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1

Adhesion of titanium coatings applied by cold spraying on selected metal substrates

Makrenek M.

Archives of Materials Science and Engineering

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2023

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Vol. 123, nr 2

49--54

EN

Purpose: Measurement of the adhesion of a Ti coating applied by cold spraying on metal substrates with different elastic modulus. An attempt to analytically describe the experimental results, considering cold gas spray parameters such as working gas, pressure p and temperature T. Design/methodology/approach: Ti coating was sprayed on flat bars made of metal: copper, magnesium, brass, titanium, Al 7075, Al 2024 and steel with dimensions of 4x50x400 mm. All coatings were applied under the same spray conditions (p = 3.8 MPa, T = 800ºC, spray distance l = 50 mm, and spray spead V = 400 mm/s). The state of plastic deformation of coatings and substrates was examined using optical methods, and the adhesion strength was measured with the POSITEST tester. Findings: The experimental results are presented graphically. The adhesion force as a function of the relative modulus of elasticity showed a maximum. At this time, the mutual penetration depth of the coating and the substrate showed a minimum. The extremes of the relationships mentioned above occurred for points where the relative modulus of elasticity took the value one. The curve described by formula (1) was fitted to the distribution of adhesion points as a function of the relative elastic modulus. The function parameter described by formula (1) is related to the spray parameters (p, T). Research limitations/implications: To achieve a better accuracy of the analytical description of the adhesion of coatings deposited with cold gas, tests should be carried out on a larger number of substrates. The validity of the presented interpretation should be checked by applying coatings from other materials. Practical implications: In coating technologies, adhesion is a key concept. A coating with high adhesion strength is used primarily in regeneration and anti-corrosion protection processes. The analytical relationship between adhesion, relative modulus of elasticity and cold gas spray parameters will significantly speed up the selection of optimal spray parameters. Cold spray technology is a cost-intensive technology, so the economic element is not without significance. Originality/value: The article presents a method for limiting the number of variables on which the quality of the applied coatings depends. The relationship between the adhesion force, the relative elastic modulus and the selected spray parameters are indicated.

2

Modeling and analysis of tangential force in robot abrasive belt grinding of nickel‑based superalloy

Zhang Weijian, Gong Yadong, Zhao Xianli, Xu Yunchao, Li Xiang, Yin Guoqiang, Zhao Jibin

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e124, 2023

EN

Grinding force directly affects the grinding equipment performance, the grinding tool wear, and the machined surface quality, and it is an important grinding performance indicator. In this paper, a tangential force prediction model is established for robot abrasive belt grinding (RABG) of nickel-based superalloy. According to the shape characteristics of grits and the interaction mechanism between grits and workpiece, the tangential components of cutting force and frictional force on the grits are determined. On this basis, the tangential force prediction model is established by the grit protrusion height distribution and the elastic contact theory. In addition, according to the wear characteristics of the structured abrasive belt, the expression of grit distribution density (i.e. the number of grits per unit area) is obtained and applied to the tangential force model. The force model is evaluated by the verification experiment, and the results show that it has good prediction ability. At the same time, this paper discusses the influence of grinding parameters on tangential force, and reveals the material removal characteristics of RABG of nickel-based superalloy based on the analysis of the tangential force and the morphology characteristics of grinding surfaces and chips.

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

Investigation of longitudinal bending distortion of a double-side edge welded fin plate by study of plastic zones

Sudharsanam V., Narayanan C. Sathiya, Shanmugarajan B., Prakash L.

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e88, 2023

EN

The Okerblom’s theory of double-side welded structures states that the resultant longitudinal bending distortion will not be zero in structures that are welded with equal heat input on both the sides of centre of gravity axis, on account of smaller plastically deformed zone near the second weld. However, investigations have not been performed thus far in exploring why such a phenomenon happens. This is the gap that this research work addresses. Accordingly, investigations were made by performing welding on both the edges of a rectangular fin plate using gas metal arc welding (GMAW) both by experimentation and by finite element (FE) simulation using SYSWELD software. Von Mises stress plots and transient strain plots of few elements near the first and second edge of the fin plate were analysed to study their relative influence in causing the plastic deformation of the elements. The analysis showed that the smaller size of the plastic zone formed near the second edge weld was mainly due to the presence of residual tensile strain on the second side elements, formed as result of the weld laid on the first edge of the fin plate.

