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1
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Analysis of the Fracture Surfaces of New Development Insulated Iron Powder Compounds

100%
Bidulský R., Bidulská J., Kvačkaj T., Actis Grande M.
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vol. 126
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issue 1
154-155
EN
Goal of the present paper is the analysis of the fracture surfaces of an Insulated Iron Powder Compound (IIPC) with different additions of aluminium alloy (0.25, 0.5 and 0.75 wt.%), in order to improve the mechanical properties, evaluated as the transverse rupture strength (TRS) with sufficient magnetic properties (mainly represented by the iron loss and coercivity force). Investigation of microstructure and porosity development concluded that improvements in bending strength and impact values require the reduction of surface oxides during the heat treatment, in order to get a proper load bearing area between the adjacent particles.
2
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Role of Microstructure Discontinuities in the Soft Magnetic Composites with Aluminium Alloy Addition

100%
Bidulský R., Bidulská J., Actis Grande M.
Archives of Metallurgy and Materials
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2013
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issue 2
3
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Analysis of Densification Process and Structure of PM Al-Mg-Si-Cu-Fe and Al-Zn-Mg-Cu-Sn Alloys

100%
Bidulský R., Bidulská J., Actis Grande M.
Archives of Metallurgy and Materials
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2014
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issue 1
4
Content available remote

The Porosity Evaluation during ECAP in Aluminium PM Alloy

100%
Bidulská J., Kvačkaj T., Bidulský R., Actis Grande M.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
553-556
EN
The main aim of this paper is to show porosity evolution during application of various processing conditions including pressing, sintering and equal channel angular pressure. An aluminium based powder (Al-Mg-Si-Cu-Fe) was used as investigated material. After applying different pressing pressures (400 and 600 MPa), specimens were dewaxed in a ventilated furnace at 400C for 60 min. Sintering was carried out in a vacuum furnace at 610C for 30 min. The specimens were processed by single equal channel angular pressure pass. A significant disadvantage of powder metallurgy processing methods is the presence of porosity. Pores act as crack initiators and, due to their presence, the distribution of stress is inhomogeneous across the cross-section and leads to reduction of the effective load bearing area. The equal channel angular pressure process, causing stress distribution in deformed specimens, made the powder particles to squeeze together to such an extent that the initially interconnected pores transform to small isolated pores. The proposed safety diagram includes the combined effect of stress and strain behaviour during equal channel angular pressure. The "safety line" eliminates and quantifies the effect of large pores as a potential fracture initiation sites with respect to the mechanical viewpoint.
5
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Correlation between Microstructure/Fracture Surfaces and Material Properties

100%
Bidulský R., Bidulská J., Actis Grande M.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
548-552
EN
The present paper deals with the evaluation of the effect of different vacuum heat treatments on the microstructure and fracture surfaces of a low alloyed sintered Fe-[1.5Cr-0.2Mo]-0.6C steel, in correlation with the mechanical and plastic properties achieved. The heat treatment consists of the sintering process in vacuum furnace at 1393 K for 1800 s, followed by different cooling conditions and an integrated final tempering at 473 K for 3600 s. The average cooling rates, calculated in the range of 1393 K to 673 K, were 0.1, 0.235, 3, and 6 K/s, respectively. Vacuum heat treatment is supporting the bainitic-martensitic microstructure, the higher the faster cooling rate applied. This provides a marked increase in strength coupled to a decrease in ductility. The decrease of the impact energy after heat treatment is justified by the microstructural changes, especially if a part of bainite is converted to brittle martensite. Samples with bainitic microstructure presented higher impact energies than those with martensitic microstructure. This is fully confirmed by the fracture surface analysis at higher magnification, revealing three main micromechanisms of fracture: brittle, ductile and quasi-cleavage.
6
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Hot Compression Test of Heat Resistant Steel

88%
Fedoriková A., Kvačkaj T., Kočiško R., Bidulský R., Petroušek P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1340-1343
EN
This article deals with the analysis of formability of heat resistant steel type 9Cr-1Mo by physical laboratory simulation - hot compression test. The 9Cr-1Mo steel belongs to modern 9%Cr tempered martensitic steel for high-temperature applications in advanced thermal power plants. The shape of the sample was defined based on numerical simulations. The laboratory simulation of forming process called physical simulation - specifically hot compression test was realized in the temperature range from 500 to 950°C and total deformation in the range from 39 to 52%. Cracks formed during hot compression test in the notches are assessed. Subsequently, the relation between the compression temperature, strain, and crack length was defined. The suitable workability corresponds to the temperature range 650-900°C, it agrees with results of numerical simulations. At a temperature of 900°C there is marginal relative deformation without rupture ε =39.9%, which corresponds to the value according to simulations NCL criteria 0.501.
7
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Study of the High-Temperature Behaviour of Aluminium Alloy En Aw 2014

