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1

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.

2

The Investigation of Ground Granulated Blast Furnace Slag Geopolymer at High Temperature by Using Electron Backscatter Diffraction Analysis

Aziz Ikmal Hakem, Al Bakri Abdullah Mohd Mustafa, Salleh Mohd Arif Anuar Mohd, Yoriya Sorachon, Razak Rafiza Abd, Mohamed Rosnita, Baltatu Madalina Simona

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

227--231

EN

This paper elucidated the potential of electron backscatter diffraction analysis for ground granulated blast furnace slag geopolymers at 1000°C heating temperature. The specimen was prepared through the mechanical ground with sandpaper and diamond pad before polished with diamond suspension. By using advanced technique electron backscatter diffraction, the microstructure analysis and elemental distribution were mapped. The details on the crystalline minerals, including gehlenite, mayenite, tobermorite and calcite were easily traced. Moreover, the experimental Kikuchi diffraction patterns were utilized to generate a self-consistent reference for the electron backscatter diffraction pattern matching. From the electron backscatter diffraction, the locally varying crystal orientation in slag geopolymers sample of monoclinic crystal observed in hedenbergite, orthorhombic crystal in tobermorite and hexagonal crystal in calcite at 1000°C heating temperature.

3

A dislocation density-based model for the work hardening and softening behaviors upon stress reversal

Lisiecka-Graca Paulina, Bzowski Krzysztof, Majta Janusz, Muszka Krzysztof

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

721--731

EN

The mechanical behaviours of microalloyed and low-carbon steels under strain reversal were modelled based on the average dislocation density taking into account its allocation between the cell walls and cell interiors. The proposed model reflects the effects of the dislocations displacement, generation of new dislocations and their annihilation during the metal-forming processes. The back stress is assumed as one of the internal variables. The value of the initial dislocation density was calculated using two different computational methods, i.e. the first one based on the dislocation density tensor and the second one based on the strain gradient model. The proposed methods of calculating the dislocation density were subjected to a comparative analysis. For the microstructural analysis, the high-resolution electron backscatter diffraction (EBSD) microscopy was utilized. The calculation results were compared with the results of forward/reverse torsion tests. As a result, good effectiveness of the applied computational methodology was demonstrated. Finally, the analysis of dislocation distributions as an effect of the strain path change was performed.

4

EBSD characterization of bobbin friction stir welding of AA6082-T6 aluminium alloy

Tamadon A., Pons D. J., Clucas D.

Advances in Materials Science

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2020

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Vol. 20, nr 4(66)

49--74

EN

Electron Backscatter Diffraction (EBSD) was used to determine microstructural evolution in AA6082-T6 welds processed by the Bobbin Friction Stir Welding (BFSW). This revealed details of grain-boundaries in different regions of the weld microstructure. Different polycrystalline transformations were observed through the weld texture. The Stirring Zone (SZ) underwent severe grain fragmentation and a uniform Dynamic Recrystallisation (DRX). The transition region experienced stored strain which changed the grain size and morphology via sub-grain-boundary transformations. Other observations were of micro-cracks, the presence of oxidization, and the presence of strain hardening associated with precipitates. Flow-arms in welds are caused by DRX processes including shear, and low and high angle grain boundaries. Welding variables affect internal flow which affects microstructural integrity. The shear deformation induced by the pin causes a non-uniform thermal and strain gradient across the weld region, leading to formation of mixed state transformation of grain morphologies through the polycrystalline structure. The grain boundary mapping represents the differences in DRX mechanism I different regions of the weld, elucidates by the consequences of the thermomechanical nature of the weld. The EBSD micrographs indicated that the localised stored strain at the boundary regions of the weld (e.g. flow-arms) has a more distinct effect in emergence of thermomechanical nonuniformities within the DRX microstructure.

