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1

Electroplastic Effect of High Manganese Austenitic Steel

Zimniak Z., Dobras D.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 1

431--436

EN

The article presents the results of the investigations performed on high manganese austenitic steel which underwent the test of uniaxial tension, with the application of electric current impulses. The application of low voltage impulse alternating current of high intensity during the plastic deformation of the examined steel caused the occurrence of the electroplastic effect, which changed the shape of the stress-strain curve. A drop of flow stress and elongation of the tested material was observed in the case of the application of electric current impulses, in respect of the material stretched without such impulses and stretched at an elevated temperature. The analysis of the morphology of the fractures showed differences between the samples tested under the particular conditions. An analysis of the alloy’s microstructure was also performed under different conditions. The application of electric current impulses can have a significant influence on the reduction of the forces in the plastic forming processes for this type of steel.

2

Temperaturowe aspekty odkształcenia plastycznego stali austenitycznej wysokomanganowej przeznaczonej do produkcji drutu

Kozłowska A., Grajcar A., Adamiec A.

Hutnik, Wiadomości Hutnicze

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2017

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Vol. 84, nr 1

30--33

PL

W pracy zbadano możliwości zastosowania stali austenitycznej wysokomanganowej jako nowoczesnego materiału do produkcji drutów stalowych o wysokim potencjale odkształcenia plastycznego na zimno. Odkształcenie plastyczne symulowano w jednoosiowej próbie rozciągania w zakresie temperatury od 20°C do 200°C. Przeanalizowano rodzaj dominującego mechanizmu umocnienia (efekt TRIP lub/i efekt TWIP) w zależności od temperatury odkształcenia. Rozwój mikrostruktury monitorowano w przerywanych próbach rozciągania do odkształcenia wynoszącego 5%, 10%, 20% oraz do zerwania.

EN

In this study, the possibilities of the application of high-Mn austenitic steel as a material for the production of steel wires with high potential of cold plastic deformation were examined. The plastic deformation was simulated in a uniaxial tensile test in a temperature range of 20°C to 200°C. The dominant effect of strengthening mechanism of the steel (TRIP or/ and TWIP effect) depending on the temperature of plastic deformation was determined. Development of the microstructure was monitored in interrupted tensile tests to deformation of 5%, 10%, 20% and up to rupture.

3

Plastyczność i mikrostruktura wysokomanganowej stali X55MnAl25-5 z efektem TWIP po próbach skręcania

Jabłońska M., Tomaszewska A., Bednarczyk I., Płachta A., Śmiglewicz A.

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 9

595--598

PL

Rozwój przemysłu motoryzacyjnego, kolejowego czy militarnego wymaga prowadzenia prac badawczych w obszarze nowych wysokomanganowych stali z grupy AHSS. Stale te w zależności od zawartości Mn i Al, czyli głównych pierwiastków stopowych, wykazują skłonność do odkształcania w oparciu o pewien szczególny mechanizm, zależny od wartości energii błędu ułożenia austenitu EBU. Zatem wyróżnić możemy stale wykazujące indukowaną odkształceniem przemianę martenzytyczną (stale z efektem TRIP), indukowane odkształceniem bliźniakowanie mechaniczne (stale z efektem TWIP) oraz indukowane odkształceniem tworzenie mikropasm ścinania (stale z efektem MBIP). W niniejszej publikacji przedstawiono wyniki badań wpływu parametrów skręcania na właściwości oraz strukturę austenitycznej stali X55MnAl25-5 wykazującej efekt TWIP. Badana stal została wyprodukowana na drodze klasycznego odlewania wlewków, które dalej walcowano na pręty okrągłe. Proces prowadzono na finalny wymiar 15 mm w zakresie temperatury 1150÷900°C. Przeprowadzono analizę wpływu parametrów odkształcania plastycznego na gorąco w zakresie temperatury 800÷1100°C na właściwości i strukturę badanej stali w próbach skręcania na plastomerze skrętnym. Wykazano, że badana stal charakteryzuje się bardzo korzystną odkształcalnością. Ujawniono, że w sposób efektywny proces odbudowy zdefektowanej struktury ustala się podczas odkształcania stopu w temperaturze 1000°C z udziałem dynamicznej rekrystalizacji.

