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1

Tailoring the mechanical properties of hypereutectic in situ Al–Mg2Si composites via hybrid TiB2 reinforcement and hot extrusion

Moazami Mohammad Rasool, Razaghian Ahmad, Mirzadeh Hamed, Emamy Massoud

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e87, 1--9

EN

Microstructure and mechanical properties of Al-15Mg 2 Si-xTiB 2 hybrid composites in the as-cast and wrought conditions were studied. TiB 2 addition led to a significant refinement and modification of primary Mg2Si particles (up to 3 wt% TiB 2 addition) via the heterogeneous nucleation mechanism, which improved the as-cast tensile properties. Further additions led to the appearance of coarse needle-shaped Al 3Ti particles with the consequent deterioration of tensile properties. Hot deformation by extrusion process and elevated-temperature exposure resulted in the fragmentation, dispersion, and spheroidization of pseudo-eutectic Mg 2 Si constituents, which led to a significant enhancement of tensile properties. The ultimate tensile strength of the extruded Al-15Mg 2 Si-3TiB 2 composite was 285 MPa with the total elongation of ~ 8%, which revealed a good strength-ductility balance. The corresponding value for the as-cast Al-15Mg 2 Si composite was only 198 MPa%. Accordingly, this study revealed that the presence of optimum amount of TiB 2 combined with high-temperature thermo-mechanical processing could remarkably improve the mechanical properties of the hypereutectic Al-Mg-Si composites in terms of strength-ductility balance, quality index, and tensile toughness.

2

Experimental investigations of heat generation and microstructure evolution during friction stir processing of SnSbCu alloy

Leszczyńska-Madej Beata, Hrabia-Wiśnios Joanna, Węglowska Aleksandra, Perek-Nowak Małgorzata, Madej Marcin

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e202, 2022

EN

The paper presents the results of experimental investigations of the heat generation and microstructure evolution during the friction stir processing (FSP) of the SnSb11Cu6 alloy. The Triflute tool was used for modification; the process was carried out using two rotational speeds of the tool: 280 and 560 RPM and a constant linear speed of 355 mm/min. Microstructure studies were performed employing the techniques of light microscopy and scanning electron microscopy along with analysis of the chemical composition of micro-areas. Additionally, the phase composition was investigated by means of the X-ray diffraction method, and electron backscatter diffraction (EBSD) analysis and hardness testing were performed before and after FSP modification. Furthermore, measurements of the temperature directly on the modified surface by means of a thermal imaging camera and the temperature in the modified zone with a thermocouple system were performed. It was proved that using FSP to modify the SnSbCu alloy promotes refinement and homogenization of the microstructure, as well as improvement of the hardness. The hardness of the starting material was 24 HB, and after FSP, the hardness increased and amounted to, respectively, 25 and 27 HB after processing at 280 and 560 RPM. The microstructure in the stir zone is formed by the dynamic recrystallization (DRX) process and consists of almost equiaxed tin-rich matrix grains with a size of approx. 5–30 µm and fine particles of Cu6Sn5 and SnSb phases. The temperature distribution in the FSP zone is not uniform and changes in a gradient manner.

3

The Effects of Hot Deformation Parameters on the Size of Dynamically Recrystallized Austenite Grains of HSLA Steel

Gnapowski Sebastian, Opiela Marek, Kalinowska-Ozgowicz Elżbieta, Szulżyk-Cieplak Joanna

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 2

76--84

EN

Materials scientists are seeking to produce metals with reduced weight and dimensions while maintaining the appropriate mechanical properties. There are several ways to improve the internal structure of metals, such as the ultrasound used to solidify liquid metal. The homogeneity of the grains and the uniformity of the metal structure affects its mechanical strength. This paper presents the results of investigations into the effects of hot deformation parameters in compression on the austenite grain size in the HSLA (High Strength Low Alloy) steel (0.16% C, 0.037% Nb, 0.004% Ti, 0.0098% N). The axisymmetric compression investigations were performed on cylindrical investigation specimens using a Gleeble 3800 thermomechanical simulator with the strain rate of 1÷15.9 s-1 and strain degree ε = 1.2. Before deformation, the research specimens were austenitized at TA = 1100÷1250 °C. The metallographic observations of the primary austenite grains were conducted with an optical microscope, while the structure of dynamically recrystallized austenite, inherited by martensite, was examined by using a scanning electron microscope.

