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1

Effect of Cyclic Heat Treatment on Microstructure Evolution of TA15 Titanium Alloy

Zhang Dan-Ya, Nong Zhi-Sheng, Wang Tian-Xing

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

869--874

EN

To investigate the effect of cyclic heat treatment on the microstructure evolution of titanium alloys, TA15 alloys were subjected to different numbers of heat treatment cycles at various temperatures in the (α + β) two-phase region. The resulting microstructure and hardness of the alloy were characterized by using the metallographic microscopy, scanning electron microscopy, and Vickers hardness testing. The morphology of the initial TA15 alloy was nearly equiaxed structure. The α phase content, thickness of the oxygen-rich α layer, and hardness of the TA15 alloy increased with the number of cycles. The morphology of the TA15 alloy changed into the Widmannstatten structure when the alloy underwent six cycles of heat treatment between 970 and 800°C. The thickness of the oxygen-rich α layer and hardness of the alloy increased with the lower limit temperature of the cyclic heat treatment. Compared with the number of cycles, the lower limit temperature of the cyclic heat treatment was a more significant factor on the microstructure evolution of the TA15 titanium alloy.

2

Microstructure, mechanical properties and corrosion behavior of friction stir processed AA2014 alloy

Satyanarayana M. V. N. V., Kumar Adepu, Jain Vikram Kumar S., Kumar Rahul, Mishra Sushil

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e43, 2023

EN

In the present study, a large-area stir zone (SZ) was fabricated in AA2014 alloy using multi-pass friction stir processing (FSP) with pin overlapping. The microstructure evolution, crystallographic texture, precipitation phenomenon, and tensile behavior were studied and reported. The microstructure of the large-area SZ consists of equiaxed fine grains with a high density of high angle boundaries caused by dynamic recovery (DRV) and continuous-dynamic recrystallization (C-DRX), and the grain refining has been uniform in each overlapping pass (the grain size within 4-7 μm range). The material flow around the pin caused by the stirring action of the tool contributed to the creation of a strong Brass-{110}<112>and A-{110}<111>components in the first pass of SZ. Unlike first pass SZ, the second to fifth-pass SZ presents Copper-{112}<111>and Cube- {001}<100>components due to an increase of heat input by the shoulder to participate multiple times on each overlapping SZ. The hardness and strength of the FSP sample were found to be lowered relative to a base metal. Simultaneously, the SZ ductility increased after FSP by 155% due to the material softening and dissolution of Al2Cu precipitates in the SZ. Kocks-Mecking plots of the BM and FSP samples witnessed the Stage-III of work-hardening behavior. The fine-grain structure and precipitation phenomenon in the FSP sample resulted in better corrosion resistance than the base metal.

3

Microstructure evolution of pure titanium during hydrostatic extrusion

Wojtas Daniel, Maj Łukasz, Wierzbanowski Krzysztof, Jarzębska Anna, Chulist Robert, Kawałko Jakub, Trembecka-Wójciga Klaudia, Bieda-Niemiec Magdalena, Sztwiertnia Krzysztof

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e9, 2023

EN

Regarding severely deformed materials of potentially high applicability in various industry branches, their microstructure evolution during processing is of vast significance as it enables to control or adjust the most essential properties, including mechanical strength or corrosion resistance. Within the present study, the microstructure development of commercially pure titanium (grade 2) in the multi-stage process of hydrostatic extrusion has been studied with the use of the well-established techniques, involving electron backscatter diffraction as well as transmission electron microscopy. Microstructural deformation-induced defects, including grain boundaries, dislocations, and twins, have been meticulously analyzed. In addition, a special emphasis has been placed on grain size, grain boundary character as well as misorientation gradients inside deformed grains. The main aim was to highlight the microstructural alterations triggered by hydroextrusion and single out their possible sources. The crystallographic texture was also studied. It has been concluded that hydrostatically extruded titanium is an exceptionally inhomogeneous material in terms of its microstructure as evidenced by discrepancies in grain size and shape, a great deal of dislocation-type features observed at every single stage of processing and the magnitude of deformation energy stored. Twinning, accompanied by grain subdivision phenomenon, was governing the microstructural development at low strains; whereas, the process of continuous dynamic recrystallization came to the fore at higher strains. Selected mechanical properties resulting from the studied material microstructure are also presented and discussed.

