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1

Hot Deformation Activation Energy of Metallic Materials Influenced by Strain Value

Schindler I., Opěla P., Kawulok P., Sauer M., Rusz S., Kuc D., Rodak K.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

223--228

EN

Suitable and complete sets of stress-strain curves significantly affected by dynamic recrystallization were analyzed for 11 different iron, copper, magnesium, titanium or nickel based alloys. Using the same methodology, apparent hot deformation activation energy Qp and Qss values were calculated for each alloy based on peak stress and steady-state stress values. Linear dependence between quantities Qp and Qss was found, while Qp values are on average only about 6% higher. This should not be essential in predicting true stress of a specific material depending on the temperature-compensated strain rate and strain.

2

Study of Hot Deformation Behavior of CuFe2 Alloy

Schindler I., Sauer M., Kawulok P., Rodak K., Hadasik E., Jabłońska M. Barbara, Rusz S., Ševčák V.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

701--706

EN

Nil strength temperature of 1062°C and nil ductility temperature of 1040°C were experimentally set for CuFe2 alloy. The highest formability at approx. 1020°C is unusable due to massive grain coarsening. The local minimum of ductility around the temperature 910°C is probably due to minor formation of γ-iron. In the forming temperatures interval 650-950°C and strain rate 0.1-10 s-1 the flow stress curves were obtained and after their analysis hot deformation activation energy of 380 kJ·mol-1 was achieved. Peak stress and corresponding peak strain values were mathematically described with good accuracy by equations depending on Zener-Hollomon parameter.

3

Transformation Diagrams of Selected Steel Grades with Consideration of Deformation Effect

Kawulok R., Schindler I., Mizera J., Kawulok P., Rusz S., Opěla P., Podolínský P., Čmiel K. M., Mališ M.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

55--60

EN

The aim of this article was to assess the effect of previous plastic deformation on the transformation kinetics of selected steels with a wide range of chemical composition. Transformation (CCT and DCCT) diagrams were constructed on the basis of dilatometric tests on the plastometer Gleeble 3800 and metallographic analyses supplemented by measurements of HV hardness. Effect of previous deformation on transformation was evaluated of the critical rate of formation of the individual structural components (ferrite, pearlite and bainite) in the case of formation of martensite respect to Ms temperature. Previous plastic deformation accelerated especially diffuse transformations (ferrite and pearlite), temperature of Ms was lower after previous plastic deformation and bainitic transformation was highly dependent on the chemical composition of steel.

4

The Influence of Deformation and Austenitization Temperature on the Kinetics of Phase Transformations During Cooling of High-Carbon Steel

Kawulok P., Podolinský P., Kajzar P., Schindler I., Kawulok R., Ševčák V., Opěla P.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1743--1748

EN

The aim of the performed experiments was to determine the influence of deformation and of austenitization temperature on the kinetics of phase transformations during cooling of high-carbon steel (0.728 wt. % C). The CCT and DCCT diagrams for austenitization temperature 940°C and DCCT diagram for austenitization temperature 1000°C were constructed with the use of dilatometric tests. On the basis of obtained results, a featureless effect of austenitization temperature and deformation on the kinetics of phase transformations during cooling of investigated steel was observed. Critical cooling rates for the transformation of martensite in microstructure fluctuated from 5 to 7°C · s-1 (depending on the parameters of austenitization and deformation), but only at cooling rates higher than 8°C · s-1 a dominant share of martensite was observed in the investigated steel, which resulted in the significant increase of hardness.

5

The Influence of a Cooling Rate on the Evolution of Microstructure and Hardness of the Steel 27MnCrB5

Kawulok P., Schindler I., Mizera J., Kawulok R., Rusz S., Opěla P., Olszar M., Čmiel K. M.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

907--914

EN

The aim of the performed experiments was to determine the influence of a cooling rate on the evolution of microstructure and hardness of the steel 27MnCrB5. By using dilatometric tests performed on the plastometer Gleeble 3800 and by using mathematical modelling in the software QTSteel a continuous cooling transformation diagram for a heating temperature of 850°C was constructed. Conformity of diagrams constructed for both methods is relatively good, except for the position and shape of the ferrite nose. The values of hardness, temperatures of phase transformations and the volume fractions of structural phases upon cooling from the temperature of 850°C at the rate from 0.16°C · s-1 to 37.2°C · s-1 were determined. Mathematically predicted proportion of martensite with real data was of relatively solid conformity, but the hardness values evaluated by mathematical modelling was always higher.