4

Investigations on microstructure evolution of TA1 titanium alloy subjected to electromagnetic impact loading

Zhang Xu, Zhu Congcong, Hu Lin, Wu Hequan, Li Chunfeng

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 3

639--647

EN

In this work, the adiabatic shear band of TA1 titanium alloy subjected to electromagnetic impact loading was investigated. The formation of adiabatic shear band and microstructure evolution within it were revealed by microstructure characterizations. Deformation results showed an adiabatic shear band with the width of 10 mm located in shear deformation zone, and most deformations mainly concentrated in the narrow band. The compressive insta-bility and the hardness difference contributed to the formation of adiabatic shear band. Severe shear deformations led to high location density within the adiabatic shear band. A large amount of dislocations distributed in the form of dislocation cells and random dislocations. The rotational dynamic recrystallization mechanism caused that many dy-namic recrystallization grains with the size of 100–200 nm were found inside the adiabatic shear band. Adiabatic temperature rise and distortion energies stored by high dislocation densities provided sub-grain rotations with the driving forces.

5

Wpływ grubości materiału wsadowego i schematu gniotów w procesie walcowania nawrotnego na strukturę i własności mechaniczne blach ze stopu Zn-Cu-Ti

Osuch P., Walkowicz M., Mamala A., Knych T., Pawlicha S., Napióra T., Sokół R.

Rudy i Metale Nieżelazne Recykling

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2017

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R. 62, nr 12

62--67

PL

W artykule przedstawiono wyniki badań wpływu grubości materiału wsadowego w postaci taśmy odlewanej metodą Huntera oraz schematu gniotów jednostkowych w procesie walcowania na strukturę i własności mechaniczne blach ze stopu Zn-Cu-Ti, w szczególności na ich podatność do zginania. W tym celu przeprowadzono eksperyment w warunkach przemysłowych, w którym procesowi walcowania poddano trzy kręgi taśmy o zbliżonym składzie chemicznym o trzech różnych grubościach, wytworzone w procesie odlewania ciągłego metodą Huntera, przy zastosowaniu stałych parametrów ciekłego metalu i stałej prędkości odlewania. Proces walcowania ze względu na różnice w grubości materiału wsadowego, realizowany był z zastosowaniem zróżnicowanych schematów gniotów jednostkowych, i przy ustalonych pozostałych parametrach walcowania, takich jak: temperatura wsadu i prędkość walcowania w poszczególnych przepustach. Próbki wytworzonych w ten sposób blach poddano obserwacjom strukturalnym, na podstawie których stwierdzono zróżnicowany stopień ich rekrystalizacji. Na podstawie analizy otrzymanych wyników badań własności mechanicznych stwierdzono, że stopień dynamicznej rekrystalizacji w procesie walcowania jest ściśle związany z własnościami mechanicznymi gotowych blach, jak i ich podatnością do zginania. Przeprowadzony eksperyment pozwolił wyznaczyć optymalną grubość taśmy odlewanej oraz optymalną ilość gniotów w procesie walcownia, która pozwala na uzyskanie pożądanych własności użytkowych gotowych blach.

