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1

Influence hot plastic deformation on the structure and properties of carbon steel of the railway wheel

Vakulenko Igor, Plitchenko Sergey, Bolotova Dariy, Asgarov Khangardash

Zeszyty Naukowe. Transport / Politechnika Śląska

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2023

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z. 121

257--266

EN

The study is devoted to the explanation of the influence of hot plastic deformation on the properties of railway wheels. The shape of individual elements of the wheel provides for a different degree of hot compression, which determines the mechanism for the development of the recrystallization at austenite. With a decrease in the degree of the hot deformation, a certain proportion of grains with a low energy of linear stretching are formed in austenite. As a result, of the low mobility of such boundaries, the likelihood of preservation of part of the substructural state of the austenite increases, which should affect the formation of a colony of perlite during the cooling of the carbon steel. Against background preservation and a dependence of strength properties on the dispersion of the pearlite colony, the appearance in austenite of grain boundaries with a low energy of linear tension leads to a qualitative change in the plastic properties of railway wheel steel. The increase in plasticity of carbon steel with an increase in dispersion of the pearlite colony is due to a decrease in the effect of solid solution hardening and an increase in the role of the ferrite-cementite interface in the development processes of strain hardening carbon steel. The results obtained can be useful for improving the technology of manufacturing all-rolled railway wheels.

2

Effect of hot deformation and isothermal holding temperature on retained austenite characteristics in 3-5% Mn multiphase steels

Opiela Marek, Grajcar Adam, Pakieła Wojciech

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 2

art. no. e144611

EN

The paper presents stress-strain characteristics recorded during the four-step compression of axisymmetric samples in the Gleeble thermomechanical simulator. The hot deformability of three steels with Mn concentrations of 3%, 4% and 5% was compared. The analysis of the influence of plastic deformation and Mn content on the microstructure of alloys, and in particular, on a fraction and morphological features of the retained austenite, was performed. The proportion of the retained austenite was determined by the X-ray diffraction method. It was found that the content of Mn in the range from 3% to 5% does not have a significant impact on the high-temperature resistance of the steel during compression tests, but it has a significant influence on the microstructure of the steel and the fraction of retained austenite. The optimal conditions for maximizing the proportion of retained austenite were obtained at the temperature of 400 °C, and it decreased with increasing Mn concentration in the steel. It has been shown that it is related to the redistribution of carbon from the remaining austenite fraction with an increase in the manganese content. The mechanical properties were determined on the basis of hardness measurements.

3

Modelling of Plastic Flow Behaviour of Metals in the Hot Deformation Process Using Artificial Intelligence Methods

Mrzygłód Barbara, Łukaszek-Sołek Aneta, Olejarczyk-Wożeńska Izabela, Pasierbiewicz Karolina

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 3

41--52

EN

Hot deformation of metals is a widely used process to produce end products with the desired geometry and required mechanical properties. To properly design the hot forming process, it is necessary to examine how the tested material behaves during hot deformation. Model studies carried out to characterize the behaviour of materials in the hot deformation process can be roughly divided into physical and mathematical simulation techniques. The methodology proposed in this study highlights the possibility of creating rheological models for selected materials using methods of artificial intelligence, such as neuro-fuzzy systems. The main goal of the study is to examine the selected method of artificial intelligence to know how far it is possible to use this method in the development of a predictive model describing the flow of metals in the process of hot deformation. The test material was Inconel 718 alloy, which belongs to the family of austenitic nickel-based superalloys characterized by exceptionally high mechanical properties, physicochemical properties and creep resistance. This alloy is hardly deformable and requires proper understanding of the constitutive behaviour of the material under process conditions to directly enable the optimization of deformability and, indirectly, the development of effective shaping technologies that can guarantee obtaining products with the required microstructure and desired final mechanical properties. To be able to predict the behaviour of the material under non-experimentally tested conditions, a rheological model was developed using the selected method of artificial intelligence, i.e. the Adaptive Neuro-Fuzzy Inference System (ANFIS). The source data used in these studies comes from a material experiment involving compression of the tested alloy on a Gleeble 3800 thermo-mechanical simulator at temperatures of 900, 1000, 1050, 1100, 1150oC with the strain rates of 0.01 - 100 s-1 to a constant true strain value of 0.9. To assess the ability of the developed model to describe the behaviour of the examined alloy during hot deformation, the values of yield stress determined by the developed model (ANFIS) were compared with the results obtained experimentally. The obtained results may also support the numerical modelling of stress-strain curves.

