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1

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.

2

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.

3

Characteristics of Plasticity of Hot Deformed Cu-Ti Alloys

Szkliniarz A., Blacha L., Szkliniarz W., Łabaj J.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 4

1307--1312

EN

In the paper, results of a study on the effects of deformation conditions (temperature, strain and strain rate) on flow curves, maximum flow stress and corresponding deformation of Cu-Ti alloys with various Ti contents, subjected to hot deformation, are presented. Evaluation of formability of alloys was performed with the use of a Gleeble HDS-V40 thermal-mechanical simulator during uniaxial hot compression at 700 to 900°C, strain rate of 0.1 to 10.0 s-1 and strain of 0 to 1.2 (70%). It was found that within the analysed ranges of temperature, strain rate and strain, Cu-Ti alloys underwent uniform deformation without cracking. The largest deformation resistances were observed for the alloys with the highest Ti contents; their decrease was possible with the temperature raise and the strain rate reduction.

PL

W pracy przedstawiono wyniki badan wpływu warunków odkształcenia (temperatura, wielkosc i predkosc odkształcenia) na przebieg krzywych płyniecia, wartosc maksymalnego naprezenia uplastyczniajacego i odpowiadajacego mu odkształcenia odkształcanych plastycznie na goraco stopów Cu-Ti o zróznicowanej zawartosci Ti. Ocene podatnosci do kształtowania plastycznego stopów przeprowadzono na symulatorze cieplno-mechanicznym systemu Gleeble HDS-V40 w warunkach jednoosiowego sciskania na goraco w zakresie temperatury od 700 do 900°C, predkosci odkształcenia od 0.1 do 10.0 s-1 i odkształcenia od 0 do 1.2 (70%). Stwierdzono, ze w analizowanych przedziałach temperatury, predkosci i wielkosci odkształcenia stopy Cu-Ti odkształcaja sie w sposób jednorodny bez udziału pekania. Wykazano, ze najwieksze opory kształtowania plastycznego towarzysza stopom o najwyzszej zawartosci Ti, a ich zmniejszenie jest mozliwe poprzez podwyzszenie temperatury i obnizenie predkosci odkształcenia.

4

Badania plastyczności i mikrostruktury stopu AZ80 po odkształceniu na gorąco

Kuc D., Bednarczyk I., Niewielski G.

Hutnik, Wiadomości Hutnicze

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2012

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Vol. 79, nr 8

613--619

PL

W artykule przedstawiono wyniki badań wpływu parametrów odkształcenia na strukturę i plastyczność technologiczną stopu AZ80. Strukturę badanego stopu analizowano po jednoosiowym ściskaniu na symulatorze Gleeble. Próby na gorąco przeprowadzono w zakresie temperatury od 250 °C do 400 °C i prędkości odkształcenia 0,01, 0,1, 1 s-1. Uzyskane wyniki pozwoliły na wyznaczenie krzywych płynięcia oraz wskaźników charakteryzujących technologiczną plastyczność.

EN

In the article results of the influence of deformation parameters range structure and plasticity during anneling hot deformation alloy AZ80. Structural examination after annealing and compression test on Gleeble thermo-mechanical simulator. Hot torsion test was performed on torsion plastometer at the temperature range 250÷400 °C and strain rate of 0.01÷1 s-1. The results allowed the determination of flow curves and indices characterizing the technological plasticity.

5

Plasticity of low aluminum alloys from Fe-Al system

Bednarczyk I., Jabłońska M.

Archives of Metallurgy and Materials

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2012

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Vol. 57, iss. 1

271-276

EN

Alloys based on intermetallic phases from the Fe-Al system they belong to a group of high-temperature creep resisting materials of advantageous physicochemical and mechanical properties at an elevated and high temperature. In general, limitation on the capacity for a broad application of intermetals from the Fe-Al system, e.g. as an alternative to expensive alloy steels of specific properties, is their insufficient plasticity, which is a factor inhibiting further their development as constructional materials. The aim of this work is study about the analysis of the influence of hot deformation parameters like a temperature and strain rate on the plasticity and structure changes in alloys on the base Fe-Al system. These alloys are competitive for their cost and properties in comparison with stainless and acid resistance steels. Were analyzed the properties determined in hot compression test of cast alloys Fe-28Al, Fe-28Al-5Cr, contain microelements Mo, Zr, C, B. The tests were carried out on the range of temperature 700°C - 1100°C with strain rate 0,1 s-1. The results indicated that the Cr addition had an positively effect on the plasticity properties. Moreover exhibited that the Cr addition had an influence on the mechanism of the rebuilding the structure changes.

PL

Stopy na osnowie faz międzymetalicznych z układu Fe-Al, zaliczane są do grupy tworzyw żarowytrzymałych, posiadających korzystne właściwości fizykochemiczne i mechaniczne. Zasadniczym problemem ograniczającym ich powszechne stosowanie jest niska plastyczność i skłonność do kruchego pękania co powoduje zahamowanie w dalszym rozwoju jako materiałów konstrukcyjnych. Celem tej pracy jest ocean wpływu parametrów takich jak temperatura, prędkość odkształcenia na plastyczność i zmiany struktury stopów z układu Fe-Al. Ze względu na niski koszt oraz właściwości są konkurencyjne w porównaniu do stali nierdzewnych i kwasoodpornych. Analizowano właściwości w próbie ściskania na gorąco dla odlewniczych stopów Fe-28Al, Fe-28Al-5Cr, zawierających mikrododatki Mo, Zr, C, B. Próby były prowadzone w zakresie temperatury 700 ÷ 1100°C z prędkością odkształcenia 0,1 s-1. Wyniki wskazują, że mikrododatek Cr ma zdecydowany wpływ na właściwości plastyczne. Dodatkowo mikrododatek Cr ma wpływ na zmianę mechanizmu odbudowy struktury.

6

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.

7

Selection of the hot-working conditions for TRIP-type microalloyed steel

Grajcar A.

Archives of Materials Science and Engineering

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2008

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Vol. 31, nr 2

75-78

EN

Purpose: The aim of the paper is to develop hot-working conditions for a low-carbon Mn-Si-Al TRIP-type steel basing on axial compression tests. Design/methodology/approach: The influence of the austenitizing temperature on a grain size of austenite was determined on a basis of the dissolution kinetics in the austenite of MX-type interstitial phases. The identification of processes controlling the strain hardening was carried out in hot-compression tests. Specimens were deformed up to a true strain of 1.0 in a temperature range of 850 to 1150°C with strain rates of 0.1, 1.0 and 10s-¹. The σ-ε curves were useful for developing conditions of multi-stage axial compression. The plastic deformation was realized by the use of the DSI Gleeble 3800 equipment. Findings: It was found that the investigated steel has a fine-grained structure of austenite to a temperature of 1050°C. The obtained σ-ε curves indicate that used plastic deformation conditions influence substantially the εmax strain corresponding to a maximum value of flow stress. It increases with lowering the temperature of plastic deformation. The σ-ε curves obtained during multi-stage compression tests confirmed that under used conditions of temperature and strain a dynamic recovery is a process controlling the strain hardening in a whole strain range. Research limitations/implications: To design in detail hot-rolling conditions, the analysis of the influence of time between successive strains on a fraction of statically recrystallized austenite should be carried out. Practical implications: The obtained σ-ε curves are useful in determining force-energetic parameters of rolling and processes controlling the strain hardening during the hot-rolling. Originality/value: The determined true stress - true strain curves were obtained for the low-carbon TRIP-type steel containing Nb and Ti microadditions.