5

Finite element analysis of material deformation behaviour during DRECE: the sheet metal SPD process

Tkocz Marek, Kowalczyk Karolina, Bulzak Tomasz, Jabłońska Magdalena B., Hawryluk Marek

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e145, 2023

EN

The material deformation behaviour during the innovative SPD process called DRECE (Dual Rolls Equal Channel Extrusion) has been analysed by FEM simulations. In the process, a workpiece in the form of a strip is subjected to plastic deformation by passing through the angular channel; however, the workpiece dimensions remain the same after a pass is finished. Performing consecutive passes allow for increasing the effective strain in the material to a required level. In the conducted simulations two various channel angles (108° and 113°) have been taken into consideration, as well as two processing routes, A and C (without and with turning the strip upside-down between consecutive passes, respectively). The analysis of simulation results has revealed that significant strain and stress inhomogeneities across the strip thickness are generated in a single DRECE pass. The die design (the inner and outer corner radius) and friction conditions affect the material flow, reducing significantly the shear strain in the near-surface regions of the strip. The strain inhomogeneity can be effectively reduced by choosing the processing route C. The strain distributions and the corresponding tensile test results have confirmed that the smaller channel die angle allows to generate larger strain and higher strength of the strip but also reduces its ductility more than the die setup with the larger channel die angle.

6

Effect of surface integrity on fatigue life of 7075‑T6 aluminum alloy by combination of fine turning with hydrostatic deep rolling

Zhou Yongxin, Chu Xingrong, Zang Shunlai, Sun Jiao, Yang Lei, Gao Jun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e41, 2023

EN

In this study, the 7075-T6 aluminum alloy sample was firstly prepared by fine turning(FT) process, and then the surface treatments were subjected to hydrostatic deep rolling(HDR), including constant pressure deep rolling(CPDR) and increasing pressure deep rolling(IPDR). Subsequently, the influence of surface integrity on the fatigue life of the 7075-T6 aluminum alloy is investigated by the combination of FT with HDR. The results show that the fatigue life of IPDR and CPDR samples is increased significantly by 148% and 450% compared to the FT sample in the tensile-compression fatigue test. The improved fatigue life of IPDR and CPDR samples is a result of reduced significantly surface roughness and the increase of surface compressive residual stress, surface micro-hardness and the depth of plastic deformation layer. In addition, the deeper plastic deformation layer is the main reason for the higher fatigue life of the CPDR sample than the IPDR sample.

7

Crystal plasticity elastic-plastic rate-independent numerical analyses of pollycrystalline materials

Wójcik Marta, Skrzat Andrzej, Stachowicz Feliks, Spišák Emil

Advances in Mechanical and Materials Engineering

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2023

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Vol. 40, nr 1

63--78

EN

Macroscopic analyses of plastic forming processes give only the overall description of the problem without the consideration of mechanisms of plastic deformation and the microstructure evolution. For the consideration of these processes, numerical simulations within crystal plasticity include the change of texture, anisotropy, and strain hardening of the material are used. In this paper, a crystal plasticity rate-independent model proposed by Anand and Kothari is applied for numerical analyses of polycrystalline materials. The slip was considered as the main mechanism of the plastic deformation. Basic constitutive equations of crystal plasticity for large deformation theories are presented. The selected results of elastic-plastic problems obtained using both macro- and micro- scales software for the explicit and implicit integration are featured here. The heterogeneous distribution of strain and stress in different grains are obtained, which is associated with the various crystal orientation. The crystal plasticity modelling of materials subject to plastic deformation involves not only the information about the change of a material’s shape in a macro-scale, but also describes the phenomena occurring in material in a micro-scale.