4

Study on Dynamic Recrystallization Models of 21-4N Heat Resistant Steel

Li Yiming, Huang Xiaomin, Ji Hongchao, Li Yaogang, Wang Baoyu, Tang Xuefeng

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

145--152

EN

The high-temperature deformation process and dynamic recrystallization (DRX) process of 21-4N were investigated under the conditions of the deformation temperature range of 1273~1453K, the strain rate range of 0.01~10s-1 and the deformation degree of 60% (the total deformation is 0.916) by using Gleeble-1500D thermal simulated test machine. The curves of stress-strain (σ – ε) were obtained, and the curves of work hardening rate (θ) and strain (ε) were obtained by taking derivative of σ – ε. The DRX critical strains under different conditions were determined by the curves of work hardening rate (θ – ε), and the DRX critical strain model was established. The peak strains of 21-4N were obtained by the curves of σ – ε, the relationship between peak stress (σp) and critical strain (εc) was determined, and the peak strain model was established. The DRX volume fraction models of 21-4N were established by using Avrami equation. The DRX grain size of 21-4N was calculated by Image Pro Plus 6.0, and its DRX grain size models were established.

5

Enhanced tensile properties of as-cast Mg-10Al magnesium alloy via strontium addition and hot working

Ghorbani Fereshte, Emamy Massoud, Mirzadeh Hamed

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

752--760

EN

The lightweight magnesium–aluminum alloys are extensively used in automotive and aerospace industries due to their high-specific strength and low alloying cost, Grain refining via alloying and hot deformation is known as a viable technique for the enhancement of mechanical properties of these alloys. Accordingly, in the present work, grain size refinement and improvement of tensile properties of Mg-10Al magnesium alloy ingot via strontium addition (up to 1 wt%) and hot working (extrusion process) were studied. It was revealed that the addition of Sr up to 0.05 wt% leads to grain refinement of Mg-Al-Sr alloys with the resulting best strength-ductility combination. The as-cast alloys were quite brittle with total elongations well below 5% and their ultimate tensile strength (UTS) values were below 200 MPa, which was attributed to the coarse as-cast structure with a high content of brittle intergranular β-Mg17Al12 phase. It was also found that the aspect ratio of the Al4Sr particles increases by increasing strontium content, which contributes to the deterioration of tensile properties at high strontium contents. Homogenization treatment at elevated temperatures led to the dissolution of the β phase, while the thermally stable Al4Sr particles remained undissolved. The extruded alloys showed remarkably higher strength and ductility compared to the as-cast ingots, which were related to the remarkable grain refinement induced by the recrystallization processes during the hot extrusion process, the disappearance of the deleterious network of the intergranular eutectic constituent, and providing high solute Al content. As a result, UTS of ~ 406 MPa and total elongation of ~ 24% were obtained for the extruded alloy with 0.05 wt% Sr.

6

Effect of Powder Size on the Microstructure and Magnetic Properties of Nd-Fe-B Magnet Alloy

Cho Ju-Young, Abbas Sardar Farhat, Choa Yong-Ho, Kim Taek-Soo

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

623--626

EN

Rare earth Nd-Fe-B, a widely used magnet composition, was synthesized in a shape of powders using gas atomization, a rapid solidification based process. The microstructure and properties were investigated in accordance with solidification rate and densification. Detailed microstructural characterization was performed by using scanning electron microscope (SEM) and the structural properties were measured by using X-ray diffraction. Iron in the form of α-Fe phase was observed in powder of about 30 μm. It was expected that fraction of Nd2 Fe14 B phase increased rapidly with decrease in powder size, on the other hand that of α-Fe phase was decreased. Nd-rich phase diffused from grain boundary to particle boundary after hot deformation due to capillary action. The coercivity of the alloy decreased with increase in powder size. After hot deformation, Nd2 Fe14 B phase tend to align to c-axis.

7

Combined effects of strain and cooling path on hot deformation response and microstructure of low-carbon structural steel

Morawiec M., Borek W., Mroziński M., Grajcar A.

