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Microstructure and thermomechanical properties of magnesium alloys castings

Lichý P., Cagala M.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

49-54

EN

Magnesium alloys thanks to their high specific strength have an extensive potential of the use in a number of industrial applications. The most important of them is the automobile industry in particular. Here it is possible to use this group of materials for great numbers of parts from elements in the car interior (steering wheels, seats, etc.), through exterior parts (wheels particularly of sporting models), up to driving (engine blocks) and gearbox mechanisms themselves. But the use of these alloys in the engine structure has its limitations as these parts are highly thermally stressed. But the commonly used magnesium alloys show rather fast decrease of strength properties with growing temperature of stressing them. This work is aimed at studying this properties both of alloys commonly used (of the Mg-Al-Zn, Mn type), and of that ones used in industrial manufacture in a limited extent (Mg-Al-Sr). These thermomechanical properties are further on complemented with the microstructure analysis with the aim of checking the metallurgical interventions (an effect of inoculation). From the studied materials the test castings were made from which the test bars for the tensile test were subsequently prepared. This test took place within the temperature range of 20 C - 300 C. Achieved results are summarized in the concluding part of the contribution.

2

Mechanical properties of two manganese steels

Cagala M., Mazancová E., Lichý P., Beňo J., Břuska M., Špirutová N.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 1

9-12

EN

The article is focused on thermomechanical and plastic properties of two high-manganese TRIPLEX type steels with an internal marking 1043 and 1045. Tensile tests at ambient temperature and at a temperature interval 600 C to 1100 C were performed for these heats with a different chemical composition. After the samples having been ruptured, ductility was observed which was expressed by reduction of material after the tensile test. Then the stacking fault energy was calculated and dilatation of both high-manganese steels was measured. At ambient temperature (20 C), 1043 heat featured higher tensile strength by 66MPa than 1045 heat. Microhardness was higher by 8HV0,2 for 1045 steel than for 1043 steel (203HV0,2). At 20 C, ductility only differed by 3% for the both heats. Decrease of tensile properties occurred at higher temperatures of 600 up to 1100 C. This tensile properties decrease at high temperatures is evident for most of metals. The strength level difference of the both heats in the temperature range 20 C up to 1100 C corresponded to 83 MPa, while between 600 C and 1100 C the difference was only 18 MPa. In the temperature range 600 C to 800 C, a decrease in ductility values down to 14 % (1045 heat), or 22 % (1043 heat), was noticed. This decrease was accompanied with occurrence of complex Aluminium oxides in a superposition with detected AlN particles. Further ductility decrease was only noted for 1043 heat where higher occurrence of shrinkage porosity was observed which might have contributed to a slight decrease in reduction of area values in the temperature range 900 C to 1100 C, in contrast to 1045 heat matrix.

3

Dilatometric characterization of foundry sands

Břuska M., Beňo J., Cagala M., Jasinková V.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

9-14

EN

The goal of this contribution is summary of physical - chemistry properties of usually used foundry silica and no - silica sands in Czech foundries. With the help of dilatometry analysis theoretical assumptions of influence of grain shape and size on dilatation value of sands were confirmed. Determined was the possibility of dilatometry analysis employment for preparing special (hybrid) sands with lower and/or more linear character of dilatation.

4

Study of the hot forming conditions of HSLA steel on the tensile testing machine

Kozelsky P., Melecky J., Schindler I., Cagala M.

Hutnik, Wiadomości Hutnicze

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2008

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Vol. 75, nr 8

486-488

EN

The aim of the conducted experimental work was to study the deformation behaviour in the hot state and causes that lead to failure of compactness of a microalloyed steel determined for the tube production. The results of the formability testing are presented, performed by measurements of the strength and plastic properties by means of the tensile test performed at the forming temperatures and displacement speed of the cross beam in the range of 6 to 300 mm/min. It was shown that in the case of this material it is not essentially possible to avoid a defect formation after its cooling by a change of the forming speed.

PL

Celem przeprowadzonego eksperymentu było zbadanie technologicznej plastyczności stali HSLA w warunkach przeróbki plastycznej na gorąco, jak również przyczyn pękania stali mikroskopowych stosowanych do produkcji rur. Zaprezentowano zależność wytrzymałości i właściwości plastycznych badanej stali od warunków odkształcania. Próby rozciągania prowadzono dla temperatur z zakresu przeróbki plastycznej na gorąco tej stali z prędkością w zakresie od 6 do 300 mm/min. Wykazano, że w przypadku badanej stali zmiana prędkości kształtowania nie wpływa w istotny sposób na możliwość uniknięcia defektów po operacji chłodzenia.