PL

Analizy makroskopowe procesów przeróbki plastycznej prezentują jedynie ogólny zarys rozważanego problemu, bez uwzględnienia mechanizmów odkształcenia plastycznego oraz ewolucji mikrostruktury. W celu rozważania procesów przeróbki plastycznej stosowane są symulacje numeryczne w ramach teorii plastyczności kryształów uwzgledniające zmianę tekstury, anizotropię oraz umocnienie odkształceniowe. W artykule zaprezentowano zastosowanie modelu Ananda i Kothari w ramach teorii plastyczności kryształów niezależnej od prędkości odkształcenia do rozwiązywania analiz numerycznych dla materiałów polikrystalicznych. W badaniach uwzględniono poślizg dyslokacyjny jako główny mechanizm odkształcenia plastycznego. Zaprezentowano wybrane rezultaty dla problemów sprężysto-plastycznych uzyskane zarówno w skali makro, jak i mikro- dla całkowania typu explicit i implicit. Uzyskano niejednorodny rozkład naprężenia i odkształcenia w poszczególnych ziarnach, związany z różną orientacją kryształów. Modelowanie numeryczne zzastosowaniem teorii plastyczności kryształów dla materiałów poddanych plastycznemu odkształceniu dostarcza nie tylko informacje o zmianie kształtu materiału w skali makro, ale także opisuje zjawiska zachodzące w materiale w skali mikro-.

8

Influence of multi extrusion die process on mechanical and chemical behavior of 2024-T3 alloy

Razooqi Ahmed Ibrahim, Abbas Naseer M., Ghazi Sara Saad

International Journal of Applied Mechanics and Engineering

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2022

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Vol. 27, no. 3

163--170

EN

In this paper, a cold multi-pass extrusion process for a 15mm in diameter solid 2024-T3 aluminum alloy rod was carried out using three dies to obtain three different diameters of 14mm, 13mm, and 12mm. The microstructure, hardness, and corrosion behavior were investigated before and after the extrusion process. Load-Displacement data were recorded during each extrusion process. The electrochemical corrosion test was made in a 3.5 wt.% NaCl solution using potentiostat instrument under static potentials test. Corrosion current was recorded to determine the corrosion rate for specimens. The results showed that the extrusion load increased with the number of extrusion passes, which is also seen in hardness test results. In addition, the corrosion rate decreased with the increase in the number of extrusion passes. This is due to severe plastic deformation, which generates a fine grain structure of (AlCu) and (AlCuMg) components.

9

An analysis of crystallographic texture and residual stresses of aluminium alloy RSA-501 after selected processes of twist extrusion (TE)

Byczkowska P., Sawicki J., Adamczyk-Cieślak B., Januszewicz B.

Archives of Materials Science and Engineering

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2022

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Vol. 118, nr 1

5--28

EN

Purpose: This study presents the residual stress analysis for the twist extrusion (TE) process after the experiment and numerical simulation and the analysis of the crystallographic texture changes and changes in hardness before and after the TE process for an RSA-501 aluminium alloy (Al; Mg5%; Mn1.5%; Sc0.8%; Zr0.4%). Design/methodology/approach: Crystallographic textures were obtained with the PANAlytical Empyrean X-ray diffractometer. The stresses were measured by applying the X-ray method with the use of using the PROTO iXRD diffractometer. Findings: The use of severe plastic deformation processes in the mass of the material leads to a significant change difference in the stress distribution in the workpiece and a change in texture compared to the reference material. The stress distribution in the sample cross-section and stress values varied and depended on the stage of the twisting process to which the surface was subjected. The highest stress (about 600 MPa) appears at the peaks of the front surface when exiting the twist area die TE. Higher stress values at the edges of the specimen are caused by friction (deformation) of the material against the die surface. The TE process strengthened – the highest crystallographic texture background level was 49%. Practical implications: The conducted tests and the obtained results allow the determination of the process parameters and critical areas of the sample by carrying out a numerical simulation. Originality/value: Microhardness increases due to the TE process and the largest values were observed at the edges. This phenomenon is confirmed by the numerical simulation results presented in this paper.

