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Pardubice, Czech Republic

Benak M.,University of Trnava | Turna M.,University of Trnava | Ozvold M.,University of Trnava | Nesvadba P.,Explosia Inc. | And 4 more authors.
METAL 2010 - 19th International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2010

Aluminium -Austenitic CrNi steel bimetal was fabricated by explosion welding with parallel arrangement of welded metals. The formed boundary was studied by using microstructural analysis, microhardness measurement, SEM, EDX and EBSD techniques. Mechanical mixing of materials was observed just after joint formation and after annealing. Degradation of boundary was observed at annealing temperatures of 250°C. Amorphous phase was revealed by EBSD method. © 2010 TANGER Ltd., Ostrava.

Benak M.,Slovak University of Technology in Bratislava | Turna M.,Slovak University of Technology in Bratislava | Palcek P.,University of Zilina | Nesvadba P.,Explosia Inc.
Defect and Diffusion Forum | Year: 2010

The aim of the present work was to solve the technology for welding Mg alloy type AZ 63 with aluminium and to assess the quality of the fabricated joints (bimetals-composites). In solving the welding technology, the high affinity of Mg to oxygen has to be considered and therefore as suitable technology either metallurgical joining in vacuum (electron beam etc.) or high-speed solid state welding seem to be feasible. Explosion welding with Semtex S 30 explosive was approved experimentally. Parallel arrangement of welded materials was applied. The more plastic Al material was accelerated. Quality of bonds (bimetals) was assessed by defectoscopy (ultrasound), optical microscopy, microhardness measurement and X-ray microanalysis. It can be generally stated that the basic requirement on joint quality (namely the undulated boundary) was met. The structural composition and absence of inhomogeneities in fabricated bimetals suggest that the desired quality was achieved. © (2010) Trans Tech Publications.

Trso M.,Slovak University of Technology in Bratislava | Benak M.,Slovak University of Technology in Bratislava | Turna M.,Slovak University of Technology in Bratislava | Nesvadba P.,Explosia Inc.
Defect and Diffusion Forum | Year: 2010

As is well known, the explosion welding is considered for a specific type of cold pressure welding. Welded joints fabricated by this technology show a typical undulated boundary, which characterises both, the welding process and bond quality. This technology allows to weld a relatively wide assortment of combinations of various metals and their alloys [1, 2]. This contribution presents the technological procedure for preparation of composite materials based on three metals (trimetals) by use of industrial explosive Semtex S. It concerns the trimetals as structural carbon steel-Cu-Al and structural carbon steel-Ti-Al. For the anodes and cathodes of electrolysers, used for manufacture of aluminium, mostly bimetals were used up to now, as for example the structural carbon steel - Al. However, the mentioned trimetals exert certain priorities over bimetals, regarding mainly the structural stability at elevated temperatures. This also results in higher reliability at breakdown situations and also in longer life of weldments proper. The mentioned trimetals were prepared at Explosia Inc., Research Institute of Industrial Chemistry Pardubice-Semtín. The bond quality was assessed by optical microscopy, microhardness measurement across the bond boundary and also by X-ray microanalysis. © (2010) Trans Tech Publications.

Turna M.,University of Trnava | Ondruska J.,University of Trnava | Nesvadba P.,Explosia Inc.
METAL 2010 - 19th International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2010

Development of explosion welding technology for joining DP 600 steel with austenitic steel type X6CrNiMoTi 17-12-2. Weldability of used combined metals was predicted by application of binary and other diagrams. Welding parameters and conditions (vd , vk , vo , ß, h) were determined. Preparation of weld surfaces and set up of welded materials is described. Quality of fabricated bimetals was inspected by ultrasonic defectoscopy, optical microscopy and microhardness measurements. The interface zone of bimetal was in details assessed by EDX analysis. © 2010 TANGER Ltd., Ostrava.

Zeman S.,University of Pardubice | Ruzicka A.,University of Pardubice | Moncol J.,Slovak University of Technology in Bratislava | Yan Q.-L.,Tel Aviv University | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2016

The tetrahydrate of the tetrapotassium salt of octahydroimidazo-[4,5-d]imidazol-1,3,4,6-tetrasulfonic acid (TACOS-K), an new energetic material, was investigated in terms of its crystal structure, heat of combustion, thermal stability and decomposition kinetics. Its heat of combustion is −5487 ± 96 J g−1 from which a heat of formation of −3150 kJ mol−1 was estimated. It has been found that this compound has a hexagonal crystal space group with a density of 2.026 g mol−1 at 150 K. The organic anionic skeleton of the TACOS-K molecule is distinctly deformed. Six tetraanions interconnected by coordination to the potassium cations and hydrogen bridges to water molecules form hydrophilic as well as hydrophobic cavities. As an intermediate to synthesize cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole, it decomposes at around 31 °C with a first peak temperature range of 46.6–94.3 °C due to loss of water, depending on the heating rates. Hydrolysis of the N–S bonds might play an important role here. Crystalline water evaporation competes with this hydrolysis. TACOS-K has a residual mass of about 46 % at 2 °C min−1, which increases with the heating rate. Peak of the exothermic process occurs at 235.6 °C at the same heating rate with an enthalpy change of 164 J g−1. Dehydration occurs with an energy barrier of 36.7 kJ mol−1 followed by a shoulder mass loss process with a much higher activation energy 110.6 kJ mol−1, while the activation energy for the main exothermic reaction is about 136.2 kJ mol−1. © 2016 Akadémiai Kiadó, Budapest, Hungary

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