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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 Critical Conditions and Kinetics Required for Dynamic Recrystallization in a High-Carbon Tool Steel

Zhang Yong-Ji, Wu Guang-Lian, Wu Shang-Wen

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

119--125

EN

A hot compression test was conducted on a Gleeble-3500 thermo-simulation machine to study the critical conditions and kinetics of dynamic recrystallization in a high-carbon tool steel. The critical conditions for the initiation of dynamic recrystallization were determined using the working-hardening theory. The quantitative relationship between the critical characteristics of dynamic recrystallization and the hot deformation parameters were elucidated based on two different methods: the apparent method and physically based method. It was found that the two methods both have high applicability for the investigated steel, but the physically-based method needs less parameters and makes it possible to study the effect of different factors. A dynamic recrystallization kinetics model was used to calculate the recrystallization volume fraction under different conditions. The calculation results matched well with the data obtained from the flow 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

Experimental characterization of the AA7075 aluminum alloy using hot shear compression test

Bhujangrao Trunal, Veiga Fernando, Froustey Catherine, Guérard Sandra, Iriondo Edurne, Darnis Philippe, Mata Franck Girot

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

95--111

EN

The experimental characterization of the material under shear loading is essential for researchers to study the plastic behavior of materials during manufacturing processes. Indeed, regardless of the loading mode, ductile materials mainly deform plastically under shear loading. Thus, for such material behavior analysis, shear tests are very useful. In this paper, a test procedure is defined to characterize the shear deformation of AA7075 aluminum alloy at high strain under compression loading. The Finite Element (FE) simulation is used to select the suitable specimen geometry for the testing. Finally, the experimental tests are carried out using a conventional compression device at a constant strain rate of 0.1 s−1 and at an elevated temperature of 20–500 °C. The results show that the drop in the flow stress curved relative to the increase in temperature exhibits the softening mechanism. The homogeneous behavior of the shear strain along the shear region was also observed and shown by the macro and micro images. The effect of temperature and equivalent strain on the evolution of the microstructure is discussed in detail. It is discovered that, various dynamic recrystallization mechanisms were recorded for aluminum alloy AA7075 depending on the imposed strain conditions.

6

Dynamic failure mechanism of copper foil in laser dynamic flexible forming

Shen Zongbao, Zhang Lei, Li Pin, Liu Kai, Lin Youyu, Zhou Guoyang, Wang Yang, Zhang Jindian, Liu Huixia, Wang Xiao

Materials Science Poland

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2020

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Vol. 38, No. 4

684--692

EN

Laser dynamic flexible forming (LDFF) is a novel high velocity forming (HVF) technology, in which the foil metal is loaded by laser shock wave. Strain localization is readily to occur around the bulge edge, which will result in the ultimate dynamic failure. In this work, the microstructures before and after dynamic fracture are characterized by transmission electron microscopy (TEM) to investigate the dynamic failure mechanism. The plastic deformation regions of copper foil are composed of shock compression, strain localization and bulge. Microstructure refinement was observed in three different plastic deformation regions, particularly, dynamic recrystallization (DRX) occurs in the strain localization and bulge regions. In bulge region, extremely thin secondary twins in the twin/matrix (T/M) lamellae are formed. The microstructure features in the strain localization region show that superplastic flow of material exists until fracture, which may be due to DRX and subsequent grain boundary sliding (GBS) of the recrystallized grains. The grain coarsening in strain localization region may degrade the material flowing ability which results in the dynamic fracture.

7

Microstructure evolution and property analysis of commercial pure Al alloy processed by radial-shear rolling

Gamin Yu. V., Akopyan T. K., Koshmin A. N., Dolbachev A. P., Goncharuk A. V.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

674--683

EN

The features of microstructure formation and properties of commercial pure aluminum alloy (Al 99.5%) obtained by radial-shear rolling (RSR) method at the different heating temperatures of 25, 200, 250, 300 and 350 °C were examined. In this paper, the rods with diameter of 14 mm were obtained from initial billet with diameter of 60 mm in five passes. The microstructure analysis with electron backscatter diffraction (EBSD), measurements of microhardness HV over cross-section, and tension test for determination of mechanical properties were carried out for these rods. The FEM simulation of RSR process and calculation of Zener–Hollomon parameter (Z) were carried out with Software QFORM. The obtained rods have the gradient microstructure typical of RSR characterized by surface layer with ultrafine grain structure (UFG) and grain size from 0.3 to 5 µm. In the central part of rod, the fiber deformed structure with minimal fraction of recrystallized grains (< 5%) is formed. This combination is optimal for simultaneous achievement of high strength (UTS ~ 107–110 MPa; YS ~ 100–109 MPa; ~ 35–40 HV) and ductility (El ~ 15–30%). The most intensive growth of plastic properties is observed at rolling temperatures close to the temperature of the onset of recrystallization, it is associated with additional deformational heating of surface layers and the formation of partially recrystallized structure. The obtained distribution dependences of average size of dynamic recrystallized grain on Zener–Hollomon parameter showed that the decrease in parameter Z leads to the increase in size of recrystallized grain for RSR process.

