Papers by Author: Kinga Rodak

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Authors: Anna Urbańczyk-Gucwa, Kinga Rodak, Adam Płachta, Joanna Sobota, Zbigniew Rdzawski
Abstract: The results of the microstructure and hardness investigations of the Cu-0.8Cr alloy after application of severe plastic deformation (SPD) implemented by rolling with the cyclic movement of rolls (RCMR) are presented in this paper. Performed substructure investigations showed that using the RCMR method can refine the microstructure of Cu-0.8Cr alloy to the ultrafine scale. The structure of the Cu-0.8Cr alloy was analyzed using light microscope (LM) and scanning transmission electron microscope (STEM). The quantitative studies of the substructure was performed with "MET-ILO" software, on the basis of images acquired on STEM microscope.
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Authors: Kinga Rodak, Jacek Pawlicki, Marek Tkocz
Abstract: The results presented in this paper are concerned with the microstructure and the mechanical properties of the AlMg5 alloy subjected to severe plastic deformation by multiple compression in two orthogonal directions. Four experiments with an increasing number of passes were conducted on the Gleeble MAXStrain system in order to obtain various effective strain levels. The deformed microstructure was investigated by means of the light microscopy (LM) and the scanning transmission electron microscopy (STEM). The mechanical properties were determined for the most deformed, central parts of samples. Investigations revealed that severe cold deformation of the AlMg5 alloy leads to strong grain refinement. Moreover, fragmentation of large intermetallic inclusions and their regular distribution were obtained in the analysed, central parts of the samples. Microstructural changes led to significant improvement in the strength properties. After reaching the effective strain of 9, the AlMg5 alloy exhibited UTS, YS and HV values almost two times higher than corresponding values determined for the starting, annealed material.
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Authors: Kinga Rodak, Jacek Pawlicki, Krzysztof Radwański, Rafal M. Molak
Abstract: In this study, commercial Cu was subjected to plastic deformation by compression with oscillatory torsion. Different deformation parameters were adopted to study their effects on the microstructure and mechanical properties of Cu. The deformed microstructure was characterized by using scanning electron microscopy (SEM) equipment with electron backscattered diffraction (EBSD) facility and scanning transmission electron microscopy (STEM). The mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. Can be found, that process performed at high compression rate and high torsion frequency is recommended for the refining grain size. The size of structure elements: average grain size (D) and subgrain size (d) reached 0.42 m and 0.30 m respectively, and the fraction of high angle boundaries was 35%, when the sample was deformed at a torsion frequency f= 1.6 Hz and compression rate v=0.04 mm/s. Deformation at these parameters leads to an improvement in strength properties. The strength properties are about two times greater than the initial state.
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Authors: Kinga Rodak, Grzegorz Moskal
Abstract: The evaluation of microstructure and the thermal diffusivity of copper subjected to severe plastic deformation using multi-axial compression was investigated. The investigations were performed on copper (M1E grade) processed to effective strain at range f =1-14.9. The multi- axial compression resulted in an refining structure. The evolution of dislocation structure, misorientation distribution, crystalline size were observed by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The thermal diffusivity measurements were performed by using the LFA427 apparatus based on the laser-flash method. Subgrain and grain size for f =3.7 reaches about 250 nm and 550 nm respectively. The local recrystallization occur in analyzed microarea especially at f =7.5 and delay the reduction of sub(grain) size. In consequence no more large changes in structure occur during further processing up to the largest strain. The microstructural phenomena have an influence on the thermal parameters. The value of this parameters insignificantly decreased with increasing of accumulated strain.
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Authors: Magdalena Jabłońska, Wojciech Moćko, Kinga Rodak, Rafał Michalik, Anna Śmiglewicz
Abstract: The article presents the dynamic mechanical properties of two types of high manganese austenitic steels. The investigation were carried out for the wide range of strain rates from 1×10-4s-1 up to 4×103s-1 using servo-hydraulic testing machine and Hopkinson bar for the quasi-static and dynamic loading regime, respectively. The mechanical properties at different strain rates as well as the SEA indicator calculated were carried out on the base of the results of impact tests. In the next step, the microstructure of the steel after different deformation rate was observed and analyzed by light microscope in order to disclose a TWIP effect.