88%
Bidulská J., Pokorný I., Kvačkaj T., Bidulský R., Grande M.
Archives of Metallurgy and Materials
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2011
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issue 4
8
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Identification of the Critical Pore Sizes in Sintered and Ecaped Aluminium 6XXX Alloy

88%
Bidulská J., Kvačkaj T., Pokorný I., Bidulský R., Actis Grande M.
Archives of Metallurgy and Materials
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2013
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issue 2
9
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The Effects of Chemical Composition on Soft Magnetic Materials Behaviour

88%
Bidulský R., Actis Grande M., Ferraris L., Ferraris P., Bidulská J.
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issue 5
802-803
EN
The main aim of the presented work was to study the effects of chemical composition on the magnetic properties (in terms of B-H characteristics) of an insulated iron powder compound with various addition of the aluminium alloy (0, 5 and 10 wt%). The magnetic properties of the powder were significantly influenced by density and "sintering" effects. The addition of aluminium alloy maintaining suitable values of coercive force, remanence and core losses; this makes the modified insulated iron powder compound a promising soft magnetic material in several applications.
10
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Investigation of Fracture Surfaces of Soft Magnetic Materials

88%
Bidulská J., Kvačkaj T., Bidulský R., Actis Grande M., Ferraris L.
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issue 5
800-801
EN
The present paper focused on the analysis of the fracture surfaces of a new development insulated iron powder compound with the addition of the aluminium alloy in order to improve the mechanical properties. Results show that in the pressed state, mainly pores act as crack initiators and due to their presence the distribution of stress is inhomogeneous across the cross-section and leads to the reduction of the effective load bearing area. Investigation of fracture surfaces concluded that improvements in bonding during the pressing process and heat treatment can be helpful in the development of soft magnetic materials to give a suitable combination between pressing pressure, annealing temperature and time as well as magnetic properties.
11
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New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

88%
Kvačkaj T., Kováčová A., Bidulská J., Bidulský R., Kočičko R.
Archives of Metallurgy and Materials
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2015
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issue 2
12
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Formability Evaluation of Aluminium Alloys by FLD Diagrams

76%
Petroušek P., Kočiško R., Kvačkaj T., Bidulský R., Bidulská J., Fedoriková A., Sabol P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1344-1346
EN
The goal of the present work is evaluated mechanical properties and forming limit diagrams of ambient rolled aluminium alloy based on AlMgSi. Forming limit diagrams are convenient and often used as a tool for the classification of the formability and the evaluation of the forming process of sheet materials. Forming limits of sheet metal are represented in the forming limit diagrams occurring by various deformation states. The most widely used type is the Keeler-Goodwin diagram. Input data got from static tensile test are important for formability evaluating of the thin sheet by mathematical simulations, such as tensile strength, yield strength, elongation, and the strain hardening exponent. The result is a consideration of the suitability of the material for stamping technology.
13
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Porosity Behaviour of Insulated Iron Powder Compounds

76%
Bidulská J., Bidulský R., Petroušek P., Fedoriková A., Katreničová I., Pokorný I.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1384-1386
EN
The goal of the present paper is to determine the porosity behavior of new development insulated iron powder compounds without and with different additions of aluminum alloy Alumix 321 (5 and 10 wt%). A significant disadvantage of PM processing is the presence of porosity. Pores act as crack initiators and, due to their presence, the distribution of stress is inhomogeneous across the cross-section and leads to the reduction of the effective load bearing area. Quantitative image analysis of investigated material treats pores as isolated plane two-dimensional objects in solid surroundings. To describe the dimensional and morphological porosity characteristics, the dimensional characteristic D_{circle} and the morphological characteristics f_{shape} and f_{circle} were explored. Both the morphology and the distribution of pores shows a significant effect on the cold welding or appropriate bonds between adjacent particles.
14
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Interparticle Neck Connections in Innovative Insulated Iron Powder Compounds

