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1
Content available Microstructure and thermomechanical properties of magnesium alloys castings
100%
Lichý P. , Cagala M.
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tom 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
Content available Manufacturing of Cast Metal Foams with Irregular Cell Structure
80%
Kroupová I. , Radkovský F. , Lichý P. , Bednářová V.
Archives of Foundry Engineering
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2015
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tom Vol. 15, iss. 2
55--58
EN
Metallic foams are materials of which the research is still on-going, with the broad applicability in many different areas (e.g. automotive industry, building industry, medicine, etc.). These metallic materials have specific properties, such as large rigidity at low density, high thermal conductivity, capability to absorb energy, etc. The work is focused on the preparation of these materials using conventional casting technology (infiltration method), which ensures rapid and economically feasible method for production of shaped components. In the experimental part we studied conditions of casting of metallic foams with open pores and irregular cell structure made of ferrous and nonferrous alloys by use of various types of filler material (precursors).
3
Content available Casting routes for porous metals production
80%
Lichý P. , Bednarova V. , Elbel T.
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tom Vol. 12, iss. 1
71-74
EN
The last decade has seen growing interest in professional public about applications of porous metallic materials. Porous metals represent a new type of materials with low densities, large specific surface, and novel physical and mechanical properties, characterized by low density and large specific surface. They are very suitable for specific applications due to good combination of physical and mechanical properties such as high specific strength and high energy absorption capability. Since the discovery of metal foams have been developed many methods and techniques of production in liquid, solid and gas phases. Condition for the use of metal foams - advanced materials with unique usability features, are inexpensive ways to manage their production. Mastering of production of metallic foams with defined structure and properties using gravity casting into sand or metallic foundry moulds will contribute to an expansion of the assortment produced in foundries by completely new type of material, which has unique service properties thanks to its structure, and which fulfils the current demanding ecological requirements. The aim of research conducted at the department of metallurgy and foundry of VSB-Technical University Ostrava is to verify the possibilities of production of metallic foams by conventional foundry processes, to study the process conditions and physical and mechanical properties of metal foam produced. Two procedures are used to create porous metal structures: Infiltration of liquid metal into the mold cavity filled with precursors or preforms and two stage investment casting.
4
Content available Evaluation of Properties of Cast Metal Foams with Irregular Inner Structure
71%
Kroupová I. , Lichý P. , Ličev L. , Hendrych J. , Souček K.
Archives of Metallurgy and Materials
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2018
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tom Vol. 63, iss. 4
1847--1851
EN
Internal structure of metal foams is one of the most important factors that determine its mechanical properties. There exists a number of methods for studying the nature of the inner porous structure. Unfortunately most of these processes is destructive and therefore it is not possible to reuse the sample. From this point of view, as a suitable method seems to be the ability of using the so-called X-ray microtomography (also micro-CT). This is a non-destructive methodology used in a number of fields (industry, science, archaeology, medicine) for a description of the material distribution in the space (e.g. pores, fillers, defects, etc.). In principle, this technology works on different absorption of X-ray radiation by materials with changing proton number. The contribution was worked out in collaboration with experts from the Faculty of Electrical Engineering and Computer Science of the VŠB-Technical University of Ostrava and it is focused on the analysis of internal structure of the metal foam casting with irregular arrangement of internal pores by using micro-CT. The obtained data were evaluated in the commercial software VGStudio MAX 2.2 and in the FOTOMNG system. For the evaluation of these data a new specialized module was introduced in this system. Several methods of pre-processing the image was prepared for the measurement. This preliminary processing consists, for example, from a binary image thresholding for better diversity between the internal porosity and the material itself or functions for colour inversion.
5
Content available Evaluation of Collapsibility of Selected Core Systems
71%
Obzina T. , Merta V. , Rygel J. , Lichý P. , Drobíková K.
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tom Vol. 22, iss. 1
48--52
EN
There are mainly two different ways of producing sand cores in the industry. The most used is the shooting moulding process. A mixture of sand and binder is injected by compressed air into a cavity (core), where it is then thermally or chemically cured. Another relatively new method of manufacturing cores is the use of 3D printing. The principle is based on the method of local curing of the sand bed. The ability to destroy sand cores after casting can be evaluated by means of tests that are carried out directly on the test core. In most cases, the core is thermally degraded and the mechanical properties before and after thermal exposure are measured. Another possible way to determine the collapsibility of core mixtures can be performed on test castings, where a specific casting is designed for different binder systems. The residual strength is measured by subsequent shake-out or knock-out tests. In this paper, attention will be paid to the collapsibility of core mixtures in aluminium castings.
6
Content available Microstructure and Thermomechanical Properties of Magnesium Alloys Castings
70%
Cagala M. , Lichý P.
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7
Content available Some Possibilities of Using Statistical Methods While Solving Poor Quality Production
61%
Lakomá R. , Čamek L. , Lichý P. , Kroupová I. , Radkovský F. , Obzina T.
Archives of Foundry Engineering
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2021
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tom Vol. 21, iss. 1
18--22
EN
This paper presents an overview of a research on six practical cases that were solved in a precise casting company where parts are cast by the mean of the low-wax casting method (investment casting) in order to decrease poor quality production. The steel cast parts production technology by the lost-wax method requires the detailed work procedures observation. On the base of statistical processing data of given types of casting products, it was possible to assess the significance of each particular checking events by using the statistical hypothesis testing. The attention was focused on wax and ceramic departments. The data in technological flow were compared before and after the implementation of the change and statistical confirmative influences were assessed. The target consisted in setting such control manners in order to get the right conditions for decreasing poor quality parts. It was evidenced that the cast part defect cause correct identification and interpretation is important.
8
Content available Mechanical Properties of Two Manganese Steels
61%
Cagala M. , Lichý P. , Beňo J. , Mazancová E. , Břuska M. , Špirutová N.
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9
Content available Mechanical properties of two manganese steels
61%
Cagala M. , Mazancová E. , Lichý P. , Beňo J. , Břuska M. , Špirutová N.
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tom 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.
10
Content available Evaluation of Properties of Cast Metal Foams with Irregular Inner Structure
61%
Kroupová I. , Lichý P. , Ličev L. , Hendrych J. , Souček K.
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nr 4
11
Content available Some Possibilities of Using Statistical Methods While Solving Poor Quality Production
57%
Lakomá R. , Čamek L. , Lichý P. , Kroupová I. , Radkovský F. , Obzina T. , Lakomá R. , Čamek L. , Lichý P. , Kroupová I. , Radkovský F. , Obzina T.
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12
Content available Preparation and Evaluation of Properties of Cast Metallic Foams with Regular Inner Structure
41%
Lichý P. , Kroupová I. , Radkovský F. , Elbel T.
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