Archives of Materials Science and Engineering

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2019

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Vol. 95, nr 1

5--11

EN

Purpose: The aim of the paper is to analyse the effect of thermomechanical process with different cooling paths on microstructure and mechanical properties of low-carbon structural steel. Design/methodology/approach: The steel used for the investigation was subjected to two step deformation using a Gleeble 3800 simulator and then held at designed temperatures from 650ºC to 800ºC for different times. A final step included water cooling to room temperature to freeze the microstructure. Typical microscopic studies have been done. The analysis of the volume fraction of presented phases was carried out together with the measurement of grain size by means of image analysis. The last part of conducted research was hardness analysis of the steel after the different heat treatments. Findings: It was found that the microstructure constitution and grain size are strongly dependent on the temperature of isothermal holdings. The microstructure of steel held at 800ºC is composed of the mixture of bainite and two kinds of ferrite: globular and acicular. When the temperature was lowered by 50ºC the ferrite shows the globular morphology. When the temperature drops to 700ºC and below it, the microstructure is composed of ferritic-pearlitic mixture. It was observed that when the isothermal temperature was increased the grain size decreased and the opposite effect was observed for the holding time. The longer the time of the isothermal holding, the larger was the grain size. Research limitations/implications: For better understanding of the phase transformation kinetics in this steel the dilatometric test are planned. Practical implications: The knowledge of the microstructure evolution and hot deformation response of low-carbon structural steels is important from the industrial point of view. Originality/value: The combined effects of hot deformation and different cooling paths give the useful information on a microstructure evolution.

8

Wysokowytrzymałe niskostopowe stale na odkuwki matrycowe chłodzone w sposób regulowany bezpośrednio po kuciu

Garbarz B., Żak A., Walnik B., Zalecki W.

Prace Instytutu Metalurgii Żelaza

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2017

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T. 69, nr 4

19--33

PL

Artykuł zawiera wyniki badań eksperymentalnych, których celem był dobór składu chemicznego stali i opracowanie parametrów chłodzenia bezpośrednio po kuciu, zapewniających uzyskanie wysokiej wytrzymałości oraz dobrej plastyczności i udarności odkuwek matrycowych o średnicy /grubości do ok. 50 mm. Eksperymentalne stale poddano badaniom hartowności, opracowano diagramy przemian fazowych CTPc, wykonano symulacje obróbek cieplnoplastycznych, przeprowadzono badania mikro-strukturalne i dla wybranych wariantów obróbki zmierzono właściwości mechaniczne. Wykazano, że uzyskanie wysokiej udarności KVCharpyV/+20℃ na poziomie 170 J przy wytrzymałości powyżej 1000 MPa umożliwia stal zawierająca 0,1%C, 1,8%Mn, 0,4%Cr, o strukturze bainityczno-martenzytycznej składającej się z ok. 70% bainitu i ok. 30% martenzytu listwowego. Otrzymanie bardzo wysokiej wytrzymałości powyżej 1400 MPa i udarności KVCharpyV/+20℃ minimum 60 J jest możliwe dla stali zawierającej 0,2%C, 1,5%Mn, 0,4%Cr, 0,3%Mo, o mikrostrukturze martenzytyczno-bainitycznej składającej się z 50% lub nieco większej ilości martenzytu listwowego i 50% lub nieco mniejszej ilości bainitu.

EN

The paper presents results of experimental investigation aimed at selection of chemical composition of steel and development of parameters of cooling directly after forging allowing to obtain high strength and good plasticity and impact toughness of closed die forgings with diameter/thickness up to 50 mm. The experimental steels were characterised by assessment of the hardenability, developing of CCT phase diagrams, the effects of thermomechanical treatments and - for chosen variants - measurements of mechanical properties and description of microstructure. It was shown that high impact toughness KVCharpyV/+20℃ at the level of 170 J and strength over 1000 MPa are possible to obtain for steel containing 0.1%C, 1.8%Mn, 0.4%Cr, with bainitic-martensitic microstructure comprising ca 70% of bainite and ca 30% of lath martensite. A very high strength over 1400 MPa and impact toughness KVCharpyV/+20℃ minimum of 60 J can be obtained for steel containing 0.2%C, 1.5%Mn, 0.4%Cr, 0.3%Mo, with martensitic-bainitic microstructure comprising 50% or some more of lath martensite and 50% or little less of bainite.

9

Wpływ parametrów odkształcenia na gorąco na mikrostrukturę i właściwości plastyczne stopu magnezu AZ31

Hadasik E., Kuc D., Bednarczyk I.