4

Thermal-mechanical finite element simulation of flat bar rolling coupled with a stochastic model of microstructure evolution

Szeliga Danuta, Czyżewska Natalia, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Piwowarczyk Michał, Poloczek Łukasz, Przybyłowicz Paweł, Rauch Łukasz, Wolańska Natalia

Computer Methods in Materials Science

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2022

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Vol. 22, No. 3

137--148

EN

It is generally recognized that the kinetics of phase transformations during the cooling of steel products depends to a large extent on the state of the austenite after rolling. Austenite deformation (when recrystallization is not complete) and grain size have a strong influence on the nucleation and growth of low-temperature phases. Thus, the general objective of the present work was the formulation of a numerical model which simulates thermal, mechanical and microstructural phenomena during multipass hot rolling of flat bars. The simulation of flat bar rolling accounting for the evolution of a heterogeneous microstructure was the objective of the work. A conventional finite-element program was used to calculate the distribution of strains, stresses, and temperatures in the flat bar during rolling and during interpass times. The FE program was coupled with the stochastic model describing austenite microstructure evolution. In this model, the random character of the recrystallization was accounted for. Simulations supplied information about the distributions of the dislocation density and the grain size at various locations through the thickness of the bars.

5

Microstructure Evolution and Wear Resistance of Boron-Bearing High Speed Steel Roll

Cheng Xiaole, Hou Jianqiang, Fu Hanguang

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

113--119

EN

The microstructure evolution of boron-bearing high speed steel roll materials after casting and tempering was investigated. The results indicate that as-cast boron-bearing high speed steel consists of martensitic matrix, retained austenite and different borocarbides. The as-cast alloy has a hardness above 64 HRC, and the borocarbides distribute along the grain boundaries. After RE-Mg-Ti compound modification treatment, obvious necking and broken network appear in the grain boundaries. The hardness of boron-bearing high speed steel roll materials reduces gradually with the increase of tempering temperature. Under the same conditions, the toughness of the modified roll material is higher than that of the unmodified roll material. Wear tests show that the wear resistance of boron-bearing high-speed steel modified by RE-Mg-Ti compound modification treatment is better.

6

Inter-relationship between microstructure evolution and mechanical properties in inertia friction welded 8630 low-alloy steel

Banerjee Amborish, Ntovas Michail, Da Silva Laurie, Rahimi Salaheddin, Wynne Bradley

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

244--262

EN

The evolution of microstructure and mechanical properties in AISI 8630 low-alloy steel subjected to inertia friction welding (IFW) have been investigated. The effects of three critical process parameters, viz. rotational speed, friction and forge forces, during welding of tubular specimens were explored. The mechanical properties of these weld joints, including tensile and Charpy V-notch impact were studied for determining the optimum welding parameters. The weld joints exhibited higher yield strength, lower hardening capacity and ultimate tensile strength compared to base metal (BM). The maximum strength and ductility combination was achieved for the welds produced under a nominal weld speed of ~ 2900–3100 rpm, the highest friction force of ~ 680–720 kN, and the lowest axial forging load of ~ 560–600 kN. The measured hardness distribution depicted higher values for the weld zone (WZ) compared to the thermo-mechanically affected zone (TMAZ), heat-affected zone (HAZ) and BM, irrespective of the applied welding parameters. The substantial increase in the hardness of the WZ is due to the formation of microstructures that were dominated by martensite. The observed microstructural features, i.e. the fractions of martensite, bainite and ferrite, show that the temperature in the WZ and TMAZ was above Ac3, whereas that of the HAZ was below Ac1 during the IFW. The fracture surface of the tensile and impact-tested specimens exhibited the presence of dimples nucleating from the voids, thus indicating a ductile failure. EBSD maps of the WZ revealed the formation of subgrains inside the prior austenite grains, indicating the occurrence of continuous dynamic recrystallisation during the weld. Analysis of crystallographic texture indicated that the austenite microstructure (i.e. FCC) in both the WZ and TMAZ undergoes simple shear deformation during IFW.

7

The Influence of the Microstructural Evolution on the Corrosion Resistance of Cold Drawn Copper Single Crystals in NaCl

Koralnik M., Dobkowska A., Adamczyk-Cieslak B., Mizera J.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

55--64

EN

The aim of the present work was to determine the influence of the microstructural evolution of copper single crystals with the initial orientations of <001> and <111> after cold drawing on their corrosion resistance. Transmission electron microscopy, X-ray diffraction, and electron backscattering diffraction were used to characterize the microstructural changes. To evaluate the corrosion resistance after deformation, open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization analyses were conducted. The microstructural observations showed the presence of dislocation cell structures and shear bands indeformed sample with initial orientation <001> single crystal, as well as a strongly-developed substructure in sample <111>. The material with initial orientation of <001> was more resistive in analyzed medium than material with the initial orientation of <111>.