EN

The paper presents the results of investigations of the influence of thickness of the input material in the form of the Hunter-cast strip and deformation scheme during rolling process on the structure and mechanical properties of Zn-Cu-Ti alloy sheets, in particular their bendability. For this purpose, an industrial experiment was carried out in which three strips with similar chemical compositions and different thickness, manufactured within Hunter method, were subjected to the rolling process. The rolling process due to the difference in the thickness of the input material was carried out at different deformation schemes and at the constant other rolling parameters, ie rolling temperature and rolling speeds in the following rolling passes. Sheet samples produced in this way were subjected to structural observations, on the basis of which their varying degree of recrystallization was found. Based on the analysis of the obtained results of mechanical tests, it was found that the degree of dynamic recrystallization in the rolling process is closely related to the mechanical properties as well as bendability of the finished sheets. The experiment allowed to determine the optimum thickness of the cast strip and the optimum amount of rolling in the reversing rolling mill process, which allows to achieve the desired properties of the finished sheets.

6

Wpływ temperatury walcowania na strukturę i własności blach ze stopu Zn-Cu-Ti

Osuch P., Walkowicz M., Mamala A., Knych T., Napióra T., Sokół R., Bocheńska S.

Rudy i Metale Nieżelazne Recykling

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2015

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R. 60, nr 10

508--513

PL

W artykule przedstawiono wyniki badań wpływu temperatury nagrzewania wsadu do procesu walcowania taśmy ze stopu Zn-Cu-Ti w walcarce kwarto-nawrotnej na strukturę i własności przetwarzanych blach, w szczególności na ich podatność do zginania. W tym celu przeprowadzono eksperyment w warunkach przemysłowych, w którym procesowi walcowania poddano pięć kręgów taśmy o zbliżonym składzie chemicznym i przy ustalonych podstawowych parametrach walcowania, tj. schemacie gniotów i prędkościach walcowania w poszczególnych przepustach. Próbki wytworzonych w ten sposób blach poddano obserwacjom strukturalnym, na podstawie, których stwierdzono ich różny stopień rekrystalizacji. Na podstawie analizy otrzymanych wyników badań własności mechanicznych stwierdzono, że stopień dynamicznej rekrystalizacji w procesie walcowania jest ściśle związany z własnościami mechanicznymi gotowych blach, jak i ich podatnością do zginania. Przeprowadzony eksperyment pozwolił wyznaczyć minimalną temperaturę nagrzewania odlanego wsadu do procesu walcowania, która pozwala na uzyskanie pożądanych własności użytkowych gotowych blach.

EN

The paper presents the research results on influence of the charge’s heating temperature intended for rolling process of the sheet made from Zn-Cu-Ti alloy in a four-high reversing mill on the structure and properties of the processed sheets, and its susceptibility to bending in particular. To this end, an experiment in industrial conditions was conducted, in which five coils of similar chemical compositions and established basic rolling parameters, which are draft schemes and rolling velocities in particular roll passes, were put to the rolling process. The sheet samples made according to this method were subjected to structural observations, basing on which various fractions of recrystallization were determined. On the grounds of the analysis concerning mechanical properties it was found that the fraction of dynamic recrystallization during the rolling process is tightly connected with mechanical properties and susceptibility to bending of the ready sheets. The performed test allowed to determine the minimal heating temperature of the casted charge designed for rolling process which permits to obtain desirable utilitarian properties of the ready made sheets.

7

Badania odkształcalności wybranych stopów na osnowie faz międzymetalicznych z układu Fe-Al

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

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 8

537--541

PL

W artykule przedstawiono przebieg zmian strukturalnych stopów z układu Fe-Al pod wpływem odkształcenia plastycznego na gorąco. Badania wykonano na plastomerze skrętnym w zakresie temperatury 800°C÷1100°C przy zadanej stałej prędkości odkształcenia 0,1 s-1. Określono badania zmiany mikrostruktury i substruktury badanego stopu przy użyciu techniki mikroskopii świetlnej LM i skaningowo-transmisyjnej mikroskopii elektronowej STEM. Analiza struktury badanych stopów pozwoliła ujawnić zmiany spowodowane dynamicznymi procesami. Otrzymane wyniki badań próby skręcania dla stopu FeAl285Cr wskazują na możliwość uzyskania drobnoziarnistej struktury przy odpowiednio dobranych parametrach procesu (T=1000°C, 1100°C) i dużym odkształceniu ε=40. W temperaturze T=1000°C i 1100°C stwierdzono występowanie efektu nadplastycznego płynięcia.