10

Superplasticity of high-entropy alloys: a review

Motallebi Reza, Savaedi Zeinab, Mirzadeh Hamed

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e20, 2022

EN

High-entropy alloys (HEAs) are a new class of engineering materials with unique mechanical and functional properties. Superplastic forming of HEAs might be a viable route for actual applications of these alloys. Accordingly, the superplastic behaviors of HEAs and medium-entropy alloys (MEAs) were summarized in this monograph, along with reviewing the basics of high-entropy alloys and fine-grained superplasticity. Moreover, the HEAs were introduced and the phase formation rules were discussed. Furthermore, the influences of grain refinement (by thermomechanical processing and severe plastic deformation (SPD) methods) and deformation conditions (temperature and strain rate) with special attention to the high strain rate superplasticity were summarized. The significance of thermal stability of the microstructure against grain coarsening was noticed, where the effects of multi-phase microstructure, formation of pinning particles, and favorable effects of the addition of alloying elements were explained. The effects of deformation temperature and strain rate on the thermally activated grain boundary sliding (GBS), precipitation of secondary phases (especially the Cr-rich σ phase), dissolution of phases, deformation-induced (dynamic) grain growth, partial melting, and dynamic recrystallization (DRX) were discussed for different HEAs and MEAs. The final part of this overview article is dedicated to the future prospects and research directions.

11

Effect of the number of passes on grain refinement, texture and properties of DC01 steel strip processed by the novel hybrid SPD method

Kowalczyk K., Jabłońska M. B., Tkocz M., Chulist R., Bednarczyk I., Rzychoń T.

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e115

EN

Dual rolls equal channel extrusion (DRECE) is an unconventional severe plastic deformation (SPD) process that can effectively produce the ultrafine-grained microstructure in metals and alloys. Previously, the DRECE process carried out on non-ferrous alloys and low-carbon steels were mostly focused on the influence of process parameters on the mechanical properties. The aim of this study was the evolution of the microstructure and texture in the DC01 low-carbon steel strip after the subsequent passes of the DRECE process. The scanning transmission electron microscope and scanning electron microscope equipped with an electron backscattering diffraction detector were used for microstructure investigations. Observations after selected DRECE passes revealed defected microstructure, characteristic for the materials after SPD processes, in the form of numerous dislocation tangles, systems with dense dislocation walls and dislocation cell blocks. The texture analysis showed that with the increase of strain, the rolling texture has weakened in the tested material. These changes were accompanied by the microhardness rise.

12

The decisive impact of microstructure on the machinability of pure copper

Sun Xiaoxiang, Ebrahimi Mahmoud, Attarilar Shokouh

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

852--860

EN

Ultrafine-grained (UFG) materials have been of great attention due to their considerable behavior compared to coarse-grained counterparts. Also, the machinability of these UFG materials is of great importance because of the machining significance in manufacturing the final shape of industrial components. Hence, this study dealt with machinability in relation to the microstructure and mechanical properties of the UFG pure copper processed by the twist extrusion. The remarkable microstructure evolution through the dynamic recrystallization mechanisms improved the tensile strengths and hardness of the twist extrusion processed pure copper. Also, the reduction of ductility in the UFG copper compared to the initial state was related to the change of tensile fractography mechanism in which the large and deep dimples transformed into the combined small and shallow dimples with some cleavage planes in the UFG copper. Furthermore, the enhanced machinability of the processed sample was related to its lower thermal conductivity and the development of strain localization within the narrow shear bands which lead to the production of discontinuous short chips. Hence, the formation of the UFG structure is a suitable option to attain the enhanced machinability behavior of copper as one of the most used metals.

13

Processing of commercially pure copper tubes by hydrostatic tube cyclic extrusion–compression (HTCEC) as a new SPD method

Eftekhari M., Faraji G., Bahrami M.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