6

Study of the Effect of Deformation on Transformation Diagrams of Two Low-Alloy Manganese-Chromium Steels

Kawulok R., Kawulok P., Schindler I., Opěla P., Rusz S., Ševčák V., Solowski Z.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1735--1741

EN

The work deal with an assembling and comparing of transformation diagrams of two low-alloy steels, specifically 16MnCrS5 and 20MnCrS5. In this work, diagrams of the type of CCT and DCCT of both steels were assembled. Transformation diagrams were assembled on the basis of dilatometric tests realized on the plastometer Gleeble 3800, of metallographic analyses and of hardness measurements. In addition, for comparison, the transformation diagrams were assembled even with use of the QTSteel 3.2 software. Uniform austenitization temperature of 850°C was chosen in case of both steels and even both types of diagrams. In case of both steels, an influence of deformation led to expected acceleration of phase transformations controlled by diffusion and also of bainite transformation. In both cases, the kinetics of martensitic transformation was not significantly affected by deformation.

7

Influence of Heating Parameters on Flow Stress Curves of Low-Alloy Mn-Ti-B Steel

Kawulok P., Schindler I., Kawulok R., Opěla P., Sedláček R.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1785--1792

EN

Influence of the initial grain size on hot deformation behavior of the low-alloy Mn-Ti-B steel was investigated. The uniaxial compression tests were performed in range of the deformation temperatures of 900-1200°C and strain rates of 0.1-10 s-1. One set of samples was heated directly to the deformation temperature, which corresponded to the initial austenitic grain size of 19-56 μm; the other set of samples was uniformly preheated at the temperature of 1200°C. Whereas the values of activation energy, peak stress and steady-state stress values practically did not depend on the initial austenitic grain size, the peak strain values of coarser-grained structure significantly increase mainly at high values of the Zener-Hollomon parameter. This confirms the negative effect of the large size of the initial grain on the dynamic recrystallization kinetics, which can be explained by the reduction in nucleation density.

8

Kinetics of static recrystallization in the coarse-grained Fe–40 at.%Al–Zr–B alloy

Schindler I., Kopeček J., Kawulok P., Jabłońska M., Hadasik E., Jóźwik P., Opěla P., Hanus P., Polkowski W., Bojar Z.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 4

816--826

EN

The aim of works was to describe mathematically the kinetics of static recrystallization of the alloy type Fe–40 at.%Al–Zr–B (with 24.6 Al–0.01 B–0.18 Zr–0.01 C in wt.%) with the coarse-grained structure. The microstructure of the laboratory castings made of this extremely brittle alloy was homogenized by hot rolling of the material in the protective capsules and by the long-term annealing at 1200 °C. An initial microstructure with average grain size 0.77 ± 0.27 mm was obtained. Based on the isothermal plastic deformation tests and EBSD analysis, the static recrystallization kinetics of the prepared coarse-grained B2 iron aluminide after strain 0.20 was mathematically described. Recrystallized fraction depends on deformation/annealing temperature (900–1100 °C) as well as on annealing time. The activation energy of static recrystallization was calculated as 255 kJ mol−1. Competition between dynamic recovery and static recrystallization was proved after strain 0.35 and annealing temperature 1100 °C. Static recrystallization starts relatively easily in the studied alloy, but a very long-term annealing is quite necessary for the complete course of recrystallization. The mean size of recrystallized grains falls with the decreasing annealing temperature (0.47 ± 0.15 mm for temperature 1100 °C, and 0.22 ± 0.04 mm for 900 °C). Even at a temperature of 1200 °C the annealing after deformation should last approx. 1 min for obtaining the fully recrystallized microstructure. That is why the standard hot forming technologies should be combined by an interpass annealing in order to refine sufficiently the coarse grains.

9

Przebudowa mikrostruktury taśm ze stopu na osnowie fazy międzymetalicznej Ni3Al w efekcie obróbki plastycznej na gorąco

Jóźwik P., Polkowski W., Kawulok P., Schindler I., Bojar Z.