EN

The paper presents the course of structural changes of alloys from Fe-Al system under the hot plastic deformation with application of a few different temperatures of the process at a constant strain rate value 0,1 s-1. Tests were conducted on torsion plastometer in temperature range from 800°C to 1100°C. The analysis of the microstructure and substructure changes of tested alloy was conducted with using light microscopy LM and scanning-transmission electron microscopy STEM techniques. The analysis of the structure of the alloys allowed to reveal changes caused by dynamic processes of reconstruction of the structure. The results of torsion tests alloy FeAl28Cr5 show the possibility to obtain a fine-grained structure with appropriately chosen parameters of the process (T=1000°C, 1100°C) and a large deformation . Deformation at a temperature of T=1000°C and 1100°C is accompanied by superplastic flow effect.

8

Microstructure evolution after thermo-mechanical treatment of X11MnSiAl25-1-3 TWIP-type steel

Dobrzańska-Danikiewicz A., Borek W., Mazurkiewicz J., Jagiełło A.

Archives of Materials Science and Engineering

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2013

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Vol. 59, nr 1

14--21

EN

Purpose: The purpose of the article is to present the results of research of the effect of thermal and thermoplastic working on the structure of high-manganese austenitic TWIP steels. Design/methodology/approach: Plastometric tests were performed with DSI (Dynamic System Inc.) Gleeble 3800 instrumentation being the equipment of the Scientific and Didactic Laboratory of Nanotechnology and Materials Technologies of the Institute of Engineering Materials and Biomaterials. Changes in the microstructure after individual stages of hot plastic deformation were determined on the basis of detailed microstructure tests with the light microscope and scanning electron microscope. An X-ray phase qualitative analysis of the examined materials in the condition after casting and after thermoplastic working was carried out with the XPert diffractometer by Philips. Findings: It was concluded based on the tests performed that the structure of the examined austenitic high-manganese steel in the initial condition is represented by austenite with numerous annealing twins. The results obtained for investigations in a continuous compression test will enable to establish power and energy parameters and design a hot compression process, consisting of several phases, of axisymmetric specimens, simulating the final rolling passes. Practical implications: By elaborating the detailed data concerning structural changes and power and energy parameters of the thermoplastic working process of the investigated high-manganese austenitic TWIP steel type, it will be possible to design appropriately the final passes of the hot rolling process to obtain an optimum size of grains, which will in turn influence the improved strength properties of the investigated high-manganese austenitic X11MnSiAl25-1-3 steel. Originality/value: The application of thermoplastic working of high-manganese austenitic TWIP steel.

9

Analiza zjawiska rekrystalizacji dynamicznej austenitu w wysokowęglowej stali stopowej za pomocą symulacji ﬁzycznych procesu walcowania

Knapiński M., Dembiczak T., Sawicki S., Garbarz B.

Hutnik, Wiadomości Hutnicze

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2012

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Vol. 79, nr 12

920--923

PL

W artykule przedstawiono wstępne wyniki badań kinetyki rekrystalizacji dynamicznej austenitu stopowego w wysokowęglowej stali. Na podstawie badań eksperymentalnych przeprowadzonych z wykorzystaniem symulatora Gleeble 3800 wyznaczono współczynniki równań konstytutywnych oraz opracowano model matematyczny rekrystalizacji dynamicznej dla badanego gatunku stali. Uzyskane wyniki zostaną wykorzystane do optymalizacji technologii procesu walcowania blach grubych na gorąco z wysokowęglowej stali bainitycznej przeznaczonych na osłony balistyczne.

EN

This paper presents preliminary results of investigation of the kinetics of dynamic recrystallization of alloyed austenite in high carbon steel. On the basis of experimental tests using a Gleeble 3800 simulator constitutive equations and mathematical model of dynamic recrystallization for the investigated steel were determined. The results will be used for the optimization of hot rolling technology of high carbon steel plates used in armour constructions.