8

Preparation and Microstructure Evolution of Continuous Unidirectional Solidification Tin Bronze Alloy at Different Continuous Casting Speed

Luo Jihui

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 2

118--122

EN

The mold temperature of the downward continuous unidirectional solidification (CUS) cannot be controlled higher than the liquidus of alloys to be cast. Therefore, the continuous casting speed becomes the main parameter for controlling the growth of columnar crystal structure of the alloy. In this paper, the tin bronze alloy was prepared by the downward CUS process. The microstructure evolution of the CUS tin bronze alloy at different continuous casting speeds was analysed. In order to further explain the columnar crystal evolution, a relation between the growth rate of columnar crystal and the continuous casting speed during the CUS process was built. The results show that the CUS tin bronze alloy mainly consists of columnar crystals and equiaxed crystals when the casting speed is low. As the continuous casting speed increases, the equiaxed crystals begin to disappear. The diameter of the columnar crystal increases with the continuous casting speed increasing and the number of columnar crystal decreases. The growth rate of columnar crystal increases with increasing of the continuous casting speed during CUS tin bronze alloy process.

9

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.

10

Investigation of the microstructure evolution and mechanical properties of a TC6 alloy blade preform produced by cross wedge rolling

Li Junling, Wang Baoyu, Fang Shuang, Chen Ping

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

91--101

EN

Cross wedge rolling (CWR) is one of the most effective plastic deformation methods utilized for the production of shaft parts or non-shaft preforms with refined grains and improved mechanical properties. The main goal of this work was to study the influence of CWR process parameters on the microstructure evolution and mechanical properties of a TC6 alloy and determine the suitable process parameters for a TC6 alloy blade preform fabricated with CWR. The results showed that the volume fraction of the equiaxed α phase (fα_e) decreased from ~ 0.38 to ~ 0.04 by increasing the initial deformation temperature, and the elongation (El) also decreased from ~ 19.6 to ~ 11.8% because dislocation slip first started in the equiaxed grains and then dispersed into the adjacent grains. Thus, additional equiaxed grains contributed to an increased plasticity. Moreover, with an increasing area reduction, the value of fα_e increased from ~ 0.14 to ~ 0.31, and the grain refinement and microstructure uniformity also increased. In addition, the El was significantly reduced by over 50%, but the ultimate tensile strength (UTS) and yield strength (YS) increased under WC (water cooling) conditions due to the precipitation of the acicular secondary α phase and pinning effect of the small equiaxed α phase. Based on the determined suitable parameters, the TC6 alloy blade preform was successfully manufactured by CWR, the microstructure was evenly distributed, and the UTS, YS and El were 1120.1 MPa, 1020.9 MPa and 15.2%, respectively, which meet the current technical requirements.

11

Effect of forging sequence on evolution of parameters controlling microstructure in multistage drop forging process

Skubisz Piotr, Lisiecki Łukasz, Majta Janusz, Krzysztof Muszka

Computer Methods in Materials Science

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2019

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Vol. 19, No. 3

81--88

EN

The study presents the comparative analysis of competitive techniques of forging and its effect on microstructure. Numerical modeling of temperature and strain fields let theoretical prediction of the microstructure development in multi-stage drop forging process consisting of progressive sequence of multiple blows in preforming and die-impression forging operations. The aim of the modeling was prediction of the parameters of austenite in as-forged condition, prior to direct cooling and microstructure parameters of transformation products. Dynamic recrystallization kinetics were analyzed with use of Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, taking advantage of numerically calculated of temperature, strain and strain-rate in selected location in the volume of the part. The obtained results show the possibility of look-ahead microstructure prediction in multi-stage hammer-forging process and form the basis for comprehensive selection of the forging process parameters aimed at producing required microstructure and its uniformity in the bulk.