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 8

479--481

PL

W pracy przedstawiono analizę wpływu temperatury (1000 i 1200°C) i szybkości izotermicznego ściskania na gorąco (ε =0,1, 1,0 i 10,0 s-1) na przebudowę mikrostruktury drobnoziarnistego stopu na osnowie fazy międzymetalicznej Ni3Al z dodatkami stopowymi cyrkonu i boru. W wyniku przeprowadzonej obróbki obserwowano efekty rekrystalizacji dynamicznej/postdynamicznej, której udział rósł wraz ze zmniejszeniem szybkości odkształcania i wzrostem temperatury procesu.

EN

The analysis of temperature (1000 and 1200°C) and rate of isothermal hot compression (ε =0.1, 1 i 10 s-1)on the microstructure changes of Ni3Albased intermetallic alloy with zyrconium and boron addition wasshownin the paper. It was observed that the performed treatment has influence on dynamic/postdynamic recrystallization which participation increase with decreasing rate of strain and increasing of process temperature.

10

Optimization of Laboratory Hot Rolling of Brittle Fe-40at.%Al-Zr-B Aluminide

Schindler I., Hadasik E., Kopeček J., Kawulok P., Fabík R., Opěla P., Rusz S., Kawulok R., Jabłońska M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 3A

1693--1701

EN

Use of the protective steel capsules enabled to manage the laboratory hot flat rolling of the extremely brittle as-cast aluminide Fe-40at.%Al-Zr-B with the total height reduction of almost 70 %. The hot rolling parameters were optimized to obtain the best combination of deformation temperature (from 1160°C up to 1240°C) and rolling speed (from 0.14 m·s−1 to 0.53 m·s−1). The resistance against cracking and refinement of the highly heterogeneous cast microstructure were the main criteria. Both experiments and mathematical simulations based on FEM demonstrated that it is not possible to exploit enhanced plasticity of the investigated alloy at low strain rates in the hot rolling process. The heat flux from the sample to the working rolls is so intensive at low rolling speed that even the protective capsule does not prevent massive appearance of the surface transverse cracking. The homogeneity and size of product’s grain was influenced significantly by temperature of deformation, whereas the effect of rolling speed was relatively negligible. The optimal forming parameters were found as rolling temperature 1200°C and the rolling speed 0.35 m·s-1. The effective technology of the iron aluminide Fe-40at.% Al-Zr-B preparation by simple processes of melting, casting and hot rolling was thus established and optimized.

PL

Zastosowanie ochronnych stalowych kapsuł pozwoliło na przeprowadzenie laboratoryjnego walcowania na gorąco pasm z niezwykle kruchego odlewanego aluminidku żelaza (stopu na osnowie fazy międzymetalicznej) Fe-40at.%Al-Zr-B, które umożliwiło redukcję wysokości o prawie 70%. Parametry walcowania na gorąco były dostosowywane celem uzyskania korzystnego zakresu temperatury odkształcenia (od 1160°C do 1240°C) oraz prędkości walcowania (od 0.14 m·s−1 do 0.53 m·s−1) dla otrzymania pasma bez pęknięć i rozdrobnienia silnie niejednorodnej mikrostruktury odlewu. Zarówno eksperymenty jak i matematyczne symulacje oparte na MES wykazały, że niemożliwe jest uzyskanie dobrej plastyczności badanego stopu przy niskich prędkościach odkształcenia podczas walcowania na gorąco. Strumień ciepła płynący z próbki na walce jest tak intensywny przy małej prędkości walcowania, że nawet kapsuła ochronna nie zapobiega pojawieniu się powierzchniowych pęknięć poprzecznych. Jednorodność i rozmiar ziarn w materiale silnie zależy od temperatury odkształcenia, podczas gdy wpływ prędkości walcowania jest relatywnie niewielki. Optymalne parametry kształtowania stopu to: temperatura 1200°C oraz prędkość walcowania 0.35 m·s−1. Skuteczna technologia przygotowania aluminidku żelaza Fe-40at.%Al-Zr-B w prostym procesie topienia, odlewania i walcowania na gorąco została w ten sposób ustalona i zoptymalizowana.

