Young’s modulus of glass ceramics obtained from igneous rock: impulse excitation x instrumented indentation

Reference Presenter Authors
10-061 Angelo Pradella Titton Titton, A.P.(Universidade de Caxias do Sul); Cruz, R.C.(Universidade de Caxias do Sul); Glassy materials can be produced by the solidification of molten igneous rocks. When subjected to controlled heat treatments, these glasses undergo partial to complete crystallization and develop a characteristic microstructure. Partially devitrified materials (glass-ceramics) exhibit interesting mechanical properties. In this work, glass-ceramics were prepared from a basalt containing ~50 wt% SiO2 (basic igneous rock from the Serra Geral Formation, RS, Brazil). Melting was carried out at 1550 °C and the crystallization temperatures of the base glass were determined by thermal analyses, both on heating and cooling runs. Two crystallization events were observed, at 884 and 1070 °C. For the standard of the Young's modulus, the specimens shall be prepared so that they are either rectangular or circular in cross section. A bipartite metal mold in the cylinder format was used for the manufacture of the glass and later cut into discs. In order that the cutting process was successful, the glass was subjected to annealing at 660 ° C / 12h, ~15 ° C above Tg. Through FEG-SEM, it was possible to observe crystals of ~40 nm after annealing. Heat treatments conducted at 884 °C for different times resulted in the crystallization of magnetite (Fe3O4). As the heat treatment time increased, both the amount of crystalline phases and the crystallite size increased. The mechanical results showed that the measurement of the Young's modulus by impulse excitation is more reliable since the modulus is measured in the material as a whole and not at points where crystals or amorphous phase can be found.
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