PL

W pracy przedstawiono analizę porównawczą trzech sposobów kucia wielowykrojowego, która obejmuje dwa aspekty: 1) wpływ technologii na wskaźniki techniczno-ekonomiczne i siłowo-energetyczne oraz 2) rozkład w objętości i zmiany w czasie parametrów termo-mechanicznych, wpływających na kinetykę zjawisk dynamicznych w odkształcanym materiale oraz jakość odkuwki. Na podstawie wyników modelowania numerycznego oceniono wpływ zmian w technologii kucia na rozkład odkształceń, prędkość odkształcenia oraz temperatury w reprezentatywnych przekrojach odkuwki. Na ich podstawie wykonano modelowanie rozwoju mikrostruktury, oparte o klasyczne modele zarodkowania i rozrostu ziarna podczas rekrystalizacji dynamicznej i przemiany dyfuzyjnej przechłodzonego austenitu w oparciu o model JMAK. Jak wskazują wyniki modelowania, zmiany sposobu lub warunków kucia matrycowego stwarzają możliwości istotnego oddziaływania na rozkład odkształceń i silnie wpływają na temperaturę w objętości okuwki. To z kolei, może być wykorzystane do zniwelowania niekorzystnego wpływu warunków odkształcania na mikrostrukturę lub jej poprawy. Przedstawione wykresy pokazują istotne zmiany wielkości ziarna wraz z progresją odkształcenia w analizowanych punktach odkuwki. Jak widać, kształt odkuwki nie sprzyja uzyskaniu jednorodnego odkształcenia. Relatywnie małe odkształcenie podczas wstępnego spłaszczania pręta poprzedzający kilkunastosekundowy okres działania wysokiej temperatury, do momentu matrycowania, sprawia, że w obszarze zgrubienia prognozowane jest największe ziarno. Największe odkształcenie występuje w obszarze trzonu, jednakże sposób wstępnego kształtowania przedkuwki tego fragmentu odkuwki skutkuje przesunięciem w czasie odkształceń cząstkowych, przez co nawet na długości trzonu mogą wystąpić zmiany mikrostruktury. Zróżnicowanemu odkształceniu w zgrubieniu oraz trzonie odkuwki towarzyszą duże różnice prędkości odkształcenia, co przekłada się na kumulację odkształcenia w czasie. Analiza rozwoju mikrostruktury pozwala na odpowiednią korektę warunków kontrolowanego chłodzenia dla charakterystycznych fragmentów odkuwki, jak również odpowiednią korektę sekwencji i warunków realizacji kolejnych operacji kucia.

12

Microstructure characterization of 7055-T6, 6061-T6511 and 7A52-T6 Al alloys subjected to ballistic impact against heavy tungsten alloy projectile

Khan M. A., Wang Y., Malik A., Nazeer F., Yasin G., Khan W. Q., Ahmad T., Zhang H.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1484--1496

EN

A spray formed 7055 Al alloy, and traditional formed 6061 Al and 7A52 Al alloy were subjected to extrusion. Later 7055Al and 7A52 treated with T6 and 6061 Al treated with T6511 heat treatment. To investigate the microstructure evolution by optical microscopy (OM), scanning electron microscopy (SEM), electron back scattering diffraction (EBSD) and X-rays diffraction pattern (XRD) analysis were employed to observe the variation in mechanical properties and damages patterns of single layered aluminum alloys impacted by heavy tungsten alloy (WHA) projectile. During impact a substantial increase in temperature inside the target material caused melting on crater wall. The hard metastable intermetallic compound and pores were produced on penetration path owing to diffusion of projectile particles and rapid melt re-solidification. These compounds enhance the hardness (600-650 HV0.1/10) in the middle deformed channels of 7055 Al alloy target. In addition, small size pores, whirl-pool and white adiabatic shear bands were observed in 7A52 and 6061 Al alloys, respectively. The variation in hardness and microstructure of Al alloys target was limited within the 2 mm area from the perforation path. 7055-T6 Al alloy has demonstrated better ballistic protection in terms of strength, mass efficiency (N), depth of penetration (DOP) and penetration path diameter in comparison of other Al alloys.

