1. The characterization of phase transformations in rapidly solidified Al-Fe and Cu-Fe alloys through measurements of the electrical resistance and DSCMilan Bizjak, Ladislav Kosec, Borut Kosec, Ivan Anžel, 2006, izvirni znanstveni članek Opis: For the characterization of the phase transformations in the alloys during the heat treatment the various methods of the thermal analyses are available. Thermogravimetry, differential thermal analysis (DTA) and the differential scanning calorimetry (DSC) are the most frequently used methods. The phase transformations proceed in two stages, i.e. nucleation and the growth of the new phase. Both processes are closely linked with the movement of the atoms. Rapidly solidified alloys often contain the elements with the low diffusivity. During the transition from the unstable to the stable state the energy changes are small, therefore the characterization of the changes by DTA, DSC is very difficult and could not be measured. During the heat treatment the phase transformations of the rapidly solidified alloys of Al-Fe and Cu-Fe were successfully detected by the simultaneous measurements of the electrical resistance, and were compared by the DSC method. By determination of the temperature regions of the phase transitions or temperatures, where the dynamics of the changes is maximal, the samples were heat treated and analysed by the scanning and transmission electron microscopy respectively.
Ključne besede: rapidly solidified Al-Fe alloy, rapidly solidified Cu-Fe alloy, transformations, electrical resistance, differential scanning calorimetry
Objavljeno v DKUM: 03.07.2017; Ogledov: 1966; Prenosov: 150
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2. Monitoring of directional solidification with simultaneous measurements of electrical resistance and temperatureMihael Brunčko, Ivan Anžel, Alojz Križman, 2003, izvirni znanstveni članek Opis: WE present the efficiency of simultaneous electrical resistance and temperature (ERT) measurements for monitoring the position, X, and the growth rate, V, of the solidification front during the directional solidification of alloys. On alaboratory device for directional solidification (Bridgman-type furnace), theeutectic Pb-Sn alloy was solidified at five different pulling rates, VP, with a constant imposed temperature gradient, GP. During directional solidification, the electrical resistance and the temperature changes were measured simultaneously in the experimental samples. The results of the experiments show that simultaneous measurement of ERT enables not only the determination of the average growth rate, V, during directional solidificationbut also its fluctuation over the total measurement length of the sample.
Ključne besede: metallurgy, Pb-Sn alloy, directional solidification, electrical resistance measurements, temperature measurements
Objavljeno v DKUM: 01.06.2012; Ogledov: 1936; Prenosov: 103
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3. In-situ monitoring of internal oxidation of dillute alloysMihael Brunčko, Ivan Anžel, Albert C. Kneissl, 2007, izvirni znanstveni članek Opis: This paper presents a non-destructive measurement method that enables identification and characterization of phenomena during internal oxidation of metallic materials as well as monitoring the kinetics of internal oxidation using "in-situ" electrical resistance measurements. A special laboratory device, based on the unique measurement cell, for the electrical resistance measurements at high temperatures and the model for electrical resistance transformation into an instantaneous microstructure were developed. To accomplish this, the process of internal oxidation was divided into the sequence of the key partial reactions that were presented in the model as the parallel andžor serial connected time variable resistors in the electrical circuit. The validity of the transformation model was experimentally confirmedby internal oxidation of Ag-Sn (2 at.% Sn) alloy at different oxidation temperatures in air atmosphere. The comparison of the results obtained by "in-situ" electrical resistance measurements with those obtained by metallographic analysis and Wagnerćs theory shows that the novel method presents a more effective tool for monitoring of internal oxidation kinetics. The method identifies also the microstructural defects and their influences onthe kinetics of internal oxidation.
Ključne besede: metallurgy, Ag-Sn alloy, internal oxidation, electrical resistance
Objavljeno v DKUM: 01.06.2012; Ogledov: 1834; Prenosov: 44
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