EN

The development of the automotive, rail or military industries requires conducting research in the area of new high-Mn steel with a group of AHSS. These steels depending on the content of Mn and Al which is the main alloying elements tend to deform based on a specific mechanism, depending on the value of stacking fault energy of austenite EBU. Thus, we can distinguish steels which showing during deformation martensitic transformation (effect TRIP), mechanical twinning (effect TWIP) and creating shear bands and microbands (effect SIP/MBIP). This publication presents the results of research of torsion parameters on the properties and structure of austenitic X55MnAl25-5 steel belong to the group of TWIP steels. The steel was produced by classical casting to obtain ingots which further rolled to round bars. The process was performed on the final size of 15 mm in the temperature range 1150÷900°C. Analysis of the influence parameters of plastic deformation in hot torsion tests in the temperature range 800 to 1100°C on the properties and structure of the examined steels were carried out. It has been shown that the tested steel has a very favorable formability. It is disclosed that an effective structure rebuilding determined during deformation at 1000°C involving dynamic recrystallization.

4

Ocena struktury stali wysokomanganowych po procesach odkształcenia

Jabłońska M., Śmiglewicz A., Tomaszeska A., Horzelska K.

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 1

31--35

PL

Rozwój takich gałęzi przemysłu, jak przemysł motoryzacyjny czy militarny, koncentruje się w ostatnich latach na prowadzeniu prac badawczych w obszarze nowych wysokomanganowych stali z grupy AHSS. Zależnie od zawartości Mn, Al i Si stale te wykazują określoną wartość EBU, a tym samym charakterystyczny mechanizm odkształcenia, taki jak indukowana odkształceniem przemiana martenzytyczna (efekt TRIP), indukowane odkształceniem bliźniakowanie mechaniczne (efekt TWIP) oraz indukowane odkształceniem tworzenie mikropasm ścinania (efekt MBIP). W artykule przedstawiono wyniki badań wpływu parametrów obróbki cieplno-plastycznej na wybrane właściwości oraz strukturę austenitycznej stali X45MnAl20-3 wykazującej efekt TWIP. Badana stal została wyprodukowana na drodze klasycznego odlewania do miedzianego krystalizatora, uzyskując wlewki o wymiarach 100×100 mm, które poddano walcowaniu w 4 przepustach na końcową grubość 12 mm i 3 mm. Temperatura końca walcowania wynosiła 950°C, a blachy po ostatnim przepuście chłodzono w powietrzu oraz wodzie. Przeprowadzono analizę struktury i właściwości mechanicznych otrzymanych blach oraz analizę wpływu parametrów odkształcenia plastycznego na strukturę badanej stali w próbach ściskania w zakresie temperatury 850°C÷1100°C. Wykazano, że badana stal ma dobre własności wytrzymałościowe oraz bardzo korzystną odkształcalność. W próbach ściskania ujawniono, że równowaga pomiędzy procesami umacniania i odbudowy struktury ustala się podczas odkształcania stopu we wszystkich temperaturach, a zmiany mikrostruktury wskazują na zachodzenie efektów charakterystycznych dla procesów dynamicznej odbudowy w trakcie odkształcania na gorąco badanej stali.

EN

The development of such industries as automotive and military focus in recent years to conduct research in the area of new highmanganese steel from a group of AHSS. Depending on the content of Mn, Al and Si these steels exhibit specific SFE value and thus the characteristic deformation mechanism such as transformation induced plasticity (TRIP effect), mechanical twinning induced plasticity (TWIP effect) and micro bands induced plasticity (effect MBIP). The paper presents the results of the influence of thermo-mechanical treatment parameters on the selected mechanical properties and changes of microstructure of austenitic high manganese TWIP steel X45MnAl20-3. The steel has been produced by conventional casting of copper crystallizer to give ingots of dimensions 100 × 100 mm and then subjected to rolling to the final thickness of 12 mm and 3 mm. Temperature end of rolling was 950°C, and the sheet was cooled in air and water. An analysis of the structure and mechanical properties of the obtained sheet was performed. Moreover the analysis of the influence of hot plastic deformation parameters on the microstructure and properties of researched steel structure during the compression tests in the range of temperature from 850°C to 1100°C was carried out. Established, that the steel has good mechanical properties and a very favorable ductility, as demonstrated by the value of elongation in a tensile test. The compression tests revealed that the balance between the processes of strengthening and rebuilding of the structure is determined during deformation the steel at all temperatures, and changes in microstructure indicate a characteristic for the dynamic recovery process phenomena disclosured.