5

A combined full-field imaging and metallography approach to assess the local properties of gas tungsten arc welded copper–stainless steel joints

Saranarayanan R., Lakshminarayanan A. K., Venkatraman B.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 1

251--267

EN

The local material properties of gas tungsten arc welded (GTAW) C21000 grade copper alloy (Cu) to AISI 304 grade stainless steel (SS) joints using (ErNiCu-7) filler material are studied using a range of material characterization techniques. Electron Back Scattered Diffraction (EBSD) studies across the weld confirmed the relationships existing between the solidification modes (dendritic, planar) and their corresponding grain morphology in a high resolution. The SEM-Backscattered Electron Mode (BSE) integrated with Energy Dispersive Spectroscopy (EDS) analysis evidenced the local heterogeneous compositions across the dissimilar weld. The global and local mechanical performance of the weld joints are assessed using a conventional uniaxial tensile tests and full-field 2D-digital image correlation (DIC) respectively. The local material behaviour of the weld joint is in-line with the compositional and microstructural gradients. The weld joint has achieved the ultimate tensile strength (UTS) of 258 ± 14 MPa, which is very close to the strength of the Cu base metal (BM) and all the joints were fractured in the Cu-HAZ. Microhardness distributions measured using a spatially positioned indents found that the weld fusion zone (129.28 ± 19.22 HV) has higher hardness in compared to the Cu-BM (80.51 ± 2.58 HV).

6

Microstructure and Mechanical Properties of AA1050/ AA6061/AA1050 Multi-Layer Sheet Fabricated by Cold Roll Bonding Process

Lee S.-H.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1489--1492

EN

A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA1050 multi-layer sheet. Three Al sheets in which an AA6061 sheet is inserted inside two AA1050 sheets of 2 mm thickness, 40 mm width and 300 mm length were stacked up after surface treatment, and the material was then reduced to a thickness of 1.0 mm by multi-pass cold rolling. The AA1050/AA6061/AA1050 laminate complex sheet fabricated by roll bonding was then hardened by a natural aging (T4) and an artificial aging (T6) treatments. The microstructures of the as-roll bonded and the age-hardened Al complex sheets were revealed by optical microscope and electron back scatter diffraction analysis, and the mechanical properties were investigated by tensile and hardness testing. The strength of the as-roll bonded complex sheet was found to increase by 2.6 times, compared to that value of the starting material. Both AA1050 and AA6061 showed a typical recrystallization structure in which the grains were equiaxed after heat treatment. However, the grain size was smaller in AA6061 than in AA1050.

7

Effect of Crystalographic Texture on Cavitation Wear Resistance of As-Cast CuZn10 Alloy

Jasionowski R., Polkowski W., Zasada D.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

935--940

EN

Analysis of a crystallographic texture (a preferred orientation) effect on cavitation wear resistance of the as-cast CuZn10 alloy, has been conducted in the present paper. The experiment was conducted on the CuZn10 alloy samples with <101>//ND or <111>//ND preferred orientations (where the ND denotes direction that is perpendicular to the exposed surface). The cavitation resistance examinations have been carried out on three different laboratory stands (namely, vibration, jet-impact and flow stands) that are characterized by a various intensity and a way of cavitation’s excitement. Obtained results point towards a higher cavitation resistance of the CuZn10 alloy with the <111>//ND preferred orientation.

8

Effect of Local Strain Distribution of Cold-Rolled Alloy 690 on Primary Water Stress Corrosion Crack Growth Behavior

Kim S.-W., Ahn T.-Y., Lim Y.-S., Hwang S.-S.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1243--1248

EN

This work aims to study the stress corrosion crack growth behavior of cold-rolled Alloy 690 in the primary water of a pressurized water reactor. Compared with Alloy 600, which shows typical intergranular cracking along high angle grain boundaries, the cold-rolled Alloy 690, with its heterogeneous microstructure, revealed an abnormal crack growth behavior in mixed mode, that is, in transgranular cracking near a banded region, and in intergranular cracking in a matrix region. From local strain distribution analysis based on local mis-orientation, measured along the crack path using the electron back scattered diffraction method, it was suggested that the abnormal behavior was attributable to a heterogeneity of local strain distribution. In the cold-rolled Alloy 690, the stress corrosion crack grew through a highly strained area formed by a prior cold-rolling process in a direction perpendicular to the maximum principal stress applied during a subsequent stress corrosion cracking test.