13

Simulation of microstructure evolution during forging and heat treatment of Ti-6Al-3.5Mo-1.5Zr-0.3Si Titanium Alloy

Alimov Artem, Stebunov Sergey, Biba Nikolai

Computer Methods in Materials Science

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2018

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Vol. 18, No. 3

90--97

EN

The model of dynamic recrystallization of Ti-6Al-3.5Mo-1.5Zr-0.3Si has been developed based on experimental data and implemented in FEM code QForm. Kinetics of dynamic recrystallization was simulated by Johnson-Mehl-Avrami- Kolmogorov equation. Effect of aging time (1-6 h) and temperature (450-650 °C) on mechanical properties has been experimentally studied. The model of heat treatment of Ti-6Al-3.5Mo-1.5Zr-0.3Si has been developed and implemented in FEM code QForm. The model is capable to predict phase composition and hardness during and after arbitrary heat treatment within studied range. It was found that the highest hardness of Ti-6Al-3.5Mo-1.5Zr-0.3Si can be obtained by aging during 4-6 hours at 550°C after solution treatment at 960°C.

14

Materials modelling in industrial bulk metal forming processes and process chains

Hirt G., Bambach M., Lohmar J., Guvenc O., Henke T., Schwich G.

Computer Methods in Materials Science

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2015

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Vol. 15, No.1

5--12

EN

Bulk metal forming processes range from processes with a single deformation step such as certain closed-die forging operations to processes with many subsequent stages such as hot rolling, ring rolling or open die forging. Modelling of these manufacturing processes requires both precise process models as well as adequate material models. Microstructure evolution by recrystallization is decisive in all of these processes since the microstructure determines the flow stress and hence the forming forces but it also influences the product properties. In this context, the propagation of variations in the processing conditions and in the material behavior are of special importance and methods for the quantification of uncertainties and their effect on model predictions are required. Such questions can be approached using models of different complexity on various scales as shown in the following examples: In closed die forging of a gear wheel from 25MoCr4 alloy the complex geometry requires a Finite Element process model which in this case is combined with a JMAK type material model. In plate rolling a simplified process model can be applied successfully. Based on the slab theory, which is enhanced for spatial resolution of shear strain using a meta model derived by FEM, this model can simulate even longer roll pass schedules within seconds and offers the possibility to combine it with numerical optimization techniques. Recrystallization of a high-manganese steel in interpass times between hot rolling passes is an example where models with spatial resolution (CP-FEM and phase field) are combined on the micro-scale to predict the recrystallization kinetics based on physically meaningful variables such as grain boundary mobility. In ring rolling the process model must include the closed-loop control system of the rolling machine to achieve a realistic prediction of the process kinematics. Feedback control loops for up to eight kinematic degrees of freedom (velocities and positions of all radial, axial and guiding rolls) have been defined using virtual sensors integrated in the simulation. Offline coupling with microstructure simulation is used to predict the final grain size and determine under which conditions static recrystallization occurs during the rolling sequence.

15

Analysis Of Deformation And Microstructural Evolution In The Hot Forging Of The Ti-6Al-4V Alloy

Kukuryk M.

Archives of Metallurgy and Materials

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2015

|

Vol. 60, iss. 2A

597--604

EN

The paper presents the analysis of the three-dimensional strain state for the cogging process of the Ti-6Al-4V alloy using the finite element method, assuming the rigid-plastic model of the deformed body. It reports the results of simulation studies on the metal flow pattern and thermal phenomena occurring in the hot cogging process conducted on three tool types. The computation results enable the determination of the distribution of effective strain, effective stress, mean stress and temperature within the volume of the blank. This solution has been complemented by adding the model of microstructure evolution during the cogging process. The numerical analysis was made using the DEFORM-3D consisting of a mechanical, a thermal and a microstructural parts. The comparison of the theoretical study and experimental test results indicates a potential for the developed model to be employed for predicting deformations and microstructure parameters.

PL

W pracy przedstawiono analizę przestrzennego stanu odkształcenia dla procesu kucia wydłużającego stopu tytanu Ti-6Al-4V z wykorzystaniem metody elementów skończonych z założeniem sztywnoplastycznego modelu odkształcanego ciała. Przedstawiono wyniki prac związanych z symulacją schematu płynięcia metalu i zjawisk cieplnych w procesie kucia na gorąco w trzech rodzajach narzędzi kuźniczych. Rezultaty obliczeń umożliwiają określenie rozkładu intensywności odkształcenia, intensywności naprężeń, naprężeń średnich i temperatury w objętości odkuwki. Rozwiązanie uzupełniono o model rozwoju mikrostruktury podczas kucia. Analizę numeryczną wykonano z wykorzystaniem programu DEFORM-3D, składającego się z części mechanicznej, termicznej i mikrostrukturalnej. Porównanie teoretycznych i eksperymentalnych rezultatów badań wskazuje na możliwość zastosowania opracowanego modelu do prognozowania odkształceń i parametrów mikrostruktury.