5

Microstructure and Texture Evolution During Cold-Rolling in the Fe-23Mn-3Si-3Al Alloy

Kowalska J., Ratuszek W., Witkowska M., Zielińska-Lipiec A., Kowalski M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 3A

1789--1794

EN

Fe–23wt.%Mn–3wt.%Si–3wt.%Al alloy was cast, homogenized at 1150ºC, hot-rolled at temperatures between 1200ºC and 900ºC and next cold-rolled from 5% up to 40% reductions in thickness. Microstructure and texture of this alloy, which has a low stacking fault energy, were defined after cold-rolling. Investigation of transmission electron microscopy and X-ray diffraction showed that mechanical twinning and martensitic transformations (γfcc→εhcp and γfcc→εhcp→α′bcc) took place during cold-rolling. The crystallographic Shoji-Nishiyama (S-N) {00.2}ε║{111}γ, <11.0>ε ║ <110>γ and Kurdjumov-Sachs (K-S) {111}γ║{101}α’, <101>γ║<111>α’ relations between martensite (ε, α’) and austenite (γ), were found in the coldrolled material.

PL

W artykule zamieszczono wyniki badań mikrostruktury i tekstury otrzymane dla stopu Fe–23%Mn–3%Si–3%Al (% masowe). Po odlaniu wlewek homogenizowano przy temperaturze 1150ºC, walcowano na gorąco w zakresie temperatur 1200ºC-900ºC i następnie walcowano na zimno do odkształceń od 5% do 40%. Wyniki badań uzyskane przy użyciu transmisyjnej mikroskopii elektronowej i metod dyfrakcyjnych wskazują, że podczas odkształcenia plastycznego na zimno w stopie zachodzi mechaniczne bliźniakowanie i przemiana martenzytyczna. Występują zależności krystalograficzne pomiędzy austenitem (faza γ) i martenzytem (faza ε i faza α’), które opisują zależności: Shoji-Nishiyama {00.2}ε || {111}γ, <11.0>ε || <110>γ i Kurdjumowa-Sachsa {111}γ || {110}α, <110>γ || <111>α.

6

Porównanie właściwości mechanicznych i mikrostruktury stali wyskomanganowych z efektem TWIP odkształcanych plastycznie na gorąco

Jabłońska M.

Hutnik, Wiadomości Hutnicze

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2014

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Vol. 81, nr 8

545--548

PL

W artykule zaprezentowano porównanie wyników badań właściwości i mikrostruktury dla dwóch austenitycznych stali wysokomanganowych, poddanych próbie ściskania na gorąco. Przeprowadzono analizę wpływu parametrów odkształcania plastycznego, takich jak: temperatura i prędkość odkształcenia na maksymalne naprężenie uplastyczniające i mikrostrukturę badanych stali. Wykazano zależność maksymalnego naprężenia uplastyczniającego od prędkości i temperatury odkształcania. W mikrostrukturze obu badanych stali obserwowano efekty charakterystyczne dla procesów dynamicznej odbudowy w trakcie odkształcania na gorąco.

EN

In the article comparing findings of the property and microstructures were presented for two austenitic high-manganese steels, subjected to the hot compression test. Analysis of the influence of parameters of plastic deformation such steels as the temperature and the strain rate, to properties i.e. the maximum stress and the microstructure examined was conducted. A dependence of the maximum stress on the strain rate and temperatures of deformation were demonstrated. In the microstructure of both examined steels effects characteristic of processes of the dynamic recrystallization are being observed in the course of deformation process.

7

Corrosion resistance of high-manganese austenitic steels

Grajcar A., Kołodziej S., Krukiewicz W.

