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1

Precise Orientation Control of Single Crystalline NiMnGa-Based Alloys by in-situ EBSD Analysis

Szewczyk Arkadiusz, Faryna Marek, Wójcik Anna, Maziarz Wojciech, Chulist Robert

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

1171--1175

EN

The article presents a precise method for the orientation process of NiMnGa-based single crystals. For this method, a scanning electron microscope equipped with an EBSD camera and a heating stage allowing temperatures exceeding 873 K was used. The orientation process was carried out in both the high-temperature austenite phase and in the room-temperature martensite phase. The facilities allowed for determining the orientation of a single grain of austenite at elevated temperatures as well as the orientation of particular martensitic variants at room temperature. A practically perfect cubic orientation was obtained in the austenitic case with a deviation of about 1° while the samples oriented in the martensitic phase deviated from the desired orientation by 4.5-5.2°. Additionally, the training process of single crystals was carried out in order to show the influence of the orientation process on twinning stress.

2

Investigation of the Microstructure and Strengthening Mechanisms of Ti-6Cu-8Nb-xCr3C2 Alloy through Vacuum Sintering Process

Chang Shih-Hsien, Weng Chen-Yu, Huang Kuo-Tsung, Liang Cheng

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 3

815--825

EN

This study mixes four different powders to produce Ti-6Cu-8Nb-xCr3C2 (x = 1, 3, and 5 mass%) alloys in three different proportions. The experimental results reveal that when 5 mass% Cr3C2 was added to the Ti-6Cu-8Nb alloys, the specimen possessed optimal mechanical properties after sintering at 1275°C for 1 h. The relative density reached 98.23%, hardness was enhanced to 67.8 HRA, and the transverse rupture strength (TRS) increased to 1821.2 MPa, respectively. The EBSD results show that the added Cr3C2 in situ decomposed into TiC and NbC during the sintering process, and the generated intermetallic compounds (Ti2Cu) were evenly dispersed in the Ti matrix. Furthermore, the reduced Cr atom acts as a β-phase stabilizing element and solid-solution in the Ti matrix. Consequently, the main strengthening mechanisms of the Ti-6Cu-8Nb-xCr3C2 alloys include dispersion strengthening, solid-solution strengthening, and precipitation hardening.

3

The qualitative-quantitative approach to microstructural characterization of nanostructured bainitic steels using electron microscopy methods

Królicka Aleksandra, Janik Aleksandra, Żak Andrzej, Radwański Krzysztof

Materials Science Poland

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2021

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Vol. 39, No. 2

188-199

EN

Both qualitative and quantitative analyses play a key role in the microstructural characterization of nanobainitic steels focused on their mechanical properties. This research demonstrates various methods of microstructure analysis using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) techniques, taking into account these two approaches. The structural constituents have been qualitatively characterized using TEM and selected area electron diffraction (SAED), together with quantitative analysis based on the misorientation angle (EBSD). Besides, quantitative measurement of austenite with both blocky and film-like morphologies has been carried out. Due to the scale of nanostructured bainite, it is also important to control the thickness of bainitic ferrite and film-like austenite; hence, a method for measuring their thickness is presented. Finally, the possibility of measuring the prior-austenite grain size by the EBSD method is also demonstrated and compared with the conventional grain boundary etching method. The presented methods of qualitative and quantitative analyses form a complementary procedure for the microstructural characterization of nanoscale bainitic steels.

4

Effect of heat treatment on the microstructure and mechanical properties of a low-carbon X80 pipeline steel

Acosta-Cinciri B. C., López-Granados N. M., Ramos-Banderas J. A., Hernández-Bocanegra C. A., Garnica-González P., López-Corpus J. A.