Hutnik, Wiadomości Hutnicze

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2017

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Vol. 84, nr 8

306--309

PL

W artykule przedstawiono wpływ parametrów odkształcenia na technologiczną plastyczność i mikrostrukturę stopu AZ31. Wykonano próby ciągłego, dwustopniowego oraz wielostopniowego odkształcenia na gorąco w celu analizy wpływu parametrów tj. temperatura nagrzewania, wielkość odkształcenia, prędkość odkształcenia oraz czas wytrzymania po odkształceniu na mikrostrukturę i plastyczność badanego stopu.

EN

The article is presented the effect of deformation parameters on the plasticity and microstructure of alloy AZ31. Continuous, two-stage and multi-stage hot deformation tests were performed to analyze the effect of parameters such as heating temperature, deformation size, deformation speed and deformation time after deformation on the alloy microstructure and plasticity of the alloy.

10

Charakterystyka odkształcalności nadstopu Ni-Fe podczas odkształcania plastycznego na gorąco

Ducki K. J., Mendala J.

Hutnik, Wiadomości Hutnicze

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2017

|

Vol. 84, nr 8

301--305

PL

W pracy przedstawiono wpływ dwóch wariantów wstępnego wygrzewania 1120°C/2h i 1180°C/2h oraz parametrów odkształcania plastycznego na gorąco na właściwości plastyczne nadstopu IN-718. Badania odkształcalności stopu wykonano metodą skręcania na gorąco na plastomerze skrętnym. Próbki skręcano do zerwania w zakresie temperatury 900−1150°C ze stałą prędkością odkształcania 0,1 i 1,0 s-1. Na wyznaczonych i skorygowanych krzywych płynięcia określono wskaźniki charakteryzujące właściwości plastyczne stopu oraz analizowano zależności temperaturowe maksymalnego naprężenia uplastyczniającego (σpp) i odkształcenia granicznego (εf). Stwierdzono, że optymalne wartości maksymalnego naprężenia uplastyczniającego i odkształcenia granicznego uzyskano dla stopu po wstępnym wygrzewaniu 1120°C/2h i odkształcaniu z prędkością 0,1 s-1 w zakresie temperatury 1050−1100°C. Zależności pomiędzy maksymalnym naprężeniem uplastyczniającym i parametrem Zenera-Hollomona (Z) przedstawiono w postaci funkcji potęgowej σpp = A×Zn. Wartości energii aktywacji odkształcania na gorąco (Q) wyznaczono dla dwóch wariantów wstępnego wygrzewania stopu, tj. 1120°C/2h i 1180°C/2h i wyniosły − odpowiednio − 478 kJ/ mol i 628 kJ/mol.

EN

The influence of two variants of initial soaking at 1120°C/2h and 1180°C/2h and parameters of hot plastic working on the deformability of an IN-718 type superalloy have been presented. The hot deformation characteristics of alloy were investigated by hot torsion tests. The tests were executed at constant strain rates of 0.1 and 1.0 s-1, and testing temperature in the range of 900°C to 1150°C and were conducted until total fracture of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of maximum yield stress (σpp) and strain limit (εf). It was found that optimal values of flow stress and strain limit were obtained for the alloy after its initial soaking at 1120°C/2h and deformation in the temperature range of 1050-1100 °C at strain rate 0.1 s-1.The relationship between the maximum yield stress and the Zener-Hollomon parameter (Z) was described by σpp = A×Zn power function. Activation energy for hot working (Q) was assessed for the alloy after two variants of initial soaking, i.e. 1120°C/2h and 1180°C/2h and amounted − respectively − 478 kJ/mol and 628 kJ/mol.

11

The characteristic of deformability and quantitative description of the microstructure of hot-deformed Ni-Fe superalloy

Ducki K. J., Rodak K., Mendala J., Wojtynek L.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 1

297--302

EN

The paper presents the results of research concerning the influence of hot plastic working parameters on the deformability and microstructure of a Ni-Fe superalloy. The research was performed on a torsion plastometer in the range of temperatures of 900-1150°C, at a strain rates 0.1 and 1.0 s-1. Plastic properties of the alloy were characterized by the worked out flow curves and the temperature relationships of flow stress and strain limit. The structural inspections were performed on microsections taken from plastometric samples after so-called “freezing”. The stereological parameters as the recrystallized grain size, inhomogenity and grain shape have been determined. Functional relations between the Zener-Hollomon parameter and the maximum yield stress and the average grain area have been developed and the activation energy for hot working has been estimated.