8

Emami S., Sadeghi-Kanani S., Saeid T., Khan F.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

498--513

EN

Dissimilar joints of AISI 430 ferritic and AISI 304L austenitic stainless steels were produced by friction stir welding process. A sound and defect-free joint was obtained at 1 mm tool offset towards the ferritic sample located in the advancing side, and at rotational and welding speeds of 560 rpm and 50 mm/min, respectively. The XRD measurements revealed the presence of approximately equal volume fractions of ferrite (51%) and austenite (49%) phases in the stir zone (SZ). The formation of low-angle grain boundaries through the occurrence of dynamic recovery along with the presence of shear texture components in both constituent phases of ferrite and austenite in the SZ approved the occurrence of continuous dynamic recrystallization throughout the evolved microstructure. Moreover, microstructural observations showed the formation of necklace structure through the microstructure of ferrite in the SZ. Taylor map approved the strain localization in the ferrite phase. Micro-hardness measurement indicated that the hardness value is increased in the SZ. The result of tensile test showed that fracture occurred from less ductile ferritic base metal.

9

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.

10

Practical Approach to Determining Dynamic Recrystallization Parameters Using Finite Element Optimization of Backward Extrusion Process

Irani Missam, Joun Mansoo

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

1175--1182

EN

In this study, we present a new method for obtaining the parameters of the Johnson-Mehl-Avrami-Kolmogorov equation for dynamic recrystallization grain size. The method consists of finite-element analysis and optimization techniques. An optimization tool iteratively minimizes the error between experimental values and corresponding finite-element solutions. Isothermal backward extrusion of the AA6060 aluminum alloy was used to acquire the main parameters of the equation for predicting DRX grain size. We compared grain sizes predicted using optimized and reference parameters with experimental values from the literature and found better agreement when the optimized parameters were applied.

11

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.

12

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.

13

Numerical analysis of damage during hot forming

Szyndler Joanna, Muhammad Imran Muhammad, Muhammad Junaid Afzal Muhammad Junaid, Bambach Markus

Computer Methods in Materials Science

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2018

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Vol. 18, No. 3

107--114

EN

The main aim of the presented research is the analysis of damage evolution in 16MnCrS5 steel during hot forming based on results obtained from finite element modelling. Particular attention is put on the interaction between dynamic recrystallization (DRX) and damage initiation at the matrix-inclusion interface. Moreover, a modified Gurson-Tvergaard- Needleman (GTN) model is proposed with the nucleation criterion taken from an extended Horstemeyer model, which predicts damage nucleation based on material softening due to the DRX and stress state in the material.

14

Y Addition Effects on Hot Deformation Behavior of Cu-Zr Alloys with High Zr Content

Tian K., Tian B., Volinsky A. A., Zhang Y., Liu Y., Du Y.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

875--882

EN

Isothermal hot compression experiments were carried out using the Gleeble-1500D thermal mechanical simulator. The flow stress of the Cu-1%Zr and Cu-1%Zr-0.15%Y alloys was studied at hot deformation temperature of 550°C, 650°C, 750°C, 850°C, 900°C and the strain rate of 0.001 s-1, 0.01 s-1, 0.1 s-1, 1 s-1, 10 s-1. Hot deformation activation energy and constitutive equations for two kinds of alloys with and without yttrium addition were obtained by correlating the flow stress, strain rate and deformation temperature. The reasons for the change of hot deformation activation energy of the two alloys were analyzed. Dynamic recrystallization microstructure evolution for the two kinds of alloys during hot compression deformation was analyzed by optical and transmission electron microscopy. Cu-1%Zr and Cu-1%Zr-0.15%Y alloys exhibit similar behavior of hot compression deformation. Typical dynamic recovery occurs during the 550-750°C deformation temperature, while dynamic recrystallization (DRX) occurs during the 850-900°C deformation temperature. High Zr content and the addition of Y significantly improved Cu-1%Zr alloy hot deformation activation energy. Compared with hot deformation activation energy of pure copper, hot deformation activation energy of the Cu-1%Zr and Cu-1%Zr-0.15%Y alloys is increased by 54% and 81%, respectively. Compared with hot deformation activation energy of the Cu-1%Zr alloy, it increased by 18% with the addition of Y. The addition of yttrium refines grain, advances the dynamic recrystallization critical strain point and improves dynamic recrystallization.

15

Effect of Nitrogen on the Dynamic Recrystallization Behaviors of Vanadium and Titanium Microalloyed Steels

Baochun Z., Tan Z., Guiyan L., Qiang L.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

379--386

EN

The hot deformation behaviors of vanadium and titanium microalloyed steels containing different nitrogen contents were studied by performing hot compression tests at various temperatures ranging from 900 to 1050°C and strain rates ranging from 0.1 to 10 s-1. The flow stress curves of the experimental steels were analyzed and the effect of nitrogen on the hot deformation behaviors of the vanadium titanium and nitrogen microalloyed steels was discussed. The results reveal that the flow stress increases with increasing nitrogen addition and the critical strain for the onset of dynamic recrystallization(DRX) also increases by adding nitrogen. Therefore, larger strain should be applied to start DRX in the experimental steel containing higher nitrogen content. The material constants and activation energies for hot deformation were determined by regression method and the effect of nitrogen on the activation energy was also discussed referring to the activation energies from the previous researches. It is found that higher nitrogen content contributes to higher activation energy for hot deformation. Furthermore, the DRX kinetics models for the experimental steels were constructed by regression method and the effect of nitrogen on the DRX rate under various deformation conditions was analyzed. And the inhibition of DRX by increasing nitrogen content is confirmed.