595--606

EN

In this study, severe plastic deformation (SPD) process of hydrostatic tube cyclic extrusion–compression (HTCEC) was performed through two passes on the commercially pure copper tubes with the purpose of fabricating relatively long ultrafine-grained (UFG) tubes. In HTCEC process, the presence of pressurized hydraulic fluid around the piece plays a key role in the reduction of the friction load and, consequently, in the reduction of required pressing load. In principle, this facilitates the production of long and large tubes. After processing by HTCEC, the mechanical characteristics and microstructure evolution were examined. Microstructure analysis revealed that after the first pass of HTCEC process, an ultrafine cell microstructure with an average size of ~ 993 nm was attained. After two passes of HTCEC, the average size of cells/subgrains was reduced to ~ 340 nm. This was while the average grain size of the annealed sample was 41 μm. Also, after two passes of HTCEC process, a remarkable increase in the yield strength from 154 to 336 MPa, and the ultimate strength from 223 to 414 MPa was observed. Furthermore, the mean value of microhardness increased from 74 to 149 HV, and a more uniform distribution of microhardness along the thickness was seen, compared to the first pass of HTCEC. Meanwhile, unlike most conventional SPD methods, the value of elongation to failure was slightly lessened from 59.5 to 41.6%. SEM fractography analysis denoted that mostly ductile fracture occurred in the HTCEC-processed samples. In general, two main advantages of HTCEC process can be the production of relatively long ultrafine-grained tubes and the significant increase in the strength and hardness besides a low loss of ductility.

14

Microstructure and mechanical properties of the AA7075 tube fabricated using shear assisted processing and extrusion (ShAPE)

Nazari Tiji Sobhan A., Asgharzadeh Amir, Park Taejoon, Whalen Scott A., Reza-E-Rabby Md, Eller Michael, Pourboghrat Farhang

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

85--94

EN

Shear-assisted processing and extrusion (ShAPE) experimental setup and tooling were adopted for extruding thin-walled AA7075 aluminum tube from as-cast non-homogenized billet material in a single run. The mechanical and microstructural characterizations were performed on the as-extruded tube through tensile, hardness, electron backscatter diffraction (EBSD), and energy dispersive spectroscopy (EDS) tests. The results showed that the ShAPE process developed a significantly refined microstructure with uniform and almost equiaxed grain structure on both hoop and axial cross-sections of the extrudate as well as through the thickness of the material. The pole figures and inverse pole figures of the EBSD data showed a strong shear texture development, and it was found out that axial shear is the dominant deformation mechanism in the regions near the inner surface of the tube, while combined axial and torsional shears are the two dominant modes of deformation near the outer surface of the extrudate. As for the mechanical properties, there was an increase of 150 and 73% in the yield and ultimate strengths of the tube produced using ShAPE process, respectively, and an 18% decrease in maximum uniform plastic elongation compared to the conventionally extruded AA7075-O tube.

15

Mechanical and thermal stability of retained austenite in plastically deformed bainite-based TRIP-aided medium-Mn steels

Kozłowska Aleksandra, Grajcar Adam, Janik Aleksandra, Radwański Krzysztof, Krupp Ulrich, Matus Krzysztof, Morawiec Mateusz

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

807--820

EN

Advanced medium-Mn sheet steels show an opportunity for the development of cost-effective and light-weight automotive parts with improved safety and optimized environmental performance. These steels utilize the strain-induced martensitic transformation of metastable retained austenite to improve the strength–ductility balance. The improvement of mechanical performance is related to the tailored thermal and mechanical stabilities of retained austenite. The mechanical stability of retained austenite was estimated in static tensile tests over a wide temperature range from 20 °C to 200 °C. The thermal stability of retained austenite during heating at elevated temperatures was assessed by means of dilatometry. The phase composition and microstructure evolution were investigated by means of scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and transmission electron microscopy techniques. It was shown that the retained austenite stability shows a pronounced temperature dependence and is also stimulated by the manganese addition in a 3–5% range.

16

Experimental and modelling study of the grain refinement of Fe-30wt%Ni-Nb austenite model alloy subjected to severe plastic deformation process

Svyetlichnyy D. S., Majta J., Kuziak R., Muszka K.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

339--352

EN

This study addresses some aspects regarding a computer modelling based on three-dimensional Frontal Cellular Automata (FCA) for the simulation of ultrafine-grained (UFG) microstructure development in purpose-designed microalloyed austenite model alloy i.e. FCC structure. Proposed in the present study model is a step forward towards understanding the deformation and microstructure development mechanisms occurring during severe plastic deformation (SPD) processes with high accumulation of the plastic deformation effects in FCC structures. The analysed microalloyed austenite microstructures were developed due to SPD effects. Using the proposed computer model, based on three-dimensional FCA it has been shown that it is possible to predict some characteristics of the FCC microstructures such as the grain size and the distribution of the boundaries misorientation angle. These abilities were proved by the qualitative and quantitative comparisons of the modelling and SEM/EBSD results. The capabilities of the proposed model were tested using experimental results of the wire drawing processes. The paper presents the new original results of experimental studies of multi-staged MaxStrain technology with the microscopic investigation. Basing on data obtained from these studies, the dependencies of the evolution of grain structure and misorientation angle on the accumulative strain and cycle number were obtained in a form of approximation equations. The equations were implemented into the CA model, and MaxStrain technology was simulated. Comparison of the results obtained in experimental studies and simulations shows a satisfactory agreement. Industrial verification of the developed model as well shows a satisfactory agreement.