12

Mechanical and Microstructural Response of Near Beta Ti Alloys to Hot Tensile Testing

Abbasi S. M., Momeni A., Daraee M., Akhondzadeh A., Mirsaeed S. G.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2A

815--823

EN

Hot tensile tests were carried out on Timetal-125 and Timetal-LCB near beta Ti alloys at temperatures in range of 600-1000°C and constant strain rate of 0.1 s-1. At temperatures below 700-800°C, the homogenuous and total strains for Timetal-LCB were greater than those for Timetal-125. In contrast, at temperatures over 800°C, Timetal-125 showed better hot ductility. The yield point phenomena was observed in Timetal-LCB at all temperatures. Unlikely, for Timetal-125, it was observed only at temperatures over 800°C. The weaker yield point phenomena in Timetal-125 could be attributed to the negative effect of Al on the diffusion of V. At all temperatures Timetal-LCB exhibited higher strength than Timetal-125. It was found that there should be a direct relationship between the extent of yield point phenomena and strength and dynamic softening through hot tensile testing. It was observed that at temperatures beyond 800°C (beta phase field in both alloys) dynamic recrystallization can progress more in Timetal-125 than in Timetal-LCB. These results were in good agreement with the better hot ductility of Timetal-125 at high temperatures. At low temperatures, i.e. below 700-800°C, partial dynamic recrystallization occurs in beta and dynamic globularization in alpha phase. These processes progress more in Timetal-LCB than in Timetal-125.

13

Hot deformation behavior of Mg-Zn-Al alloy tube processed by severe plastic deformation

Fata A., Faraji G., Mashhadi M. M., Tavakkoli V.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 1

159--166

EN

In the current study, severe plastic deformation (SPD) was applied on a commercial Mg-3Al-1Zn alloy tubes via parallel tubular channel angular pressing (PTCAP) route. Different passes of PTCAP process were applied, and microstructure, hardness and tensile properties at the room, and elevated temperatures were evaluated. The results showed that bimodal microstructure appeared and led to AZ31 alloy represented higher hardness, higher strength with a reasonable elongation at room temperature. Similarly, very high elongation to failure was achieved at a higher temperature. The increase in the number of SPD passes up to two, leads to increasing the ductility up to 263% at 400°C. Then, an increase in the number of PTCAP passes to three, leads to decrease in the ductility as the results of formation of microvoids when SPD processing at higher equivalent strains without a sufficient hydrostatic compressive stress. Relatively ductile fracture mode was also occurred in all samples.

14

The characteristic of deformability of Fe–Ni superalloy during high-temperature deformation

Ducki K. J.

Inżynieria Materiałowa

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2016

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Vol. 37, nr 1

29--34

EN

The influence of two variants of initial soaking at 1100°C/2 h and 1150°C/2 h and parameters of hot plastic deformation on the deformability of Fe–Ni superalloy have been presented. The hot deformation characteristics of alloy were investigated by hot torsion tests using Setaram torsion plastometer. The tests were executed at constant strain rates of 0.1 and 1.0 s–1, and testing temperature in the range of 900 to 1150°C and were conducted until total fracture of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of maximum yield stresses (σpp) and strain limits (εf). The flow stress of the torsion tests showed a single peak in the flow stress-strain curves, and indicated that a dynamic recovery and recrystallization took place during the hot deformation. It was found that optimal values of flow stresses and strain limits were obtained for the alloy after its initial soaking at 1100°C/2 h and deformation in the temperature range of 1050÷950°C at strain rate 0.1 s–1. The increase of maximum yield stresses, σpp, and decrease of strain limit of the alloy, εf, as the initial soaking temperature was rising up to 1150°C/2 h, with the strain rate increasing to 1.0 s–1, was associated with a growth of the initial grain size and the degree of austenite saturation with alloying elements. The relationship between the maximum yield stresses and the Zener-Hollomon parameter (Z) was described by σpp = A × Zn power function. Activation energy for hot working (Q) was assessed for the alloy after two variants of initial soaking, i.e. 1100°C/2 h and 1150°C/2 h and amounted, respectively, 442 kJ/mol and 519 kJ/mol.