16

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.

17

Finite Element Modelling of Titanium Aluminides

Sizova I., Sviridov A., Günther M., Bambach M.

Computer Methods in Materials Science

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2017

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Vol. 17, No. 1

51--58

EN

Hot forging is an important process for shaping and property control of lightweight titanium aluminide parts. Dynamic recrystallization and phase transformations play an essential role for the resulting grain size and accordingly the mechanical properties. Due to the fact that titanium aluminides require forging under isothermal conditions, reliable process modeling is needed to predict the microstructure evolution, to optimize the process time and to avoid excessive die loads. In the present study an isothermal forging process of a compressor blade made of TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B, at. %) is modeled using the Finite Element (FE) – Software Q-Form. A microstructure model describing the microstructure evolution during forging is presented. To calibrate the model, the high-temperature deformation behavior was investigated using isothermal compression tests. The tests were carried out at temperatures from 1150°C to 1300°C, applying strain rates ranging from 0.001s-1 to 0.5s-1, up to a true strain of 0.9. The experimentally determined flow stress data were described with model equations determined form the course of the strain hardening rate in Kocks-Mecking plots. An isothermal forging process of a compressor blade was carried out and used to validate the results from the FE simulations.

PL

Plastyczna przeróbka na gorąco jest ważnym procesem po-zwalającym nadawać kształt i kontrolować własności wyrobów z glinków tytanu. Dynamiczna rekrystalizacja i przemiany fazowe odgrywają kluczową rolę w kształtowaniu końcowej wielkości ziarna i, w konsekwencji, własności mechanicznych wyrobu. Ponieważ glinki tytanu wymagają kucia w warunkach izotermicznych, potrzebny jest dokładny model rozwoju mikrostruktury aby umożliwić optymalizację czasu trwania procesu i aby uniknąć przeciążenia matryc. W niniejszej pracy proces kucia łopatki kompresora został zamodelowany metodą elementów skończonych (MES) z wykorzystaniem programu Q-Form. Badanym materiałem był stop TNB-V4 (Ti—44.5Al-6.25Nb-0.8Mo-0.IB, at. %). W pracy przedstawiono zastosowany model rozwoju mikrostruktury. Model został skalibrowany na podstawie wyników prób ściskania na gorąco w warunkach izotermicznych. Badania przeprowadzono w temperaturach w zakresie 1150°C - 1300°C i dla prędkości odkształcenia w zakresie 0.001 s"1 d 0.5 s' . Całkowite odkształcenie w tych próbach wynosiło 0.9. Wyznaczone doświadczalnie naprężenie uplastyczniające zostało opisane za pomocą prędkości umocnienia zgodnie z krzywymi Kocksa-Meckinga. Fizyczny proces kucia łopatki kompresora został wykorzystany do walidacji modelu MES.

18

Analytical Descriptions of Dynamic Softening Mechanisms for Ti-13Nb-13Zr Biomedical Alloy in Single Phase and Two Phase Regions

Quan G.-Z., Wang X., Li Y.-L., Zhang L.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

2029--2043

EN

Dynamic softening behaviors of a promising biomedical Ti-13Nb-13Zr alloy under hot deformation conditions across dual phase α + β and single phase β regions were quantitatively characterized by establishing corresponding dynamic recovery (DRV) and dynamic recrystallization (DRX) kinetic models. A series of wide range hot compression tests on a Gleeble-3500 thermo-mechanical physical simulator were implemented under the strain rate range of 0.01-10 s−1 and the temperature range of 923-1173 K. The apparent differences of flow stress curves obtained in dual phase α + β and single phase β regions were analyzed in term of different dependence of flow stress to temperature and strain rate and different microstructural evolutions. Two typical softening mechanisms about DRV and DRX were identified through the variations of a series of stress-strain curves acquired from these compression tests. DRX is the dominant softening mechanism in dual phase α + β range, while DRV is the main softening mechanism in single phase β range. The DRV kinetic model for single phase β region and the DRX kinetic model for dual phase α + β region were established respectively. In addition, the microstructures of the compressed specimens were observed validating the softening mechanisms accordingly.

19

Perceptive comparison of mean and full field dynamic recrystallization models

Madej Ł., Sitko M., Pietrzyk M.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 4

569--589

EN

Review of dynamic recrystallization models is the subject of the present work. Development of both mean field and full field approaches during last three decades is presented and discussed. Conventional mean field models based on closed form equations as well as differential equations are presented first. Then full field models are elaborated focusing on the cellular automata approach as an example. Capabilities as well as limitations and drawbacks of these approaches are highlighted based on the set of case studies. Experimental data for validation of models were obtained from uniaxial compression tests at Gleeble 3800 thermo-mechanical simulator.

20

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.