17

Effects of processing temperature and number of passes on the microstructure and mechanical properties of AA 6063 processed by cyclic expansion extrusion

Babu V., Shanmugavel Balasivanandha Prabu, Padmanabhan K. A.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

632--648

EN

The effects of the working temperatures (260 °C, 200 °C and 130 °C) on microstructure formation in the AA 6063 alloy, processed upto ten passes by cyclic expansion extrusion (CEE) was studied. The microstructures of the CEE-processed specimens in the convergent and extrusion regions (center and edge) were examined after every two passes. The EBSD analysis revealed a decrease in the average grain size from 22 ± 5 µm to 2 ± 0.5 µm after four passes, with a simultaneous presence of a large fraction of HAGBs (45%) at 130 °C processing temperature. The TEM observations also confirmed the presence of nano-grains of sizes in the range of 50–100 nm. The CEE-processed specimen showed the highest improvement in hardness and ultimate tensile strength from 38 ± 3.4 HV and 118 ± 6 MPa to 122 ± 1 HV and 267 ± 2 MPa, respectively, after four passes at 130 °C. The specimens processed at 260 °C (ten passes), and 200 °C (four passes) showed moderate improvement in strength of 184 ± 3 MPa and 216 ± 3 MPa, respectively. On further straining (at 200 °C and 130 °C after six to ten passes), continuous dynamic recovery and dynamic re-crystallization took place which led to grain growth during SPD and, as a result, the alloy lost its strain hardening capacity and there was a decrease in the mechanical properties. At higher number of passes, the grains were elongated and coarsened, i.e., a non-equiaxed microstructure was seen after ten passes at 200 °C and 130 °C. In contrast, the specimen processed at 260 °C after ten passes, showed a homogeneous microstructure with near-equiaxed grains with 38% of HAGBs. A lower processing temperature produced a microstructure with a fine grain size distribution after a lower number of passes.

18

Adiabatic shearing mechanism on Al-4.2%Cu alloy bars subjected to electromagnetic loading

Zhang Xu, Huang Yunkai, Meng Shengfei, Zhu Congcong, Li Guangyao, Cui Junjia

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

393--405

EN

This paper proposed an electromagnetic loading process with the high-speed impact. Al-4.2% Cu alloy bars were used to employ electromagnetic impact (EI) experiments. Deformation mechanism and microstructure evolution of EI samples were revealed by theoretical model and microstructure characterizations. The EI process had impact force (peak value 40 kN) and impact velocity (peak value 6.7 m/s) during a short time period (1.25 ms). Adiabatic shearing mechanism dominated the whole deformation process, causing that significant microstructure characteristic was adiabatic shear bands (ASBs). The theoretical analysis implied that the formation of ASBs was accounted for the radial velocity gradient. Most plastic deformations concentrated in ASBs, and approximately pure shear deformations resulted in adiabatic temperature rise of 0.33–0.42 Tm inside ASBs. The width of ASBs was about 135 μm, in which original equiaxial grains were elongated into laminated sub-structures. TEM observations showed multi-slip systems were simultaneously actuated due to severe shear deformations. High dislocation density and dislocation tangles distributed with the ASBs. Adiabatic temperature rise and distorted energies drove sub-grains rotate into recrystallization grains (70–280 nm) with large angle grain boundaries. The needed maximum time (45 μs) for rotational dynamic recrystallization was far less than that of plastic deformation, indicating that rotational dynamic recrystallization mechanism contributed to the formation of recrystallization grains.