10

Hot-working of advanced high-manganese austenitic steels

Dobrzański L. A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 2

507--526

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: The force-energetic parameters of hot-working were determined in continuous and multi-stage compression test performed in temperature range of 850 to 1100°C using the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work-hardening were identified by microstructure observations of the specimens compresses to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopy as well as X-ray diffraction. Findings: The investigated steels are characterized by high values of flow stresses from 230 to 450 MPa. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steels and slightly higher compared to Fe-(15-25)Mn alloys. Increase of flow stress along with decrease of compression temperature is accompanied by translation of εmax strain in the direction of higher deformation. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery and a deciding influence on a gradual microstructure refinement has statical recrystallization. The steel 27Mn-4Si-2Al-Nb-Ti has austenite microstructure with annealing twins and some fraction of ε martensite plates in the initial state. After the grain refinement due to recrystallization, the steel is characterized by uniform structure of γ phase without ε martensite plates. Research limitations/implications: To determine in detail the microstructure evolution during industrial rolling, the hot-working schedule should take into account real number of passes and higher strain rates. Practical implications: The obtained microstructure - hot-working relationships can be useful in the determination of power-force parameters of hot-rolling and to design a rolling schedule for high-manganese steel sheets with fine-grained austenitic structures. Originality/value: The hot-deformation resistance and microstructure evolution in various conditions of hot-working for the new-developed high-manganese austenitic steels were investigated.

11

Characterization of friction stir welds of 6013 and 6013/2017A aluminium alloy sheets

Mroczka K., Dutkiewicz J., Pietras A.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 3

586-589

EN

The results of studies of microstructure and mechanical properties of Wells of 6013 aluminium alloy and welds of 6013 with 2017A alloys are presented. The welds were prepared by a conventional method Friction Stir Welding (FSW). The microstructure of the analyzed welds does not contain any cracks or decohesion. In the centre of the welds of 6013 "onion rings" type of microstucture is observed. Moreover, a clear visible border of recrystallized region was also noticed. Microstructures of a nugget of the weld observed by TEM are characterized by an increased density of dislocations and nanoprecipitates formed at dislocations. The microstructure of the weld of the 6013/2017A alloys is composed of the separate regions of both alloys. Determination of microhardness profiles of the welds revealed hardening of the welds due to ageing. On the contrary, the fracture of the sample ruptured during static tension test shows the working place of a pin-tool and much weaker border of this area.

PL

W artykule przedstawiono wyniki badań mikrostruktury i właściwości mechanicznych zgrzein stopu aluminium 6013 oraz zgrzein stopów aluminium 6013 i 2017A. Zgrzeiny wykonano konwencjonalną metodą Friction Stir Welding (FSW) - zgrzewania tarciowego z mieszaniem materiału zgrzeiny. Mikrostruktura badanych złącz jest ciągła metalurgicznie, bez pięknieć i dekohezji. Analiza mikrostruktury (mikroskopia świetlna) ujawniła w złączu stopu 6013 wyraźną granicę obszaru rekrystalizowanego oraz mikrostrukturę typu onion structure. Mikrostruktura TEM w okolicy jądra badanej zgrzeiny wykazuje podwyższoną gęstość dyslokacji i nanowydzielenia utworzone na dyslokacjach. Mikrostruktura złącza stopów 6013/2017A składa się z odrębnie występujących obszarów obu stopów. Wyznaczenie profili mikrotwardości złącz wykazało umacnianie się materiału w wyniku starzenia. Na powierzchni przełomu próbki po statycznej próbie rozciągania wyraźnie widoczny jest obszar działania trzpienia narzędzia zgrzewającego, co świadczy o zmienionych właściwościach mechanicznych materiału w tym obszarze.