9

Changes in Structure of CuCr0.6 Alloy After Repetitive Corrugation Process

Jung T., Kwaśny W., Rdzawski Z., Głuchowski W., Matus K., Pawlyta M., Szindler M.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

2441--2448

EN

This paper presents the study of repetitive corrugation process influence on the strengthening of annealed alloy. Based on the results of mechanical properties of deformed sample, it has been found that the microhardness, ultimate tensile strength, yield strength and apparent elastic limit are significantly increased in relation to annealed sample. Examination on transmission electron microscopy confirmed the effect of intensive plastic deformation on structure fragmentation in the nanometric scale. This work confirmed the possibility of using the repetitive corrugation process to increase mechanical properties of CuCr0.6 alloy.

10

Characterization Of An Equal Channel Angular Pressed Al-Zn-In Alloy

Banjongprasert C., Jak-Ra A., Domrong C., Patakham U., Pongsaksawad W., Chairuangsri T.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

887--890

EN

Equal channel angular pressing (ECAP) is a technique that creates a high accumulated strain in metals and results in ultrafine-grained structure. In this study, Al-5Zn-0.02In was processed by ECAP at a room temperature using route Bc through an ECAP die (press angle of Φ = 100° and Ψ = 20°). The samples were subjected to ECAP with 1, 2, 3 and 4 passes. The processed specimens were characterized using electron backscatter diffraction (EBSD). The results confirmed the grain refinement of the alloy after ECAP to an average grain size less than 5 μm after 4-pass ECAP. The microhardness test shows that the hardness increased with the number of passes. The hardness of the cross-sectional area of the sample was similar to that tested along the pressing direction.

PL

Metoda przeciskania w kanale kątowym (ang. Equal channel angular pressing; ECAP) prowadzi do powstania bardzo wysokich naprężeń, w wyniku czego otrzymuje się ziarna o bardzo drobnej strukturze. W niniejszej pracy, stop Al-5Zn-0,02In wytwarzano metodą ECAP w temperaturze pokojowej, wykorzystując ścieżkę Bc przez matrycę ECAP (kąty krzywizny: Φ = 100° i Ψ = 20°). Próbki poddano ECAP z 1, 2, 3 i 4 przejściami. Otrzymane próbki badano metodą dyfrakcji elektronów wstecznie rozproszonych (ang. electron back scatter diffraction; EBSD). W stopie otrzymanym metodą ECAP z 4 przejściami, średnia wielkość ziaren wynosiła mniej niż 5 μm. Badania mikrotwardości wykazały, że twardość zwiększała się wraz z liczbą przejść. Twardość zmierzona w poprzek próbki byłą porównywalna do tej mierzonej wzdłuż osi nacisku.

11

Phases identification by means of EBSD method - new possibilities of materials researches

Klimek L.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 1

151-155

EN

The examples of EBSD analysis of selected phases in steel are presented in this paper. The carbon steel, Co-Cr-Mo alloy and steel after termochemical treatment were examined. The obtained results confirm that the EBSD method can be a valuable tool used for recessive analysis of phases which occure in alloys with giving particular attention to theirs polymorphism and non stechiometry. It allows examining samples both as metallographic cross-section and fracturing as well as samples after surface treatment.

PL

W artykule przedstawiono przykładowe możliwości analizy składu fazowego materiałów. Badania wykonano na stopie Co-Cr-Mo, przełomie stali węglowej oraz stali po obróbce cieplnochemicznej. Z przytoczonych badań wynika, że dyfrakcja elektronów wstecznie rozproszonych może być cennym narzędziem służącym do precyzyjnej identyfikacji faz występujących w stopach z uwzględnienicm ich niestechiometryczności i polimorfizmu. Istnieje możliwość badan zarówno na zgładach nietalograficznych , powierzchniach po obróbkach cieplnochemicznych oraz przełomach.