19

Correlation between Tensile Deformation Behavior and Microstructural Morphology of Nuclear Grade Austenitic Stainless Steel Welded Joints using Infrared Thermography Technique

Rajasekaran R., Lakshminarayanan A. K., Menaka M.

Welding Technology Review

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2020

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R. 92, nr 1

7--15

EN

Tensile deformation behavior of nuclear grade Austenitic Stainless Steel (SS) and its welded joints fabricated by Gas Tungsten Arc Welding (GTAW) and Activated Flux Gas Tungsten Arc Welding (AGTAW) processes were studied and correlated with relevant microstructural morphologies using Infrared Thermography (IRT) technique. The microstructure of base metal showed a complete austenite phase. GTAW Fusion Zone (FZ) exhibited both primary ferrite and primary austenite mode of solidification. Meantime, AGTAW FZ exhibited only primary austenite mode of solidification. A strain rate of 4.4x10-4 s-1 was used during the tensile test of the base metal and welded joints. The failure locations of the base metal, GTAW and AGTAW samples were noticed at the center of the gauge portion, the base metal side away from Fusion Line (FL) and Heat Affected Zone (HAZ) respectively. The temperature variations of the base metal and weld zones were recorded in the form of thermograms using the IR camera at the different stages of the tensile deformation. During deformation study, peak temperature of 39.2 °C, 38.8 °C and 34 °C were observed at the base metal, GTAW and AGTAW samples respectively. The lesser peak temperature of the AGTAW sample compared to the base metal and GTAW samples indicated that the AGTAW sample undergone lesser deformation. Moreover, tensile deformation behaviours of the base metal and welded joints were correlated with their microstructural morphologies using corresponding temperature curves.

PL

W pracy zbadano zachowanie deformacji podczas rozciągania austenitycznej stali nierdzewnej i jej połączeń spawanych wykonanych metodą GTAW (Gas Tungsten Arc Welding) oraz AGTAW (Activated Flux Gas Tungsten Arc Welding), a następnie skorelowano je z odpowiednimi morfologiami mikrostrukturalnymi za pomocą termografii w podczerwieni (ang. lnfrared Thermography). Mikrostruktura materiału bazowego wykazała całkowitą fazę austenitu. Spoina GTAW wykazywała zarówno ferryt, jak i austenit, podczas gdy spoina AGTAW wykazywała jedynie austenit. Podczas próby rozciągania materiału bazowego i złączy spawanych zastosowano prędkość odkształcania o wartości 4,4x10-4 s-1. Do zerwania poszczególnych próbek doszło odpowiednio na środku próbki materiału bazowego, w linii wtopienia złącza spawanego GTAW i w strefie wpływu ciepła (SWC) złącza spawanego AGTAW. Zmiany temperatury w materiale rodzimym i poszczególnych obszarach złączy spawanych rejestrowano w formie termogramów za pomocą kamery na podczerwień, przy różnych etapach deformacji podczas rozciągania. Podczas badań odkształceń zaobserwowano maksymalne wartości temperatury: 39,2 °C, 38,8 °C i 34 °C odpowiednio w próbkach z materiału bazowego, spawanych GTAW i spawanych AGTAW. Niższa maksymalna temperatura próbki spawanej metodą AGTAW w porównaniu z pozostałymi próbkami wskazała, że uległa ona mniejszemu odkształceniu. Ponadto zachowania deformacji przy rozciąganiu materiału rodzimego i złączy spawanych zostały skorelowane z obrazami ich mikrostruktur przy użyciu odpowiednich krzywych temperatur.

20

Identification of plastic deformations in carbon steel elements using the filtered Barkhausen Noise signal

Dybała Jacek, Nadulicz Krzysztof

Vibrations in Physical Systems

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2020

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Vol. 31, nr 1

art. no. 2020106

EN

The paper presents new approach to processing the Barkhausen Noise signal in order to detect and identify plastic deformations in carbon steel. A new automatic method of Barkhausen effect signal filtration was investigated. Apart from a classical measurement of Barkhausen effect signal, for which the RMS value is assumed, the signal waveform factor was also used in analyzes. The developed approach to processing the Barkhausen Noise signal has made it possible to obtain more useful diagnostic data than those obtained from the raw signal.