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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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Post SPD Material's Recovery in Thermal Exposition

100%
Kvačkaj T., Kováčová A., Kočiško R.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
689-692
EN
The mechanical and thermo-physical properties of Cu-Cr-Zr alloys in dependence on processing conditions were studied. The processing conditions consisted of solution annealing at temperature of 1020°C for 60 min followed by water quenching. This was followed by one equal channel angular pressing pass carried out at ambient temperature, ageing treatment (T_{AT}∈ (20;480⟩°C, t_{AT}∈ ⟨30;150⟩ min) and cooling in water. The maximal strengthening effect coming from dislocations & grain size refinement & precipitation strengthening of ΔHV0.1=130 was achieved at T_{AT}=480°C and for t_{AT}=120 min. From differential scanning calorimetry analysis, two partial exothermal peaks were recognized and classified as major and minor, these peaks are used to determination the stored energy coming from recrystallization and precipitation (ΔH_R and ΔH_P). The maximal value in stored energy of H_{1×ECAP}=2.923 J/g was obtained after 1st ECAP pass.
3
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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.
4
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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.
5
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The Effect of Severe Plastic Deformation and Heat Treatment on CuCrZr Alloys

88%
Kováčová A., Kvačkaj T., Kočiško R., Dragošek L., Lityńska-Dobrzyńska L.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1336-1339
EN
CuCrZr alloy was subjected to equal channel angular pressing method, belonging to the severe plastic deformation group, followed by heat treatment under different ageing conditions to optimize mechanical properties of the alloy. Before equal channel angular pressing, CuCrZr alloy was treated by solution annealing at temperature 1020°C for 1 h. Afterwards, samples were pressed through an equal channel angular pressing die once at room temperature and subjected to artificial ageing under different conditions (200, 400, 450, 480°C for 30, 60, 90, 120, 150 min). Optimization of the CuCrZr alloy was done through the study of mechanical properties and microhardness as a function of ageing temperature and time considering the progress in microstructural/substructural features.
6
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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
7
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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
8
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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.
9
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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
10
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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.
11
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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
12
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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.
13
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Structural Stability of Amorphous Alloy of Modified Finemet Type

76%
Huráková M., Csach K., Juríková A., Miškuf J., Rajňák M., Ďurišin M., Kvačkaj T.
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EN
The Finemet type amorphous alloys are well known as high frequency soft magnetic materials. They have good soft magnetic properties which are characterized by low coercive force and high permeability because of the lack of crystalline anisotropy. The structural stability of the amorphous ribbon of Finemet type modified by Mn, Al and Cr prepared by melt-spinning process was studied using differential scanning calorimetry and dynamical mechanical analysis. With increase of the crystalline portion in the sample, the Curie transition is shifted to the higher temperatures. The magnetic relaxation processes at frequencies above 10⁴ Hz were detected by mass magnetic susceptibility measurement.
14
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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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15
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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
16
Content available remote

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.
17
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The Effect of Cryo-Rolling and Annealing on Magnetic Properties in Non-Oriented Electrical Steel

52%
Kvačkaj T., Bella P., Bidulský R., Kočiško R., Petroušek P., Fedoriková A., Bidulská J., Jandačka P., Lupták M., Černík M., Pernis R.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1105-1107
EN
The goal of the present work is to compare progressive technology - rolling at cryogenic temperature and classical rolling at ambient temperature followed by an investigation of their impact on the final microstructure and the magnetic properties of non-oriented electrical steel. Non-oriented electrical steel is characterized by high magnetic induction, low magnetic losses, and low coercivity. The best magnetic properties are achieved using preferable texture and optimal grain size. In this paper there is analyzed the percentage of different textural components after cryo-rolling and after rolling at ambient temperature. To obtain maps of inverse pole figures, the electron backscatter diffraction method was used. The main contribution of this study was that the samples rolled at cryo conditions and after final annealing reached better magnetic properties than at ambient temperature, which was reflected by low magnetic losses and coercivity.
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