PROPERTIES OF SQEEZE CAST MGZNAL AND MGZNALCA ALLOYS WITH ICOSAHEDRAL PHASE DURING ANNEALING WITH CONSTANT HEATING RATES

1 KODETOVÁ Veronika
Co-authors:
1 VLACH Martin 1 STULÍKOVÁ Ivana 1 SMOLA Bohumil 1 KEKULE Tomáš
Institution:
1 Charles University in Prague, Faculty of Mathematics and Physics, Prague, Czech Republic, EU
Conference:
24th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, June 3rd - 5th 2015
Proceedings:
Proceedings 24th International Conference on Metallurgy and Materials
Pages:
1507-1512
ISBN:
978-80-87294-58-1
ISSN:
2694-9296
Published:
12th January 2015
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
50 views / 8 downloads
Abstract

The Mg–11.5wt.%Zn–3.0wt.%Al and Mg–5.1wt.%Zn–3.3wt.%Al–0.1wt.%Ca alloys were squeeze cast under a protective gas atmosphere (Ar + 1% SF6). Precipitation reactions were studied by differential scanning calorimetry at heating rates of 0.5 – 30 K/min. Electrical resistometry at 78 K and microhardness (HV0.5) at room temperature were performed additionally. The specimens were subjected to isochronal annealing with steps of 20 K/20 min up to 300 °C. The thermal measurements revealed two exothermic effects during linear heat treatment in the temperature range of 100 – 250 °C at heating rates of 2 – 30 K/min. In agreement to the thermal response, two stages of electrical resistivity decrease were observed in the same temperature range. The lower thermal and absolute resistivity changes were observed in the alloy with Ca-addition. Activation energies obtained from the thermal measurements using the Kissinger method for the two mentioned processes were calculated as Q1 = (124 ± 17) kJ · mol-1 and Q2 = (133 ± 4) kJ · mol-1 in both alloys.

Keywords: Differential scanning calorimetry, electrical resistometry, activation energy, icosahedral phase

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