Materials Science Poland

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2021

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Vol. 39, No. 1

103--112

EN

In this work, the effect of heat treatment conditions on the microstructure and mechanical properties of an American Petroleum Institute (API) X80 steel with a low carbon content of ~0.02% wt., destined for the manufacture of pipelines and pipeline transmission systems by welding, was investigated. Samples were heat treated under different conditions and then were characterized by scanning electron microscopy (SEM), orientation image microscopy (OIM), and electron backscattered diffraction (EBSD). The results showed that when the steel is fastly cooled from the austenitic field (990°C), the mechanical properties increase significantly [ultimate tensile strength (UTS) >1,100 MPa, yield strength (YS) 900 MPa, and elongation 27%] due to the high percentage of martensite (M) present in the microstructure (95%). In contrast, when the cooling rate decreases and the treatment conditions remain at/or above the bainitic/martensitic transformation (from 990°C to 600°C and 450°C), the mechanical properties are decreased by almost 50% because of the decrease in the percentage of martensite (18%). However, the percentage of elongation increases significantly (38%) due to the presence of other micro-constituents resulting from the phase transformation. On the other hand, the best combination of mechanical properties (UTS above 800 MPa and YS between 610 MPa and 720 MPa) was obtained when the steel acquired a dual-phase microstructure [(martensite/austenite)-(ferrite/martensite)] since the amount of martensite is conserved between 45% and 82%, in combination with the other micro-constituent present in the steel that allows us to achieve elongation percentages close to 30%.

5

Study of Extrusion Temperature on Extrudability of Al-Zn-Cu Based Alloy

Kim Yong-Ho, Yoo Hyo-Sang, Lee Kyu-Seok, Lee Sung-Ho, Son Hyeon-Taek

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1307--1310

EN

In this study, the extrusion characteristics of Al-2Zn-1Cu-0.5Mg-0.5RE alloys at 450, 500, and 550°C were investigated for the high formability of aluminum alloys. The melt was maintained at 720°C for 20 minutes, then poured into the mold at 200°C and hot-extruded with a 12 mm thickness bar at a ratio of 38:1. The average grain size was 175.5, 650.1, and 325.9 μm as the extrusion temperature increased to 450, 500 and 550°C, although the change of the phase fraction was not significant as the extrusion temperature increased. Cube texture increased with the increase of extrusion temperature to 450, 500 and 550°C. As the extrusion temperature increased, the electrical conductivity increased by 47.546, 47.592 and 47.725%IACS, and the tensile strength decreased to 92.6, 87.5, 81.4 MPa. Therefore, the extrusion temperature of Al extrusion specimen was investigated to study microstructure and mechanical properties.

6

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.

7

Stabilization of the cubic γ-U structure in U-T alloys (T = Mo, Pt, Nb, Ru, Ti)

Sowa Sylwia, Kim-Ngan Nhu-Tarnawska Hoa, Krupska-Klimczak Magdalena, Buturlim Volodymyr, Drozdenko Daria, Minarik Peter, Havela Ladislav

Journal of Machine Construction and Maintenance - Problemy Eksploatacji

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2019

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no. 1

39--46

EN

We present the results of the stabilization of the γ-U phase with a cubic structure in U-T alloys by means of combined ultrafast cooling (with a cooling rate 106 K/s) and doping with alloying elements in the VI and VIII group (T = Mo, Pt, Nb, Ru, Ti). The X-ray diffraction data have confirmed the cubic structure presented in all U-T alloys with the alloying element content T≥15 at.% (atomic percentage concentration). Some results of the microstructure analysis, phase distribution and orientation of selected samples by using electron backscatter diffraction are also shown.

PL

Zaprezentowaliśmy wyniki stabilizacji fazy γ-U ze strukturą kubiczną w związkach U-T za pomocą techniki ultraszybkiego chłodzenia (z szybkością chłodzenia 106 K/s) oraz domieszkowania pierwiastkami z grup VI i VIII (T= Mo, Pt, Nb, Ru, Ti). Dane dyfrakcji rentgenowskiej potwierdziły obecność kubicznej struktury we wszystkich związkach U-T posiadających zwartość pierwiastków domieszkujących T≥15 at.% (procent atomowy). Wyniki analizy mikrostruktury, rozkładu fazowego i orientacji wybranych próbek zostały również pokazane, używając dyfrakcji wstecznego rozpraszania elektronów.