PL

Żarowytrzymałe nadstopy Fe–Ni umacniane wydzieleniowo fazą typu γ′-Ni3(Al, Ti) są stopami trudno odkształcalnymi i mają duże wartości naprężenia uplastyczniającego w wysokiej temperaturze. W doborze warunków przeróbki plastycznej na gorąco stopów Fe–Ni należy uwzględniać: rozmiar ziarna osnowy, parametry odkształcania plastycznego oraz przebieg rekrystalizacji. W pracy podjęto badania nad wpływem warunków wstępnego wygrzewania oraz parametrów odkształcania plastycznego na gorąco na odkształcalność technologiczną wybranego nadstopu Fe–Ni. Celem prowadzonych badań był dobór warunków wstępnego wygrzewania oraz określenie nakorzystniejszych parametrów kształtowania plastycznego na gorąco wyrobów ze stopów Fe–Ni.

15

Study of flow softening mechanisms of a nickel-based superalloy with o phase

Lin Y. C., He D.-G, Chen M. S., Chen X.-M., Zhao C.-Y., Ma X.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 3

1537--1546

EN

The flow softening behaviors of a nickel-based superalloy with o phase are investigated by hot compression tests over wide ranges of deformation temperature and strain rate. Electron backscattered diffraction (EBSD). optical microscopy (OM), and scanning electron microscopy (SEM) are employed to study the flow softening mechanisms of the studied superalloy. It is found that the flow softening behaviors of the studied superalloy are sensitive to deformation temperature and strain rate. At high strain rate and low deformation temperature, the obvious flow softening behaviors occur. With the increase of deformation temperature or decrease of strain rate, the flow softening degree becomes weaken. At high strain rate (1s-1), the flow softening is mostly induced by the plastic deformation heating and flow localization. However, at low strain rate domains (0.001-0.01s-1), the effects of deformation heating on flow softening are slight. Moreover, the flow softening at low strain rates is mainly induced by the discontinuous dynamic recrystallization and the dissolution of 6 phase (Ni3Nb).

16

Microstructure of Hot-Deformed Cu-3Ti Alloy

Szkliniarz A., Szkliniarz W., Blacha L., Siwiec G.

Archives of Metallurgy and Materials

|

2016

|

Vol. 61, iss. 1

347--352

EN

In the paper, results of investigations regarding temperature and strain rate effects on hot-deformed Cu-3Ti alloy microstructure are presented. Evaluation of the alloy microstructure was performed with the use of a Gleeble HDS-V40 thermal-mechanical simulator on samples subjected to uniaxial hot compression within 700 to 900ºC and at the strain rate of 0.1, 1.0 or 10.0 s-1 until 70% (1.2) strain. It was found that within the analyzed temperature and strain rate ranges, the alloy deformation led to partial or complete recrystallization of its structure and to multiple refinement of the initial grains. The recrystallization level and the average diameter of recrystallized grains increase with growing temperature and strain rate. It was shown that entirely recrystallized, fine-grained alloy structure could be obtained following deformation at the strain rate of min 10.0 s-1 and the temperature of 800°C or higher.

17

Charakterystyka odkształcalności nadstopu Fe-Ni podczas odkształcania plastycznego na gorąco

Ducki K. J.

Hutnik, Wiadomości Hutnicze

|

2015

|

Vol. 82, nr 8

520--526

PL

W pracy przedstawiono wyniki badań wpływu wstępnego wygrzewania i parametrów odkształcania plastycznego na gorąco na charakterystyki odkształcalności nadstopu Fe-Ni. Badania odkształcalności stopu wykonano metodą skręcania na gorąco na plastomerze skrętnym. Próbki skręcano do zerwania w zakresie temperatury 900÷1150°C ze stałą prędkością odkształcania 0,1 i 1,0 s-1. Na wyznaczonych i skorygowanych krzywych płynięcia określono wskaźniki charakteryzujące właściwości plastyczne stopu oraz analizowano zależności temperaturowe maksymalnego naprężenia uplastyczniającego (σpp) i odkształcenia granicznego (εf). Opracowane krzywe płynięcia plastycznego stopu wykazują pojedyncze maksimum naprężenia uplastyczniającego, co świadczy o przebiegu procesów zdrowienia i rekrystalizacji dynamicznej podczas odkształcania na gorąco. Zależności pomiędzy maksymalnym naprężeniem uplastyczniającym i parametrem Zenera-Hollomona (Z) przedstawiono w postaci funkcji potęgowej σpp = A × Zn. Wyznaczone wartości energii aktywacji procesu odkształcania plastycznego na gorąco (Q) dla dwóch wariantów wstępnego wygrzewania stopu, tj. 1100°C/2h i 1150°C/2h wyniosły odpowiednio 442 kJ/mol i 519 kJ/mol.