76%
Bidulský R., Bidulská J., de Oro R., Hryha E., Maccarini M., Forno I., Actis Grande M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
647-650
EN
Goal of the present paper is the analysis of the interparticle neck connections in a system made of insulated iron powder compounds with different additions of an Al-Mg-Si-Cu alloy (0.25, 0.5 and 0.75 wt%). The introduction of the aluminium alloy powder has been made in order to improve the mechanical properties, evaluated as the transverse rupture strength, without decreasing the magnetic properties (evaluated in terms of iron loss and coercivity force). The fracture analysis of investigated systems puts into evidence the breaking of interparticle neck connections. Heat treatment (at the temperature of 500°C) contributes to the early stages of interparticle neck developments. The chosen aluminium alloy presents a sort of pre-sintering behaviour at 500°C, with the possibility of mass-transport processes around the insulated iron powder compounds. The air heat treatment applied aims at providing an increase in the mechanical behaviour of the material, with a final good rigidity after the cooling process. Fracture surfaces and transverse rupture strength values show that, at 500 MPa, the strength and the area related to the inter-particle necks can be correlated to the occasional broken insulated point-to-point surfaces that hinder the development of inter-particles necks.
15
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Investigation of the Ultrafine-Grained Structure Formation under Different Strain Rates

76%
Kováčová A., Lityńska-Dobrzyńska L., Dutkiewicz J., Kvačkaj T., Bidulský R., Bidulská J., Kočiško R.
Archives of Metallurgy and Materials
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2017
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vol. 62
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issue 2
16
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Microdeformation Processes in Soft Magnetic Compounds

76%
Bidulský R., Bidulská J., Petroušek P., Fedoriková A., Dudrová E., Actis Grande M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1367-1370
EN
Porosity can be defined in different ways. The most frequently used definition is the total porosity, which is the total volume fraction of empty space in the specimen. The presence of pores strongly affects the fracture mode. Besides the evaluation of geometry and quality of connections, fractographic analysis enables a quantification of the important microstructural characteristics of the plane porosity. This quantity allows to quantify the existing relations between microstructure and properties. The fractographic evaluation of the distribution of microdeformation processes in the volume of experimental material demonstrates the influence of porosity on the concentration of deformation flows into the microvolume of connections. Plain porosity contributes to the recognition of critical microstructural defects and therefore, to enable evaluating the relationship between the processing parameters, microstructural constituents, and pores. In the fractography evaluation, the analysis of the quality of interparticle bonding using determination of elementary types of fracture facets allows to interpret the mechanical and plastic properties of investigated materials.
17
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Influence of ECAP-Back Pressure on the Porosity Distribution

76%
Bidulská J., Kvačkaj T., Kočiško R., Bidulský R., Actis Grande M., Donič T., Martikán M.
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EN
The main aim of this paper is to show how back pressure equal channel angular pressing (ECAP-BP) influences the porosity distribution in powder metallurgy (PM) aluminium alloys. When back pressure is applied, the accumulation of damage in deformed samples decreases due to the fact that the shear strain takes place under predominantly compressive stresses. Consequently, ECAP-BP influences the porosity distribution in terms of the severe shear deformation involved. According to the obtained results, interesting applications for this new progressive method in physical and metallurgical research fields are shown.
18
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Characterization of Microstructural and Mechanical Properties after Cold Rolling of an Electro-Sinter-Forged Cu-Sn Alloy

72%
Gobber F. S., Bidulská J., Fais A., Franchini F., Bidulský R., Kvačkaj T., Actis Grande M., Gobber F. S., Bidulská J., Fais A., Franchini F., Bidulský R., Kvačkaj T., Actis Grande M.
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19
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Application of Workability Test to Spd Processing

64%
Kvačkaj T., Kočiško R., Tiža J., Bidulská J., Kováčová A., Bidulský R., Bacsó J., Vlado M.
Archives of Metallurgy and Materials
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2013
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issue 2
20
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Mechanical and Structural Properties of High Purity Al Processed by ECAP

64%
Kvačkaj T., Kočiško R., Pokorný I., Bidulská J., Kvačkaj M., Kováčová A., Bidulský R., Lityńska-Dobrzyńska L., Dutkiewicz J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
557-560
EN
The mechanical properties and substructure formation of high purity aluminium (99.999%) processed by severe plastic deformation method (equal channel angular pressing) were studied. The equal channel angular pressing process was carried out at room temperature by route C (sample rotation around the axis about 180° after each pass) in a die with two channels intersecting at an angle of Φp = 90. The softening mechanism through dynamic recovery was recognized up to 6th equal channel angular pressing pass, however, after that the mechanical strengthening was revealed. The samples after equal channel angular pressing processing were annealed in different temperature and time conditions. The influence of annealing temperature and time on microhardness as well as diameter of grain size were investigated in samples processed by the 4th equal channel angular pressing pass.
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