8

Maps of crystal lattice orientation in polyphase microregions as a parameter of the microstructure image of a multicomponent metal alloy

Warmuzek Małgorzta, Polkowska Adelajda

Journal of Applied Materials Engineering

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2019

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Vol. 59, no. 3

127--136

EN

This study includes the results of tests related to selecting the data collection parameters for EBSD analysis, correction and modification of the EBS diffraction patterns, and use of selected functionalities of the commercial OIM system. The study also shows the local misorientation range and the local relationships of the crystal lattice orientation at interfaces and grain boundaries, estimated in the polyphase microregions of selected AlFeMnSi alloys.

9

Effect of Nb and Ti micro-additives and thermo-mechanical treatment of high-manganese steels with aluminium and silicon on their microstructure and mechanical properties

Sozańska-Jędrasik L., Mazurkiewicz J., Borek W., Matus K., Chmiela B., Zubko M.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 1

133--142

EN

The results are based on two experimental high-manganese X98MnAlSiNbTi24-11 and X105MnAlSi24-11 steels subjected to thermo-mechanical treatment by hot-rolling on a semi-industrial processing line. The paper presents the results of diffraction and structural studies using scanning and transmission electron microscopy showing the role of Nb and Ti micro-additives in shaping high strength properties of high-manganese austenitic-ferritic steels with complex carbides. The performed investigations of two experimental steels allow to explain how the change cooling conditions after thermo-mechanical treatment of the analysed steels affects the change of their microstructure and mechanical properties. The obtained results allow assessing the impact of both the chemical composition and the applied thermo-mechanical treatment technology on the structural effects of strengthening of the newly developed steels.

10

Tensile behavior, microstructure, and substructure of the friction stir welded 70/30 brass joints: RSM, EBSD, and TEM study

Heidarzadeh Akbar

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 1

137--146

EN

The effect of bead on plate friction stir welding parameters on the tensile properties of the 70/30 brass joints was investigated using response surface method. The microstructures of the joints were characterized using optical microscopy, electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM). The tensile test was conducted to measure the ultimate tensile strength and elongation of the joints. In addition, the fracture surfaces of the tensile specimens were analyzed by scanning electron microscopy (SEM). The results showed that the most effective parameters on the strength and elongation of the joints were tool rotational speed and axial force, respectively. Optimizing the parameters revealed that the maximum strength and elongation of 318.5 MPa and 54.9% can be achieved at a rotational speed of 1000 rpm, a traverse speed of 58.4 mm/min, and an axial force of 3 kN. The strengthening mechanisms of grain boundary and dislocation density effects were responsible for the higher ultimate tensile strength of the joints welded at the lower heat input conditions. Furthermore, the effect of friction stir parameters on the ultimate tensile strength and elongation of the joints has been discussed, thoroughly.

11

Microstructure, grain refinement and hardness of Al–3%Mg aluminium alloy processed by ECAP with helical die

Snopiński Przemysław, Tański T., Matus K., Rusz S.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 2

287--296

EN

In the present research, commercial Al–3%Mg aluminium alloy was subjected to the ECAP processing using a modified die with a helical 30° exit channel. The changes in microstructure were characterized by light microscopy, electron backscatter diffraction (EBSD) and TEM. Mechanical properties were compared based on hardness measurement. It is also shown that such modification of ECAP die enhances grain refinement due to the vortex-like flow of metal during subsequent deformations. The results of the metallographic study showed that microstructure is refined due to the interactions and intersections of the deformation bands. The mechanical properties examinations display a significant improvement after the first ECAP pass and less significant increase with subsequent passes.