Archives of Materials Science and Engineering

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2010

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Vol. 41, nr 2

77-84

EN

Purpose: The aim of the paper is to compare the corrosion resistance of two new-developed high-manganese austenitic steels in 1N H2SO4 and 3.5% NaCl solutions. Design/methodology/approach: The steels used for the investigation were thermo-mechanically rolled and then solution heat-treated from a temperature of 850°C. Corrosion resistance of investigated steels was examined using the immersion test. The specimens were weighed and dipped in the prepared solutions for 100 h. After the test, the percentage weight loss was calculated. The metallographic investigations of corrosion damages included light and scanning electron microscope observations both in the polished and etched states. Findings: It was found that after the thermo-mechanical processing one steel is characterized by an austenitic structure with numerous annealing twins, whereas in the second steel ε and α' martensite plates in an austenitic matrix were observed. According to the results of the immersion tests it was found that the examined steels exhibit a comparable corrosion resistance. They show very poor corrosion resistance in H2SO4 solution and low corrosion resistance in NaCl medium. The weight loss in chloride solution is much lower, what is explained by different corrosion mechanisms. In both the solutions, the intensive general corrosion and corrosion pitting were observed. In acidic medium they are created in a way of hydrogen depolarization and in NaCl in the way of oxygen depolarization. Research limitations/implications: To investigate in more detail the corrosion behaviour of high-manganese austenitic steels, the investigations should include polarization tests and an analysis of corrosion products. Practical implications: The obtained results can be used to search for the appropriate way of improving the corrosion resistance of high-manganese steels with a single-phase austenitic structure as well as the austenite structure containing ε and α' martensite. Originality/value: The corrosion resistance of two types of advanced high-strength high-manganese austenitic steels with different initial structures was compared in acidic and chloride solutions.

8

Corrosion behaviour of Fe-Mn-Si-Al austenitic steel in chloride solution

Opiela M., Grajcar A., Krukiewicz W.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 2

159-165

EN

Purpose: The aim of the paper is to investigate the corrosion behaviour of the new-developed high-manganese austenitic steel in 0.5n NaCl solution. Design/methodology/approach: The steel used for the investigation was thermomechanically rolled and solution heat-treated from a temperature of 850°C. Corrosion resistance of investigated steel was examined using weight and potentiodynamic methods. In the weight method, the specimens were immersed in the prepared solution for 24h. In the potentiodynamic method, anodic polarization curves with a rate of potential changes of 1 mV/s in the anodic direction were registered. After the current density being equal 1 mA/cm2 was achieved, the direction of polarization has been changed. Basing on the registered curves, the pitting potential, repassivation potential, polarization resistance and corrosion current were determined. Findings: It was found that the steel is characterized by a partially recrystallized austenitic microstructure with numerous annealing twins and slip bands. According to the results of potentiodynamic analyses it was found that the samples of examined steel show poor corrosion resistance in the NaCl solution. The observed corrosion pits are related to the chemical composition. It is connected with the high dissolution rate of Mn and Fe atoms in NaCl solution. Fractographic analyses of samples revealed corrosion products on their surface in a form of pits with diversified size. Research limitations/implications: To investigate in more detail the corrosion behaviour of high-manganese steel, the investigations should include steels with a wider Al concentration. Practical implications: The obtained results can be used for searching the appropriate way of improving the corrosion resistance of a modern group of high-manganese austenitic steels. Originality/value: The corrosion behaviour in chloride solution of a new-developed Fe-Mn-Si-Al steel was investigated.

9

Hot-working behaviour of high-manganese austenitic steels

Dobrzański L. A., Grajcar A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 1

7-14

EN

Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working. Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator. Findings: It was found that they have austenite microstructure with numerous annealing twins in the initial state. Continuous compression tests realized in the temperature range from 850 to 1050*C with the strain rate of 10s -1 enabled determination of yield stress values and values of εmax deformations-corresponding to maximum flow stress. It was found that initiation of dynamic recrystallization requires true strain equal at least 0.29. Holding of steel after plastic deformation allowed determining the progress of recrystallization in the function of isothermal holding time. Determined half-times of recrystallization at 900oC after deformation with 25% of reduction are equal 32 and 17s for 27Mn-4Si-2Al-Nb-Ti and 26Mn-3Si-3Al-Nb-Ti steel, respectively. Several-stage compression tests with true strain of 0.29 permit to use dynamic recrystallization for shaping fine-grained microstructure of steel in the whole range of deformation temperature. Decreasing true strain to 0.23 limits the course of dynamic recrystallization to two first deformation cycles. In two final cycles of deformation, as well as in the whole range of hot-working realized with true strain of 0.19-dynamic recovery is the process controlling strain hardening. Practical implications: The obtained microstructure-hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures. Originality/value: The hot-working behaviour and microstructure evolution in various conditions of plastic deformation for new-developed high-manganese austenitic steels with Nb and Ti microadditions were investigated.

