PSI - Issue 41

3

Ignatova A.M., Vereschagin V.I., Naimark O.B./ Structural Integrity Procedia 00 (2019) 000–000

A.M. Ignatova et al. / Procedia Structural Integrity 41 (2022) 527–534

529

Table 1. Process settings for obtaining cast glass-ceramic spinel-pyroxene materials.

Sample type

Process parameter

First crystallization mode

Second crystallization mode

Transformer voltage, V Transformer amperage, А

380

0–500 56–84 0–4600

Voltage at the furnace electrodes, V Amperage at the furnace electrodes, А

Melt temperature in the furnace during melting, °С: Start End Melt temperature after weir from the furnace into ladle, °С

1380 1600–1720 1600–1700

Temperature of the melt in the ladle during pouring into molds, °С

1500–1600

Temperature of isothermal holding of castings in the furnace, °С

900–950

Mold cooling rate immediately after pouring, °C/h

100

200

Cooling rate in the 1st stage of heat treatment, °C/h (4 hours)

30–45

90–110

Cooling rate in the 2nd stage of heat treatment, °C/h (12 hours)

15–25

35–55

Furnace temperature at the removal of castings, °С

50–80

The implemented production process provides solidification of the melt in contact with a casting mold and in contact with air; the structure image was captured sequentially from the edge in contact with air to the edge in contact with the mold. The following image processing methods were used: binarization and Voronoi diagrams. A Voronoi diagram breaks the plane into polyhedrons according to the points on the plane in a way that is the most rational relative to the points. The study assumes the phases with the most isomorphic growth boundaries as points for building the Voronoi diagrams. This approach ensures schematization and visual clarity in describing the material's structure (Fig. 1).

Fig. 1. An example of using the method of constructing Voronoi diagrams in the processing of microstructure images.

Results and discussion. Examination of the structure of the obtained materials by observation through an optical microscope has shown that the most isometric shape is typical of the structural components corresponding to the spinel structural formations (Fig. 2). Fig. 3 shows schematic depictions of sample structures obtained through the use of the method of building Voronoi diagrams obtained for the two types of crystallization, starting from the zone of contact with the air towards the zone of contact with the mold.