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Prediction of High Strain Rate Flow Behavior of 7175 Aluminum Alloy Based on Arrhenius-Type Constitutive Equations

Shin Young-Chul, Joung Dae-Kwan, Ha Seong-Ho, Choi Ho-Joon, Hyun Soong-Keun

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1361--1364

EN

The flow behavior of 7175 aluminum alloy was modeled with Arrhenius-type constitutive equations using flow stress curves during a hot compression test. Compression tests were conducted at three different temperatures (250°C, 350°C, and 450°C) and four different strain rates (0.005, 0.05, 0.5, and 5 s-1). A good consistency between measured and set values in the experimental parameters was shown at strain rates of 0.005, 0.05, and 0.5 s-1, while the measured data at 5 s-1 showed the temperature rise of the specimen, which was attributable to deformation heat generated by the high strain rate, and a fluctuation in the measured strain rates. To minimize errors in the fundamental data and to overcome the limitations of compression tests at high strain rates, constitutive equations were derived using flow curves at 0.005, 0.05, and 0.5 s-1 only. The results indicated that the flow stresses predicted according to the derived constitutive equations were in good agreement with the experimental results not only at strain rates of 0.005, 0.05, and 0.5 s-1 but also at 5 s-1. The prediction of the flow behavior at 5 s-1 was correctly carried out by inputting the constant strain rate and temperature into the constitutive equation.

2

Effects of V-Ti on Dynamic Recrystallization Behavior and Hot Deformation Activation Energy of 30MSV6 Micro-alloyed Steel

Tavaei K., Meysami A.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

1195--1200

EN

In the current study, the hot deformation of medium carbon V-Ti micro-alloyed steel was surveyed in the temperature range of 950 to 1150°C and strain rate range of 0.001 to 1 s-1 after preheating up to 1200°C with a compression test. In all cases of hot deformation, dynamic recrystallization took place. The influence of strain rate and deformation temperature on flow stress was analyzed. An increase in the strain rate and decrease in the deformation temperature postponed the dynamic recrystallization and increased the flow stress. The material constants of micro-alloyed steel were calculated based on the constitutive equations and Zener-Hollomon parameters. The activation energy of hot deformation was determined to be 458.75 kJ/mol, which is higher than austenite lattice self-diffusion activation energy. To study the influence of precipitation on dynamic recrystallization, the stress relaxation test was carried out in a temperature range of 950 to 1150°C after preheating up to 1200°C. The results showed no a stress drop while representing the interaction of particles with dynamic recrystallization.

3

Experimental investigation and modelling of hot forming B₄C/AA6061 low volume fraction reinforcement composites

Zheng K., Lin J., Wu G., Hall R. W., Dean T. A.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 2

457--469

EN

This paper presents an experimental investigation of the hot deformation behaviour of 15% B₄C particle reinforced AA6061 matrix composites and the establishment of a novel corresponding unified and physically-based visco-plastic material model. The feasibility of hot forming of a metal matrix composite (MMC) with a low volume fraction reinforcement has been assessed by performing hot compression tests at different temperatures and strain rates. Examination of the obtained stress-strain relationships revealed the correlation between temperature and strain hardening extent. Forming at elevated temperatures enables obvious strain rate hardening and reasonably high ductility of the MMC. The developed unified material model includes evolution of dislocations resulting from plastic deformation, recovery and punching effect due to differential thermal expansion between matrix and reinforcement particles during non-steady state heating and plastic straining. Good agreement has been obtained between experimental and computed results. The proposed material model contributes greatly to a more thorough understanding of flow stress behaviour and microstructural evolution during the hot forming of MMCs.

4

Plastyczność i mikrostruktura odkształcanego na gorąco stopu magnezu AZ61

Kuc D., Tkocz M., Bednarczyk I., Hadasik E., Śliwa R.

Rudy i Metale Nieżelazne

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2012

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R. 57, nr 5

298-304

PL

W artykule zaprezentowano wyniki badań dotyczących wpływu parametrów odkształcenia na zmianę naprężenia uplastyczniającego oraz mikrostrukturę stopu magnezu AZ61 (oznaczenie wg norm ASTM). Próby jednoosiowego ściskania na gorąco przeprowadzono w zakresie temperatury od 250 do 400 [stopni] C i prędkości odkształcenia od 0,01 do 1 s-1. Analiza wyników badań plastometrycznych oraz obserwacja mikrostruktury w pozwoliły ustalić, który mechanizm odkształcenia plastycznego - poślizg czy bliźniakowanie - dominuje w określonych warunkach kształtowania stopu AZ61. Otrzymane wyniki porównano z rezultatami prowadzonymi wcześniej dla stopu typu AZ31 o mniejszej zawartości aluminium.