10

Hot rolling of steel with TWIP effect

Kliber J., Kursa T., Schindler I.

Hutnik, Wiadomości Hutnicze

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2008

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Vol. 75, nr 8

481-483

EN

The TWIP effect (Twinning Induced Plasticity) is employed in steels with high manganese content to achieve elongation above 60 % and strength of more than 1,200 MPa. Chemical compositions of these steels are varied; with Mn content between 15 and 35 %, sometimes with 2 to 4 % Si or Al and the content of carbon of at least 0.5 to 1.0 wt %. The TWIP effect is based on inducing formation of mechanical twins by introducing strain into the material. Twinning is visible transformation of the crystal structure and the twin boundaries are strong barriers to dislocation gliding [1+3]. The TWIP effect is based on transformation of part of austenite with the face-centered cubic lattice (FCC) into 8 hexagonal martensite and finally into the a martensite with body-centred cubic lattice (BCC) [4]. The phase transformations are dependent on the stacking fault energy. In these steels, this value is about 20 mJ/m2 and strongly depends on alloying elements, mainly Si, Al or Nb [5, 6].

PL

Efekt TWIP (Umocnienie Wywołane Bliźniakówaniem Mechanicznym) stosuje się dla stali z wysoką zawartością manganu w celu osiągnięcia wydłużenia powyżej 60 % i wytrzymałości na rozciąganie powyżej 1200 MPa. Skład chemiczny tych stali jest zróżnicowany; zawartość Mn oscyluje na poziomie 15+35 %, czasami z dodatkiem 2+4 % Si lub Al, natomiast zawartość węgla powinna wynosić co najmniej 0,5+1 %. Efekt TWIP jest oparty na tworzeniu się mechanicznych bliźniaków podczas procesu odkształcania materiału, Bliźniaków anie jest widoczną przemianą struktury krystalicznej, a granice bliźniaków stanowią trwałą barierę dla przemieszczania się dyslokacji [1+3]. TWIP jest efektem przemiany części austenitu o sieci regularnej ściennie centrowanej (SCC), najpierw na e heksagonalny martenzyt, a w końcowej fazie na a martenzyt o sieci regularnej przestrzennie centrowanej (BCC) [4], Etapy tych przekształceń zależą od energii błędów ułożenia. Dla omawianych stali wartość ta wynosiła około 20 mJ/m2 i jest wyraźnie zależna od pierwiastków stopowych, zwłaszcza Si, Al czy Nb [5, 6J.

11

Influence of the heat treatment on the mechanical properties and structure of TWIP steel in wires

Bajor T., Muskalski Z., Wiewiórowska S., Pilarczyk J. W.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 6

337-340

EN

Purpose: The aim of this paper is to determine influence of the drawing process of TWIP steel wires on their mechanical properties and the structure changes. Design/methodology/approach: The heat treatment of steel containing 29.4% manganese and little amount of carbon (0.0049 % C) allows to obtain TWIP effect, and the austenitic structure for this type of steel was realized. In order to investigate the structure changes, the optical microscopy was used. Mechanical properties were determined by the compression test and drawing process. Findings: The analyses of changes of mechanical properties and the structure after particular drawings stages was carried out. At the total draft of 93.4 % the value of drawing stress was 1060MPa, however further deformations of the wire brought relation Rm/R0.2 to be above 1.6. Research limitations/implications: Continuation of the investigations with the use of transmission electron microscopy makes it possible to identify all phases that appear in this steel. Practical implications: Drawn products characterized by high strength properties together with good plasticity might be used for production of connecting elements because they can absorb large quantity of energy. Originality/value: For the first time there were obtained so high hardening level as well as so high plasticity in the drawing process.