16

Analysis of Deformation and Microstructural Evolution in the Hot Forging of the Ti-6Al-4V Alloy

Kukuryk M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 3A

1639--1647

EN

The paper presents the analysis of the three-dimensional strain state for the cogging process of the Ti-6Al-4V alloy using the finite element method, assuming the rigid-plastic model of the deformed body. It reports the results of simulation studies on the metal flow pattern and thermal phenomena occurring in the hot cogging process conducted on three tool types. The computation results enable the determination of the distribution of effective strain, effective stress, mean stress and temperature within the volume of the blank. This solution has been complemented by adding the model of microstructure evolution during the cogging process. The numerical analysis was made using the DEFORM-3D consisting of a mechanical, a thermal and a microstructural parts. The comparison of the theoretical study and experimental test results indicates a potential for the developed model to be employed for predicting deformations and microstructure parameters.

PL

W pracy przedstawiono analizę przestrzennego stanu odkształcenia dla procesu kucia wydłużającego stopu tytanu Ti-6Al-4V z wykorzystaniem metody elementów skończonych z założeniem sztywnoplastycznego modelu odkształcanego ciała. Przedstawiono wyniki prac związanych z symulacją schematu płynięcia metalu i zjawisk cieplnych w procesie kucia na gorąco w trzech rodzajach narzędzi kuźniczych. Rezultaty obliczeń umożliwiają określenie rozkładu intensywności odkształcenia, intensywności naprężeń, naprężeń średnich i temperatury w objętości odkuwki. Rozwiązanie uzupełniono o model rozwoju mikrostruktury podczas kucia. Analizę numeryczną wykonano z wykorzystaniem programu DEFORM-3D, składającego się z części mechanicznej, termicznej i mikrostrukturalnej. Porównanie teoretycznych i eksperymentalnych rezultatów badań wskazuje na możliwość zastosowania opracowanego modelu do prognozowania odkształceń i parametrów mikrostruktury.

17

Wpływ parametrów technologicznych na efektywność procesu kucia wydłużającego

Kukuryk M.

Hutnik, Wiadomości Hutnicze

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2014

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Vol. 81, nr 9

646--651

PL

W pracy przedstawiono wpływ parametrów procesu kucia wydłużającego na rozkład intensywności odkształcenia, naprężeń średnich i temperatury w objętości odkształcanego materiału. Do symulacji zjawisk płynięcia metalu i wymiany ciepła w procesie kucia wydłużającego stali narzędziowej w kowadłach skośnych wykorzystano metodę elementów skończonych. Rozwiązanie uzupełniono o model rozwoju mikrostruktury materiału podczas kucia. Analizę numeryczną wykonano z użyciem komercyjnego programu „DEFORM 3D”, składającego się z części mechanicznej, termicznej i prognozowania mikrostruktury. Porównanie teoretycznych i eksperymentalnych rezultatów badań wskazuje na dobrą ich zgodność.

EN

The article discusses the influence of the main parameters of the cogging process on distribution of the effective strain, mean stresses and temperature within the volume of forged material. Finite element method was employed to model plastic flow and heat transfer in the cogging process of tool steel in the skew surfaces anvils. This allowed the prediction of the microstructure evolution during hot forging. For the numerical modelling a commercial program DEFORM - 3D with thermo-mechanic and microstructural evolution coupled had been employed. Good agreement between theoretical and experimental results was observed.

18

Analiza procesu kucia wydłużającego ze skręcaniem

Kukuryk M.

Hutnik, Wiadomości Hutnicze

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2012

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Vol. 79, nr 11

801--804

PL

W pracy przedstawiono wyniki badań wpływu procesu kucia wydłużającego ze skręcaniem na kinematykę płynięcia metalu i jakość odkuwek. Zaprezentowano nową konstrukcję narzędzia kuźniczego oraz opracowano odpowiednią metodykę kucia, która prowadzi do silnej koncentracji dodatkowych odkształceń postaciowych, tzw. mikropasm ścinania. Analizę dla przestrzennego stanu odkształcenia oparto na rozkładzie intensywności odkształcenia i naprężenia, naprężeń średnich i temperatury. Rozwiązanie uzupełniono o model zmian mikrostruktury w czasie odkształcenia. Wyniki teoretyczne poddano weryﬁkacji eksperymentalnej.