EN

The current trends in the automotive and aircraft focus first and foremost on a reduction of the vehicle weight and saving energy, thereby protecting the environment. Such a set of technical, economical and ecological aspects arouses a considerable interest of the industry in light alloys. Owing to a number of their advantageous mechanical properties including, first of all, low density (1.74 g/cm3), magnesium alloys are more and more frequently used as an engineering material. There is a regular increase visible in the number of components made of magnesium alloys in the car structure. However, for the production of components from magnesium alloys, casting processes are still most often applied. Alloys used for plastic working are less popular compared to those processed via casting and therefore, the number of their grades is much smaller. The number of alloying components in cast magnesium alloys is always higher than in alloys subject to plastic working. Alloys from the group Mg?Al?Zn?Mn have the best set of properties, for they contain as much as 8 % Al with an addition of Mn (up to 2 %) and Zn (up to 1.5 %). From among elements subjected to plastic working, sheet metal deserves special attention, for it can be applied for the construction of light vehicles. In connection with the complexity of the phenomena which take place in the microstructure, a number of studies in the field of Mg-Al-Zn alloys subjected to plastic working are focused on detecting the mechanisms of deformation and structure reconstruction during deformation. There are two main mechanisms of deformation of magnesium alloy - slip and twinning. Magnesium alloys crystallize with hexagonal close pack (HCP) structure and they have very limited number of slip systems. The paper presents the research results on the effect of deformation parameters on flow stress and microstructure of AZ61 magnesium alloy. Hot compression tests were conducted at the temperature range of 250 to 400 [degrees] C and at the strain rate range of 0.01 to 10 s-1. Analysis of the plastometric tests results as well as examination of microstructure at different deformation phases allowed to determine what kind of deformation mechanism - slip or twinning - dominates in the specific conditions of AZ61 alloy forming. The results were compared to the ones obtained for AZ31 magnesium alloy.

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Mechanical properties of high speed steel used in hot strip work rolls

Ziadi A., Meciridi M.A., Bouafia F., Belhenini S.

Advances in Materials Science

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2007

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Vol. 7, nr 2(12)

319-326

EN

The rolls in the finishing stands must have good resistance to both wear and fire cracks: The use of high-speed steel at the finishing stands has shown satisfactory results. The composition of this high-alloyed steel is an important parameter as the most significant change lays on the type, morphology, and volume fraction of the eutectics carbides. The heat treatment of these products consists of high temperature austenization followed by quenching and two temperings, as required in order to increase their overall hardness and to completely eliminate residual austenite. The influence of tempering temperatures on the mechanical properties of these products, determined using tensile, hot compression and fracture toughness tests, was studied in this research work. Their corresponding failure micromechanisms were defined by means of the analysis of fracture surfaces.

6

Plasticity of Ti-48Al-2Cr-2Nb alloy

Szkliniarz W., Hadasik E., Kościelna A., Kawalla R.

Archives of Civil and Mechanical Engineering

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2004

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Vol. 4, no 3

57-65

EN

The paper presents the results of experiments carried out in order to evaluate the plastic workability of Ti-48AI-2Cr-2Nb alloy subjected to hot compression tests. A significant influence of deformation temperature and, first of all, of the heating conditions on the results obtained has been shown. It has been found that deformation conducted under appropriate conditions and coupled with recrystallization annealing allows us to obtain a fine-grained "duplex" type microstructure. This, however, requires further research in order to define the role of the deformation parameters, initial microstructure and heating conditions in plastic forming of this group of alloys.

PL

Stopy na osnowie faz międzymetalicznych z układu Ti-AI należą do materiałów szczególnie trudnych z punktu widzenia technologii ich wytwarzania i przetwarzania. Problemy technologiczne stwarza zwłaszcza przeróbka plastyczna tych stopów, które oznaczają się małą podatność technologiczną objawiającą się w postaci ograniczonej odkształcalności i dużych oporów kształtowania plastycznego. Oparta na próbie ściskania na gorąco ocena podatności na kształtowanie plastyczne stopu Ti-48AI-2Cr-2Nb wykazała, że charakteryzuje się on dużym wartościami maksymalnego nacisku jednostkowego. Ze wzrostem temperatury odkształcenia wielkość ta wyraźnie maleje z 1070 MPa w temperaturze 1173 K do 630 MPa w temperaturze 1373 K. Krzywe pokazujące zależność średniego nacisku jednostkowego od odkształcenia rzeczywistego charakteryzują się łagodnie zarysowanym maksimum odpowiadającym odkształceniu ok. 0.2 i niewielkim spadkiem nacisku w miarę zwiększenia odkształcenia. Próbki ściskane bezpośrednio po krótkotrwałym wygrzewaniu w temperaturze próby wykazywały wady w postaci wyraźnych rys lub pęknięć na powierzchni bocznej. Jednogodzinne wygrzewanie w temperaturze próby bezpośrednio przed próbą ściskania bez zmniejszania wartości maksymalnego nacisku jednostkowego spowodowało usunięcie tych niekorzystnych efektów. Przyczyn tego stanu rzeczy należy upatrywać w zwiększeniu równomierności rozkładu temperatury na przekroju z powodu złego przewodnictwa cieplnego stopów na osnowie faz międzymetalicznych. W wyniku odkształcenia w badanym zakresie temperatury występuje tendencja do odkształcenia płytkowej mikrostruktury i ukierunkowania jej zgodnie z kierunkiem odkształcenia oraz fragmentacji i sferoidyzacji płytek. W mikrostrukturze próbki odkształcanej w 1373 K widoczne są efekty świadczące o przebiegu procesu rekrystalizacji. Zastosowanie wyżarzania rekrystalizującego. prowadzonego w standardowych dla tego stopu warunkach. spowodowało wystąpienie wyraźnych efektów rekrystalizacji i rozdrobnienie ziarna badanego stopu. Największe rozdrobnienie uzyskano dla stopu odkształcanego w temperaturze 1323 K. Efektem rekrystalizacji jest otrzymanie mikrostruktury typu "duplex" z ziarnami o morfologii płytkowej i równoosiowej.