12

Processes forming the microstructure evolution of high-manganese austenitic steel in hot-working conditions

Dobrzański L. A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

397-407

EN

Purpose: The aim of the paper is to characterise the microstructure evolution of new-developed 27Mn-4Si-2Al-Nb-Ti high-manganese steel in various conditions of hot-working. Design/methodology/approach: Flow stresses during the multistage compression test were measured using the Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steel was compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopy as well as X-ray diffraction. Findings: The steel has austenite microstructure with annealing twins and some fraction of ĺ martensite plates in the initial state. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steels and slightly higher compared to Fe-(15-25) Mn alloys. The flow stresses are in the range of 200-400 MPa for the applied conditions of hot-working. Making use of dynamic and metadynamic recrystallization, it is possible to refine the microstructure and to decrease the flow stress to 350 MPa during the last deformation at 850°C. Applying the true strains of 0.23 and 0.19 requires the microstructure refinement by static recrystallization. After the grain refinement due to recrystallization, the steel is characterised by uniform structure of ă phase without ĺ martensite plates. Research limitations/implications: To fully describe the hot-working behaviour of the new-developed steel, further investigations in wider temperature and strain rate ranges are required. Originality/value: The hot-deformation resistance and microstructure evolution in various conditions of hot-working for the new-developed high-manganese 27Mn-4Si-2Al-Nb-Ti austenitic steel were investigated.

13

Modelowanie zmian struktury podczas odkształcania plastycznego na gorąco metodą automatów komórkowych

Kuc D., Gawęd J.

Hutnik, Wiadomości Hutnicze

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2009

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Vol. 76, nr 8

601-603

PL

W artykule przedstawiono model wieloskalowy (CAFE), który opisuje zmiany struktury w warunkach ciągłego odkształcenia oraz umożliwia obliczenie krzywych płynięcia. Do opracowania modelu zmian struktury wykorzystano metodę automatów komórkowych CA. Model zmian naprężenia uplastyczniającego bazuje na średniej gęstości dyslokacji wyznaczonej z siatki CA. Opracowany model zweryfikowano w oparciu o wyznaczone krzywe płynięcia wyznaczone dla stali austenitycznej X3CrNi18-9 i badania struktury z wykorzystaniem mikroskopii świetlnej i zaawansowanych technik mikroskopii elektronowej – transmisyjnej oraz EBSD. Naprężenie uplastyczniające zostało obliczone z wykorzystaniem metody inverse na podstawie danych uzyskanych z prób osiowosymetrycznego ściskania.

EN

The paper is focused on application of multi-scale 2D method. Model approach consists of Cellular Automata (CA) model of microstructure development and the thermal-mechanical finite element (FE) code. Dynamic recrystallization phenomenon is taken into account in 2D CA model which takes advantage of explicit representation of microstructure, including individual grains and grain boundaries. Flow stress is the main material parameter in mechanical part of FE and is calculated on the basis of average dislocation density obtained from CA model. The results attained from the model were validated with the experimental data. In the present study, austenitic steel X3CrNi18-9 was investigated. Light microscopy and EBSD analyses were performed for the initial and final microstructures of the samples. Compression forces were recorded during the tests and flow stresses were determined using inverse method.

14

Modelowanie rekrystalizacji dynamicznej za pomocą dynamicznych sieci neuronowych

Stanisławczyk A., Kusiak J.

Hutnik, Wiadomości Hutnicze

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2009

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Vol. 76, nr 8

659-661

PL

W pracy zaprezentowano neuronowy model naprężenia uplastyczniającego dla mikrostopowej stali z dodatkiem niobu. W modelowaniu wykorzystano dynamiczną sieć neuronową typu LRN (Layer-Recurrent Network). Model uwzględnia dwa kluczowe w procesie rekrystalizacji dynamicznej parametry: temperaturę i prędkość odkształcenia. Opracowany model cechuje się wysoką dokładnością przewidywania wartości naprężenia uplastyczniającego (błąd RMSE równy 3,1 MPa), oraz bardzo dużą szybkością działania. Przedstawione wyniki potwierdzają przydatność dynamicznych sieci neuronowych w modelowaniu zjawisk i procesów dynamicznych.