EN

The paper presents results of the studies on the effect of application of the process of cogging with torsion on the kinematic of material ﬂow and quality of forgings. New construction of the forging tool as well as appropriate methodology leading to strong concentration of the additional non-dilatation strain, micro-shear bands have been presented. The analysis for three-dimensional state of strain was based on distribution of the effective strain and stress, mean stresses and temperature. This allowed the prediction of the microstructure evolution during forging. The results are compared with the experimental data.

19

Analiza numeryczna odkształceń oraz mikrostruktury podczas wysokotemperaturowego kucia wydłużającego stopu tytanu Ti-6Al-4V

Kukuryk M.

Inżynieria Materiałowa

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2011

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Vol. 32, nr 2

90-97

PL

W pracy przedstawiono analizę przestrzennego stanu odkształcenia dla procesu kucia wydłużającego stopu tytanu Ti-6Al-4V z wykorzystaniem metody elementów skończonych z założeniem sztywno-plastycznego modelu odkształcanego ciała. Przedstawiono wyniki prac związanych z symulacją schematu płynięcia metalu i zjawisk cieplnych w procesie odkształcania materiału w warunkach kucia na gorąco. Analizę numeryczną wykonano z wykorzystaniem programu DEFORM-3D, składającego się z części mechanicznej, termicznej i mikrostrukturalnej. Rezultaty obliczeń umożliwiają określenie rozkładu intensywności odkształcenia, intensywności naprężeń, naprężeń średnich i temperatury w objętości odkuwki. Rozwiązanie uzupełniono o model rozwoju mikrostruktury w czasie odkształcenia, który pozwala wyznaczyć rozkład wielkości ziarna i ułamka objętości materiału zrekrystalizowanego wewnątrz odkształcanych odkuwek. Wartości naprężenia uplastyczniającego dla stopu tytanu Ti-6Al-4V przyjmowano na podstawie przeprowadzonych badań plastometrycznych dla różnych wartości odkształceń, prędkości odkształceń i dla ustalonego zakresu temperatury przeróbki plastycznej na gorąco (?p = ?(?, ?˙, T)). Badania przeprowadzono w zakresie temperatury od 1023 K do 1373 K, przy czym ze wzrostem temperatury obserwowano obniżenie poziomu naprężenia uplastyczniającego. Doświadczalnie wyznaczone krzywe ?p = f(?) wykazują charakterystyczne maksimum naprężenia uplastyczniającego, które występuje przy odkształceniu nieco powyżej ?h = 0,20. Kucie przeprowadzono w kowadłach płaskich oraz w kowadłach specjalnych trójpromieniowych. Dla badanego stopu tytanu charakterystykę właściwości cieplnych, takich jak: gęstość, ciepło właściwe i przewodnictwo cieplne przyjęto na podstawie danych eksperymentalnych i zadawano jako funkcje temperatury. W pracy przedstawiono rozkład ułamka objętości zrekrystalizowanej dynamicznie i średniej wielkości ziarna na powierzchni poprzecznego przekroju próbki ze stopu tytanu Ti-6Al-4V podczas kucia wydłużającego w kowadłach płaskich. Rekrystalizacja dynamiczna rozpoczyna się w dużej części obszaru poddanego odkształceniu, a ułamek objętości zrekrystalizowanej dynamicznie podczas kucia na kowadłach płaskich osiąga swoje maksimum w środku odkuwki i wynosi 70% (dla gniotu 0,70). Dla powierzchni kontaktowych i bocznych ułamek objętości zrekrystalizowanej jest dużo mniejszy i wynosi 20%. Przewidywana wielkość ziarna jest najmniejsza w środku odkuwki i wynosi 24 ?m (dla gniotu 0,70) i 44 ?m dla powierzchni czołowych i bocznych odkuwki. Ze wzrostem odkształcenia obserwowano zmniejszanie wielkości ziarna. Zastosowane w badaniach kowadła specjalne trójpromieniowe wykazały korzystny wpływ na rozkład odkształceń i naprężeń w procesie kucia stopu tytanu Ti-6Al-4V. Największe wartości intensywności odkształcenia występują w obszarach odkuwki znajdujących się pod wypukłymi powierzchniami kowadeł (?i /?h = 1,44), środkowy obszar odkuwki doznaje mniejszych odkształceń (?i /?h = 0,97). Dużą zaletą kucia w tych kowadłach jest wysoka równomierność rozkładu intensywności odkształcenia. Analizą objęto również zmiany mikrostruktury podczas kucia w tych kowadłach. Podczas kucia w kowadłach specjalnych trójpromieniowych ułamek objętości zrekrystalizowanej dynamicznie osiąga swoje maksimum w obszarach odkuwki znajdujących się pod wypukłymi powierzchniami kowadeł i wynosi 65% dla gniotu 0,70. Dla środkowych części odkuwki jest mniejszy i wynosi 56%. Wielkość ziarna na powierzchni styku odkształcanego materiału z kowadłami trójpromieniowymi wynosi 20 ?m oraz 27,5 ?m dla strefy centralnej odkuwki i gniotu ?h = 0,70. Na podstawie otrzymanych wyników stwierdzono, że rozkład wielkości ziarna jest znacznie korzystniejszy w kowadłach trójpromieniowych w porównaniu z kowadłami płaskimi. Wyniki teoretyczne poddano weryfikacji eksperymentalnej.