12

Microstructure and strengthening model of Al-3%Mg alloy in a heat treated state subjected to ECAP process

Snopiński P.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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Vol. 90, nr 1

5--10

EN

Purpose: The aim of this paper is to investigate the microstructure evolution of a heat treated Al-3%Mg aluminium alloy subjected to the ECAP (equal channel angular pressing process). Design/methodology/approach: Commercial Al-3%Mg alloy subjected to the solution treatment followed by an artificial aging was subjected to the 6 ECAP passes using a processing route Bc. Then the microstructure investigations using a light microscopy, scanning electron microscopy and transmission electron microscopy were carried out. Additionally the XRD technique was used to calculate lattice micro strain and dislocation density. Findings: The experimental results showed that the obtained microstructure is refined by mutual interactions of shear and microshear bands. The TEM investigation revealed typical for deformed aluminium alloys structure constituents such as dislocation-free grains, nonequilibrium grain boundaries, dislocation cell and (sub)grain structures. Research limitations/implications: The presented investigation results were carried out on samples, not on final products. Practical implications: Current research is moving towards to develop high strength material having a ultra-fine grained microstructure and increased mechanical strength. Originality/value: The paper focuses on the microstructure characterization of ECAP processed Al-3%Mg aluminium alloy. The relationship between the obtained microstructure and its contribution to the Yield strength is investigated.

13

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.

14

Carbides Analysis of the High Strength and Low Density Fe-Mn-Al-Si Steel

Sozańska-Jędrasik L., Mazurkiewicz J., Borek W., Matus K.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

265--276

EN

The work presents the results of investigations into the structure and phase composition of newly developed high manganese steels of the X98MnAlSiNbTi24-11 and X105MnAlSi24-11 type. The average density of such steels is 6.67 g/cm3, which is 15% lower as compared to typical structural steels. An analysis of phase composition and structure allows to conclude that the investigated steels feature an austenitic γ-Fe(Mn,Al,C) structure with uniformly distributed and elongated α-Fe(Mn,Al) ferrite grains on the boundaries of austenite grains and carbides. Examinations by diffraction of back scattered electrons (EBSD) allow to conclude that high-angle boundaries dominate in such steels, having significant influence on mechanical properties. Three types of carbides with differentiated chemical composition and size were identified in steel X98MnAlSiNbTi24-11 with scanning and transmission electron microscopy. κ-(Fe,Mn)3AlC carbides, having a regular, face-centered cubic lattice (fcc), were identified in austenite. Transmission electron microscopy examinations have enabled to identify M7C3-type carbide in ferrite. Nb- and Ti-based complex carbides were identified in steel X98MnAlSiNbTi24-11, both, in ferrite and austenite. (NbTi)C2 carbide precipitates were confirmed in an X-ray qualitative phase analysis. The size of the above-mentioned carbides is within several to several dozens of μm. An X-ray qualitative phase analysis has confirmed the precipitates of M7C3 carbides in both steels.

15

Influence of heat treatment on the formation of ultrafine-grained structure of Al–Li alloys processed by SPD

Rodak K., Urbańczyk-Gucwa A., Jabłońska M., Pawlicki J., Mizera J.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 1

331--337

EN

In this study, binary Al–2.3wt%Li alloy, ternary Al–2.2wt%Li–0.1wt%Zr alloy and quaternary Al–2.2wt%Li–0.1wt%Zr–1.2wt%Cu alloy in the solution treated condition and additionally in aging condition were severely plastically deformed by rolling with cyclic movement of rolls (RCMR) method to produce ultrafine grained structure. Scanning transmission electron microscopy (STEM), scanning electron microscopy with EBSD detector (SEM/EBSD) were used for microstructural characterization and hardness test for a preliminary assessment of mechanical properties. The results shows, that the combination of aging treatments with RCMR deformation can effectively increase the hardness of Al–Li alloys. Second particles hinders the annihilation of dislocations in Al matrix during deformation leading to an increase of dislocation density. Significant amount of nanometric second particles in refined structure to ultrafine scale especially in Al–2.2wt%Li–0.1wt%Zr–1.2wt%Cu alloy effectively prevents the formation of high angle boundaries.

16

Niskotemperaturowe starzenie cyrkonowych materiałów ceramicznych Y-tzp. Cz. 2. Wstępne badania procesu z wykorzystaniem techniki EBSD

Tymowicz-Grzyb P., Jaegermann Z.