EN

The paper presents the neural network model of the flow stress for nobium microalloyed steel. The dynamic neural network of the type LRN (Layer-Recurrent Network) was used in modelling. The model takes into account two key parameters in the dynamic recrystallization: temperature and strain rate. The model characterizes high accuracy of flow stress prediction (RMSE equals 3.1 MPa), and the very high speed. Introduced model confirms the usefulness of dynamic neural networks in the dynamic processes modelling.

15

Model zmian naprężenia uplastyczniającego i struktury w warunkach odkształcenia plastycznego na gorąco stali austenitycznej

Kuc D., Pidvysotsky V., Kuziak R.

Hutnik, Wiadomości Hutnicze

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2009

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Vol. 76, nr 8

604-607

PL

W artykule przedstawiono model opisujący krzywe płynięcia, uwzględniający proces rekrystalizacji dynamicznej. Krzywe płynięcia wyznaczono metodą inverse na podstawie próby osiowosymetrycznego ściskania przeprowadzonej na symulatorze Gleeble dla stali austenitycznej X3CrNi18-9. Na podstawie badań opracowano równania opisujące kinetykę rekrystalizacji dynamicznej oraz zmiany wielkości dynamicznie zrekrystalizowanego ziarna badanej stali. Uzyskano dobrą zgodność krzywych płynięcia obliczonych na podstawie modelu reologicznego z danymi uzyskanymi w warunkach eksperymentalnych.

EN

This paper describe model of flow curves provide for dynamic recrystallization process. Flow curves was developed by inverse method during axial-symmetric compression test with using Gleeble simulator for austenitic steel X3CrNi18-9 grade. Formulas, which describe kinetics of dynamic recrystallization and changes of dynamic recrystallized grain size of tested steel were developed. Good compatibility between flow curves of a rheological model with data known of research was obtain.

16

Microstructure evolution of high-manganese steel during the thermomechanical processing

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

Archives of Materials Science and Engineering

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2009

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Vol. 37, nr 2

69-76

EN

Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution of new-developed high-manganese austenitic steel. Design/methodology/approach: The hot-working behaviour was determined in continuous and multi-stage compression tests performed in a temperature range of 850 to 1100°C by the use of the Gleeble 3800 thermomechanical simulator. The processes controlling work hardening and removing it were identified by microstructure evolution observations in successive stages of compression with the amount of true strain 4x0.29, 4x0.23 or 4x0.19. Findings: The investigated steel is characterized by high values of flow stresses from 250 to 450 MPa. Increase of flow stress along with decrease of compression temperature is accompanied by translation of εmax strain in the direction of higher deformation. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery and a deciding influence on a gradual microstructure refinement has statical recrystallization. Research limitations/implications: To determine in detail the microstructure evolution during industrial rolling, the hot-working schedule should take into account real number of passes and higher strain rates. Practical implications: The obtained σ-ε curves can be useful in determination of power-force parameters of hot-rolling and to design a rolling schedule ensuring a fine-grained microstructure of high-manganese steel products. Originality/value: The microstructure evolution in various conditions of hot-working for the new-developed high-manganese Mn-Si-Al-Nb steel was determined.

17

Zmiany struktury ferrytycznej stali odpornej na korozję podczas odkształcania plastycznego na ciepło

Samolczyk J., Kachlicki T.

Obróbka Plastyczna Metali

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2008

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T. 19, nr 1

57-64

PL

W artykule omówiono wyniki badań strukturalnych stali X3CrTi17 po obróbce plastycznej na ciepło. Zależność wielkości naprężeń uplastyczniających od temperatury odkształcania stali X3CrTi17 wyznaczono podczas spęczania próbek Rastiegajewa. Zaobserwowano, że podczas odkształcania plastycznego w badanych materiałach zachodzą procesy dynamicznej odbudowy struktury. Otrzymane wyniki pozwalają skutecznie przewidywać końcową strukturę i właściwości wyrobów ze stali typu X3CrTi17, odpornej na korozję, po obróbce plastycznej na ciepło.