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Authors: Kinga Rodak, Jacek Pawlicki
Abstract: The microstructure of Al processed by compression with oscillatory torsion (COT) method have been studied. This method was applied to refine the grain structure to ultrafine dimension. The aim of the study was to examine how severe plastic deformation technique (COT) - alter the microstructure. The second aim is to understand the mechanism of grain refinement. The microstructure was characterized using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron back scattered diffraction (EBSD) facility.
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Authors: Kinga Rodak, Krzysztof Radwański, Rafal M. Molak
Abstract: . In this study, commercial Al was subjected to plastic deformation by multi-axial compression. The microstructure and mechanical properties in dependence on effective strain were studied. Aluminum was processed to effective strain f = 9.6. The misorientation distribution and subgrain/grain size were analyzed by using a scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The dislocation microstructure was investigated by a scanning transmission electron microscope (STEM). The mechanical properties as: yield strength (YS), ultimate tensile strength (UTS), uniform and total elongation were performed on MTS QTest/10 machine equipped with digital image correlation method (DIC). Deformation of Al by the multi-axial compression leads to grain refinement to ultra-fine grains (UFGs) and improvement in strength properties. Material exhibits the following strength parameters: UTS: 129 MPa, YS: 124 MPa after deformation at f = 9.6. These values are about two times higher compared with initial state.
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Authors: Kinga Rodak, Krzysztof Radwański
Abstract: Different techniques have been used to introduce large strains into metals, for example torsion under pressure (HPT), cyclic extrusion compression (CEC), equal channel angular extrusion (ECAE), or accumulative roll bonding (ARB). Recent investigations are focused on analyzing new and alternative techniques for introducing severe plastic deformation (SPD) and to compare SPD techniques in terms of grain refinement and enhancement of properties. Compression with oscillatory torsion was applied to 0H18N9 austenitic steel to achieve a large strains. The microstructure was characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Formation of deformation twins and shear bands are responsible for the structure refinement in materials with low stacking fault energies (SFEs) such as austenitic steel. The investigations revealed, that nano-sized grains of 0H18N9 steel after processing by compression with oscillatory torsion are found in three different types of regions.
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Authors: Kinga Rodak, Grzegorz Moskal, Andrzej Grabowski
Abstract: In article the influence of large effective deformation on microstructure, thermal diffusivity and electrical conductivity is described. The tested material was monocrystalline aluminum deformed by the cyclic extrusion compression (CEC) method. The evolution of misorientation distribution, sub(grain) size was determined by using electron back scattered diffraction (EBSD) technique. The second part of the study was to evaluation of thermal diffusivity by using the laser-flash method. The LFA 427 laser-flash facility were applied. The electrical properties as electrical impedance was made by impedance bridge RLC type. The obtained results show that with increase of deformation the insignificant decrease in thermal diffusivity and electrical conductivity occurred.
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Authors: Bartosz Chmiela, Maria Sozańska, Kinga Rodak
Abstract: Aero engine turbine blades made of nickel-based superalloys are critical components in flight safety. Therefore, it is very important to make sure that the chemical composition, phase composition and microstructure are suitable. However, due to their chemical compositions, superalloys are prone to many transformations and the formation of deleterious phases, which deteriorate the mechanical properties. Hence, investigations concerning the structural stability and phase identification—especially topologically close-packed phases (TCP)—are necessary. Because the volume fractions of these phases are generally small, phase identification should be performed by nanodiffraction techniques in a scanning transmission electron microscope (STEM) and electron backscatter diffraction in a scanning electron microscope (EBSD/SEM). These methods complement each other, but each of them is characterized by different difficulties and limitations. In this paper we present the possibilities and limitations of phase identification in single crystal CMSX-4 superalloy after long thermal exposure.
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