystalline component, physical and chemical parameters of the melt change, and the growth of another component begins. These conclusions are valid for equilibrium condition which does not occur during the process of production of glass-ceramic materials (Ivanov, 2008). In the process and synthetic melts, overcooling causes simultaneous crystallization of several mineral phases (Popov, 1984). Notably (Ivanov, 2006), in addition to idiomorphic and xenomorphic mineral surfaces, there are also induction (compromise) surfaces emerging through simultaneous growth of minerals. The simultaneous growth of mineral phases in the process of crystallization or solidification is accompanied by size dispersion of structural components and macrostructural zoning. Moreover, simultaneous crystallization of mineral phases having different growth rates cannot be described with Tamman's diagrams (Fedorov, 2008), firstly, because it disregards xenomorphism, and secondly, as noted in (Volarovich and Korchemkin, 1937), the crystallization process, specifically the concentration of crystallization centers in certain areas of the melt occurs not arbitrarily and spontaneously, but under the influence of solid and gaseous inclusions. In the absence of patterns that would help determine the morphometrical parameters of structural components of glass-ceramic materials, it is necessary to identify and study the peculiarities of the formation of the structure of glass ceramic materials in non-equilibrium conditions, taking into account the simultaneous growth of components in the presence of focal heterogeneity (inclusions) in the melt. A representative example of a melt with focal heterogeneity in the form of gaseous and solid inclusions (Gluck, 1973), characterized by the simultaneous growth of several mineral phases in non-equilibrium conditions, is the melt for obtaining cast glass-ceramic spinel-pyroxene materials; therefore, the purpose of this work is to study the peculiarities of formation of the structure of cast glass-ceramic spinel-pyroxene materials in the conditions of non equilibrium crystallization. Materials and methods of research. The research uses a melt of the following composition, weight %: SiO2 – 45; MgO – 15.5; CaO – 12.5; Al2O3 – 15.5; FeO – 6.5; Fe2O3 – 3.5; TiO2 – 1; Na2O+K2O – 3; CaF2 – 1.5; Cr2O3 – 1.5, and the material obtained through its crystallization and solidification. The melt has been obtained in a 200L crucible electric arc pilot melting facility with a graphite electrode (Ignatova et al., 2013). Two types of samples have been obtained; both were subjected to solidification in sand-clay molds (Popov et al. 2013), but at different process parameters of crystallization specified in Table 1. The structural parameters have been evaluated through petrographic analysis (optical microscope Nikon Eclipse E 600 POL) using image analysis (ImageJ-Fiji).