EN

The dependence of the yield stress on the temperature of X3CrTi17 steel deformation has been determined while upsetting Rastegaev samples. It has been found that during plastic deformation, processes of dynamic structure rebuilding take place in the examined materials. The results obtained allow to forsee the final structure and properties of products made of X3CrTi17 type steels resistant to corrosion after warm forming.

18

Structural and mechanical behaviour of TRIP-type microalloyed steel in hot-working conditions

Grajcar A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 30, nr 1

27-34

EN

Purpose: The aim of the paper is to investigate the influence of various deformation conditions on microstructure evolution and flow curves of TRIP-type steel. Design/methodology/approach: In order to determine the influence of MX-type interstitial phases on limiting the grain growth of primary austenite, samples were quenched in water from a temperature range, from 900 to 1200*C. Determination of processes controlling strain hardening was carried out in compression test using Gleeble 3800 simulator. The σ-ε curves were defined in a temperature range from 850 to 1150*C, for 0.1, 1 and 10s -1 of strain rate. To determine the progress of recrystallization samples were isothermally held for up to 60 s at 900 and 1000*C. Findings: Profitable impact of TiN and NbC particles on austenite grain growth limitation is present up to 1050*C. The values of flow stress are equal from 120 to 270 MPa. The steel is characterized by quite high values of deformation, εmax=0.4-0.65, corresponding to maximum stress on σ-ε curves. Beneficial grain refinement of primary austenite microstructure can be obtained due to static recrystallization. In temperature of 1000*C, t0.5 is equal 35 s and elongates to 43 s after decreasing deformation temperature to 900*C. The σ-ε curves obtained during multi-stage compression tests confirmed that a process controlling the strain hardening is a dynamical recovery. Research limitations/implications: To design hot-rolling conditions, the analysis of the primary austenite microstructure evolution during successive deformation cycles should be carried out. Practical implications: The obtained precipitation kinetics of MX-type phases and σ-ε curves are useful in determining hot-rolling conditions ensuring the fine-grained microstructure of primary austenite. Originality/value: The determined true stress-true strain curves were obtained for the TRIP-type microalloyed steel containing decreased Si concentration.

19

Influence of hot-working conditions on a structure of high-manganese austenitic steels

Dobrzański L., Grajcar A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 29, nr 2

139-142

EN

Purpose: The aim of the paper is to determine the influence of hot deformation conditions on σ - ε curves and structure changes of new-developed high-manganese austenitic steels. Design/methodology/approach: The force-energetic parameters of hot-working were determined in hot-compression tests performed in a temperature range of 850 to 1050° C by the use of the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work hardening at 850° C were identified by microstructure observations of the specimens water-quenched after plastic deformation to a true strain equal 0.22, 0.51 and 0.92. Findings: At initial state the steel containing 3% of Si and Al possesses homogeneous austenite structure with many annealing twins. Increased up to 4% Si concentration and decreased to 2% Al concentration result in a presence of some fraction of ε martensite plates. For applied deformation conditions, the values of flow stress vary from 250 to 450MPa - increasing with decreasing deformation temperature. A relatively small values of ε max deformation at temperatures of 1050 and 950° C allow to suppose that in this range of temperature, to form a fine-grained microstructure of steels, dynamic recrystallization can be used. At a temperature of 850° C, the dynamic recrystallization leads to structure refinement after true strain of about 0.51. Research limitations/implications: To determine in detail the hot-working behaviour of developed steels, a progress of recrystallization as a function of time at deformation temperature should be investigated. Practical implications: The obtained stress-strain curves can be useful in determination of power-force parameters of hot-rolling of high-manganese austenitic steels. Originality/value: The hot-working behaviour of new-devoloped high-manganese austenitic steels containing Nb and Ti microadditions was investigated.

20

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.