EN

The influence of initial soaking and parameters of plastic deformation on the deformability of Fe-Ni superalloy have been presented. The hot deformation characteristics of alloy were investigated by hot torsion tests using of torsional plastometer. The tests were executed at constant strain rates of 0.1 and 1.0 s-1, and testing temperature in the range of 900 to 1150°C and were conducted until total fracture of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of flow stresses (σpp) and strain limits (εf). The flow stress of the torsion tests showed a single peak in the flow stress-strain curves, and indicated that a recovery and dynamic recrystallization took place during the hot deformation. The relationship between the peak stresses and the Zener-Hollomon parameter (Z) were described by σpp = A × Zn power function. Activation energy for hot working (Q) was assessed for the alloy after two variants of previous heating, i.e. 1100°C/2h and 1150°C/2h and amounted respectively 442 kJ/mol and 519 kJ/mol.

18

Hot Deformation Of 6xxx Series Aluminium Alloys

Mrówka-Nowotnik G., Sieniawski J., Kotowski S., Nowotnik A., Motyka M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

1079--1084

EN

The hot deformation behavior of the 6xxx aluminum alloys was investigated by compression tests in the temperature range 100°C-375°C and strain rate range 10−4s−1 and 4×10−4s−1 using dilatometer DIL 805 BÄHR Thermoanalyse equipped with accessory attachment deformation allows the process to execute thermoplastic in vacuum and inert gas atmosphere. Associated microstructural changes of characteristic states of examined alloys were studied by using the transmission electron microscope (TEM). The results show that the stress level decreases with increasing deformation temperature and deformation rate. And was also found that the activation energy Q strongly depends on both, the temperature and rate of deformation. The results of TEM observation showing that the dynamic flow softening is mainly as the result of dynamic recovery and recrystallization of 6xxx aluminium alloys.

PL

Obróbkę cieplno-plastyczną stopów aluminium grupy 6xxx prowadzono w zakresie temperatury 100°C-375°C i prędkości odkształcania 10−4s−1 i 4×10−4s−1 na dylatometrze DIL 805 BÄHR Thermoanalyse wyposażonym w przystawkę odkształceniową umożliwiającą wykonanie procesu odkształcania w próżni i w atmosferze gazu obojętnego. Zmiany mikrostruktury badanych stopów, zachodzące w charakterystycznych stadiach obróbki cieplno-plastycznej, badano za pomocą transmisyjnego mikroskopu elektronowego (TEM). Ustalono, że wielkość naprężenia zmniejsza się wraz ze wzrostem temperatury i wielkości odkształcenia. Również energia aktywacji Q w dużym stopniu zależy zarówno od temperatury jak i prędkości odkształcania. Wyniki obserwacji mikrostruktury TEM wykazały, że dynamiczne mięknięcie materiałów jest głównie wynikiem zachodzących procesów zdrowienia dynamicznego i rekrystalizacji stopu aluminium 6xxx.

19

Charakterystyka odkształcalności i mikrostruktury nadstopu Ni-Fe po odkształcaniu plastycznym na gorąco

Ducki K. J.

Hutnik, Wiadomości Hutnicze

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2014

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Vol. 81, nr 8

534--540

PL

W pracy przedstawiono wyniki badań wpływu parametrów odkształcania plastycznego na gorąco na mikrostrukturę i właściwości plastyczne nadstopu typu IN-718. Badania odkształcalności stopu wykonano metodą skręcania na gorąco na plastomerze skrętnym. Próbki skręcano do zerwania w zakresie temperatury 900÷1150°C ze stałą prędkością odkształcania 0,1 i 1,0 s-1. Do analizy ilościowej zastosowano program MET-ILO i wyznaczono podstawowe parametry stereologiczne badanych mikrostruktur. Wykazano, że średnia wielkość ziarna po rekrystalizacji wzrasta w miarę podwyższania temperatury odkształcania i wzrostu prędkości odkształcania. Opracowano zależność funkcyjną pomiędzy średnią wielkością ziarna zrekrystalizowanego a parametrem Zenera-Holomona oraz oszacowano energię aktywacji odkształcania plastycznego na gorąco.

