Author(s):
1. Milan Bizjak, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia
2. Borut Kosec, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia
3. Blaž Karpe, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia
4. Aleš Nagode, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia
5. Mirko Gojic, University of Zagreb, Faculty of Metallurgy, Croatia

Abstract:
Innovative idea, concept and construction of the system for the in-situ detection of microstructural transformations was conducted at Faculty of Natural Sciences and Engineering, University of Ljubljana, with the support of the Slovenian industry. This device is intended for both: research laboratories and industry. The beginning of its construction dates back to 2008, and the first measurements were successfully implemented in 2011. To date, we have analyzed the phase transitions in rapidly solidified copper and aluminum alloys, nickel and nickel alloys, dental alloys and several types of steel for Slovenian steel producers. A measuring system with multiple patent solutions is an important acquisition for education in the field of materials, metallurgy, mechanical engineering and manufacturing technologies for graduate and post graduate students. Since the electrical resistance is one of the most sensitive structural properties of the materials, we used it for the detection of microstructural changes created by phase transformation or chemical reactions. The measurement of electrical resistance is carried out through measurement of voltage change at a known direct current to the sample. For accurate measurement of the sample electrical resistance, a four-point method has been used, which eliminate the influence of measuring wire resistance. The undesired self-heating of the sample by measuring current is minimized by changing the polarity of the power source. An automated system for measuring the electrical resistance as a function of temperature allows the study of thermally activated processes in a variety of thin layers of metallic glasses, quasi-crystalline alloys, rapidly solidified alloys and other metallic and non-metallic materials in the crystalline or amorphous state. Measurements can be performed in an inert, reduction or oxidation atmospheres. Ensured accuracy of the measuring system enables calculating the kinetic parameters of the microstructural transformations. Thermo-electrical measurement results are presented in the form of temperature and/or time electrical resistance dependency curves. System for following the microstructural transformations by measuring the electrical resistance is composed of three basic parts: heating system, vacuum system and monitor/control unit. The measuring system allows easy setting of measurement parameters, data acquisition and their processing. A system for in situ measurement of the electrical resistance as a function of time and temperature can be used in a wide temperature range, and satisfies the requirements: the measured resistance is stable and does not vary by more than 0.01%, during the measurement procedure heating rate and temperature are precisely measured.

Key words:
electrical resistance,measurement,in-situ detection,microstructure,transformation

Thematic field:
SYMPOSIUM A - Science of matter, condensed matter and physics of solid states

Date of abstract submission:
10.07.2017.

Conference:
Contemporary Materials 2017 - Savremeni Materijali