EN

A three-dimensional rigid-plastic finite element (FEM) analysis has been performed to quantitatively describe the hot stretch forging process of Ti- -6Al-4V titanium alloy. Finite element method was employed to model plastic flow and heat transfer in the deformed material. For the numerical modelling a commercial program DEFORM-3D with thermomechanical and microstructural evolution coupled FEM code had been employed. The numerical calculation gave an assessment of the strain, strain rate, stress and temperature distributions in the workpiece. This allowed the prediction of the microstructure evolution during hot forging. A model was developed to predict grain size and recrystallized volume fraction during hot forging. The flow curve is determined as a function of strain, strain rate and temperature (?p = ?(?, ?˙, T)). The flow curves show the flow softening behavior in the temperature ranges of 1023 K and 1373 K, the extent of flow softening decreases to a lesser degree with an increase in temperature. In the present experiment, the peak stress was observed at true strain about 0.20. In the study, two pairs of anvils were used in the computer simulations and experimental tests of the stretch forging process: flat and assembly of three-radius anvils. Variation of the physical properties of workpiece for the Ti-6Al-4V titanium alloy as function of temperature. The distribution of dynamical recrystallized volume fraction and mean grain size from simulation in flat anvils, has been obtained. The fraction of dynamic recrystallization has been 70% (for the reduction of 0.70) at center region, and 20% at die contact region. Predicted grain size from simulation is 24.0 ?m (for the reduction of 0.70) at center region, and 44.0 ?m at die contact region. The recrystallized grain size decreased with increasing strain. For specimens deformed in the assembly of three-radius anvils the effective strain distribution was most uniform. After the second reduction values of local deformations in the range ?i /?h = 0.97 has been obtained in the central parts of specimen cross-section and in the ?i /?h = 1.44 in the external specimen layers. The distribution of dynamical recrystallized volume fraction and mean grain size from simulation in the assembly of three-radius anvils, has been obtained. The fraction of dynamic recrystallization has been 56% (for the reduction of 0.70) at center region, and 65% at die contact region. Predicted grain size from simulation is 27.5 ?m (for the reduction of 0.70) at center region, and 20 ?m at die contact region. Based on the results it can be stated that with the increase of relative reduction, the mean grain size decreases, maximal value of mean grain size has been observed for flat anvils and minimal for shape of three-radius anvils. The best results from the quality point of view has been obtained for three-radius anvils. The results of theoretical investigation were verified by experimental tests.

20

The effect of cryogenic treatment on the microstructure and mechanical properties of Cu46Zr46Al8 bulk metallic glass matrix composites

Ma G. Z., Chen D., Chen Z. H., Liu J. W., Li W.

Materials Science Poland

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2010

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Vol. 28, No. 2

595--601

EN

The influence of cryogenic treatment (CT) on the microstructure and mechanical properties of Cu46Zr46Al8 glassy matrix composite fabricated by the process copper of mould suction casting. The distribution and morphology of test samples of CuZr phase changed under CT. After CT, the second phase is distributed more homogenously, and the morphology was transformed from dendrites to plates. This change in the microstructure improved the mechanical properties of the composite. Although compression fracture was still the brittle mode, the compression fracture strength was improved greatly after CT. Due to the morphological changes, the microhardness was increased about 18.55% when the treatment time was 72 h.