EN

The paper presents the results of research concerning the influence of hot deformation parameters on the microstructure and plastic properties of an IN-718 type superalloy. The hot deformation characteristics of alloy were investigated by hot torsion tests using of torsional plastometer. The tests were executed at constant strain rates of 0.1 and 0.1 s-1, and testing temperature in the range of 900 to 1150°C and were conducted until total fracture of the samples. A quantitative analysis of the investigated microstructures was carried out by means of program MET-ILO and the main stereological parameters were determined. It was found that mean grain size after recrystallization increases with an increasing deformation temperature and with growth of strain rate. Functional relation between the mean recrystallized grain size and the Zener-Hollomon parameter been developed and activation energy of the hot plastic deformation has been estimated.

20

A quantitative description of the microstructure of hot-deformed Ni-Fe superalloy

Ducki K. J., Mendala J., Swadźba L.

Inżynieria Materiałowa

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2013

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Vol. 34, nr 4

261--264

EN

The paper presents the results of research concerning the inﬂuence of hot deformation parameters on the microstructure and plastic properties of an Incolloy 718 type superalloy. The hot deformation characteristics of alloy were investigated by hot torsion tests using of Setaram torsional plastometer of type 7 MNG. The tests were executed at constant strain rates of 0.1 and 0.1 s-1, and testing temperature in the range of 900 to 1150°C and were conducted until total fracture of the samples. The structural inspections were perfonned on microsections taken from plastometric samples after so called “freezing”, i.e. rapid cooling of samples in water from deformation temperature. Plastic properties of the alloy were characterized by worked out ﬂow curves and the temperature relationships of ﬂow stresses and the strain limits. The ﬂow stress of the torsion tests showed a single peak in the flow stress-strain curves, and indicated that recovery and dynamic recrystallization took place during the hot deformation. A quantitative analysis ofthe investigated microstructures was carried out by means of a computer program MET-ILO and the main stereological parameters were determined. For the analyzed microstructures the relationships between the process parameters and the recrystallized grain size, inhomogenity and shape of grains have been determined. It was found that mean grain size after recrystallization increases with an increasing deformation temperature and with growth of strain rate. Functional relation between the Zener-Hollomon parameter and the mean grain size after dynamic recrystallization have been developed and activation energy of the hot plastic deformation process has been estimated.

PL

W pracy przedstawiono wyniki badań wpływu parametrów odkształcania plastycznego na gorąco na mikrostrukturę i właściwości plastyczne nadstopu typu Inconel 718. Badania odkształcalności stopu wykonano metodą skręcania na gorąco na plastomerze skrętnym typu 7 MNG ﬁrmy Setaram. Próbki cylindryczne pełne skręcano do zerwania w zakresie temperatury 900÷1150°C ze stałą prędkością odkształcania 0,1 i 1,0 s-1. Badania strukturalne prowadzono na odcinkach pobranych z próbek plastometrycznych po ich ,,zamrożeniu”, tj. oziębianiu w wodzie bezpośrednio z temperatury skręcania. Na wyznaczonych krzywych płynięcia określono wskaźniki charakteryzujące właściwości plastyczne stopu w próbie skręcania i odkształcalność graniczną. Opracowane krzywe płynięcia plastycznego stopu wykazują pojedyncze maksimum naprężenia uplastyczniającego, co świadczy o przebiegu procesu zdrowienia i rekrystalizacji dynamicznej podczas odkształcania na gorąco. Do analizy ilościowej zastosowano program komputerowy MET-ILO i wyznaczono podstawowe parametry stereologiczne badanych mikrostruktur. Dla analizowanych mikrostruktur wyznaczono zależności pomiędzy parametrami odkształcania plastycznego a wielkością, jednorodnością i kształtem ziarna zrekrystalizowanego. Wykazano, że średnia wielkość ziarna po rekrystalizacji wzrasta w miarę podwyższania temperatury odkształcania i wzrostu prędkości odkształcania. Opracowano zależność funkcyjną pomiędzy parametrem Zenera-Holomona a średnią wielkością ziama po rekrystalizacji dynamicznej oraz oszacowano energię aktywacji procesu odkształcania plastycznego na gorąco.