11

Wpływ temperatury i prędkości odkształcenia na mikrostrukturę stopu na osnowie fazy międzymetalicznej Ni3Al

Jóźwik P., Polkowski W., Schindler I., Rusz S., Kawulok P., Krawczyk K., Bojar Z.

Hutnik, Wiadomości Hutnicze

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2014

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Vol. 81, nr 8

549--551

PL

W pracy przedstawiono analizę wpływu temperatury i prędkości walcowania na gorąco na ewolucję mikrostruktury wcześniej uplastycznionego, drobnoziarnistego stopu na osnowie fazy międzymetalicznej Ni3Al z dodatkami stopowymi cyrkonu i boru. W efekcie przeprowadzonej obróbki plastycznej na gorąco stwierdzono istotny przyrost umocnienia, względem materiału wyjściowego. Analiza EBSD wykazała lokalną przebudowę struktury materiału na drodze rekrystalizacji dynamicznej w temperaturze 1280OC i przy prędkości odkształcania 17 m/min.

EN

Temperature and deformation strain rate structure changes in hot-rolled, fine-grained Ni3Al-based intermetallic alloy with zyrconium and boron addition were analyzed in the paper. The conducted hot-working leads to significant increase of hardening level than for material in “initial” stage. The EBSD analysis shows structure change by dynamic recrystallization at temperature 1280OC and strain rate 17 m/min.

12

Structural and mechanical properties of laboratory rolled steels high-alloyed with manganese and aluminium

Kuc D., Hadasik E., Niewielski G., Schindler I., Mazancova E., Rusz S., Kawulok P.

Archives of Civil and Mechanical Engineering

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2012

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Vol. 12, no. 3

312--317

EN

The paper deals with rolling conditions, microstructure, as well as basic mechanical properties of four different high manganese steels after laboratory melting, casting, and hot and cold rolling. The stacking fault energy of heats was in the interval of 85–114 mJ m−2 thanks to the high aluminium contents. The heats with the lowest sum of (C+Mn) supported the highest ferrite volume fraction (up to 45%), while the highest sum of (C+Mn) led to 10% ferrite formation. With lower Al/(C+Mn) ratio and lower ferrite fraction higher rolling forces were necessary to be used. Due to heterogeneities of matrixes and observed aluminium oxide complexes differences in mechanical properties were detected. The best results showed the heat with 0.65% C−29.5% Mn−9.0% Al and a stacking fault energy 114 mJ m−2.

13

Influence of finish rolling temperature on properties of middle-and high-carbon steels

Rusz S., Kawulok P., Schindler I., Cizek L., Legerski M., Cmiel K.

Hutnik, Wiadomości Hutnicze

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2008

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Vol. 75, nr 8

508-510

EN

The influence of a change of the finish rolling temperature on the structural characteristics and mechanical properties of 3 selected types of the medium to high-carbon steel (H02C050, H09C070, H09C080) in relation to the intended normalized or thermomechani-cal rolling in the continuous wire rod mill at Trinecke żelezarny a.s^ (further TZ) was assessed. The laboratory rolling mill Tandem in the Institute of modelling and control of forming processes at VSB-Technical University of Ostrava was used for the laboratory experiments. All the rolled products were evaluated on the basis of the metallographic investigations and tensile tests. The resulting properties are a function of the carbon equivalent; they are not dependent, however, on the parameters of the finish rolling.

PL

Oceniono wpływ zmiany temperatury walcowania wykańczającego na charakterystykę strukturalną i właściwości mechaniczne dla 3 wybranych gatunków stali (H02C050, H09C070, H09C080) z grup stali średnio- i wysokowęglowych, w odniesieniu do założonych warunków walcowania normalizującego oraz walcowania z obróbką ćieplno-mechaniczną, realizowanych na walcarce walcówki ciągłej w Trinecke żelezarny a.s. (TZ). W badaniach laboratoryjnych wykorzystano walcarkę Tandem, będącą w posiadaniu Instytutu Modelowania i Sterowania Procesami Przeróbki Plastycznej VSB-Technical University w Ostrawie. Dla próbek pobranych z wszystkich wyrobów walcowanych wykonano badania metalograficzne oraz próby rozciągania. Otrzymane właściwości stali są funkcją równoważnika węgla, są niezależne, natomiast pośrednio zależą od parametrów walcowania wykańczającego.