Szkło i Ceramika

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2017

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R. 68, nr 5

14--18

PL

W publikacji przedstawiono wyniki badania zjawiska starzenia niskotemperaturowego materiałów cyrkonowych metodą opartą na dyfrakcji elektronów wstecznie rozproszonych EBSD (ang. Elektron Backscattered Diffraction). Celem pracy była próba odpowiedzi na pytanie czy metoda EBSD może służyć do zidentyfikowania początkowych etapów procesu niskotemperaturowego starzenia materiałów cyrkonowych Y-TZP. Do celów porównawczych wykorzystano wcześniejsze wyniki badań procesu starzenia prowadzone metodami XRD i obserwacji SEM, opublikowane w części 1 artykułu. Analiza wyników przeprowadzonych badań pokazała, że czułość metody EBSD w wykrywaniu wczesnych zmian transformacji t→m jest znacznie wyższa niż metod XRD i SEM. Analiza obrazów dyfrakcyjnych uzyskanych metodą EBSD wykazała obecność fazy jednoskośnej w powierzchniowych warstwach materiałów pomimo tego, że nie wykazały jej badania dyfrakcyjne XRD.

EN

The results of EBSD (Elektron Backscattered Diffraction) study on the low-temperature degradation (LTD) phenomenon of zirconia materials were presented. The aim of the study was to answer the question whether the EBSD method can be used to identify the initial LTD stages of Y-TZP zirconia. For comparative purposes, previous results on XRD study and SEM observation, published in part 1 of the article, was used. The results of the studies have shown that the sensitivity of EBSD method for detecting early stages of t→m transformation is significantly higher than that of XRD and SEM. Analysis of EBSD diffraction patterns revealed the presence of monoclinic phase in the superficial layers of materials despite the fact that the diffraction patterns did not show it.

17

Zmiany mikrostruktury i własności stopu aluminium 7075 po odkształceniu metodą KOBO i rozciąganiu

Andrzejewski D., Laurentowska-Tyczka A.

Obróbka Plastyczna Metali

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2017

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T. 28, nr 2

93--106

PL

Wysoko wytrzymały i trudnoodkształcalny stop aluminium 7075 w stanie T6 poddano wyciskaniu metodą KOBO w temperaturze 400°C i temperaturze pokojowej. Po wyj- ściu pręta z matrycy zastosowano 2 warianty chłodzenia, tj. w wodzie i na powietrzu. Badano wpływ odkształcenia metodą KOBO (która jest zaliczana do metod SPD) na wielkość ziaren, stosując technikę EBSD, która dodatkowo pozwoliła na określenie kąta dezorientacji pomiędzy ziarnami. Próbki do badań przygotowano techniką polerowania mechanicznego lub elektrochemicznego. Wykazano, że obie metody przygotowania zgładów metalograficznych są odpowiednie, gdyż pozwalają na uzyskanie wyraźnego obrazu dyfrakcji. Niemniej jednak preparatyka jest nieco bardziej złożona niż w przypadku przygotowania zgładów do obserwacji za pomocą mikroskopii świetlnej. Z materiału w stanie wyjściowym oraz z wyciśniętych prętów wykonano próbki wytrzymałościowe, które poddano rozciąganiu w temperaturze pokojowej oraz w 400°C. W przypadku materiału po procesie KOBO wydłużenie wyniosło 247%, co sugeruje uzyskanie stanu nadplastycznego. Pomimo zbliżonego rozmiaru ziarna materiału w stanie wyjściowym nie wykazywał on odkształcenia nadplastycznego, a wydłużenie wyniosło 75%). Wskazuje to na inne czynniki i elementy mikrostruktury niż rozmiar ziarna, które umożliwiają osiągnięcie odkształcenia nadplastycznego. Mikrostruktura po odkształceniu nadplastycznym stopu, pomimo dużego odkształcenia, zawiera ziarna o kształcie w przybliżeniu równoosiowym. Mikrostruktura stopu, po odkształceniu w temperaturze pokojowej, wygląda zupełnie inaczej – ziarna są wydłużone, a pomiędzy nimi znajdują się kolonie w przybliżeniu równoosiowych ziaren.

EN

High-strength and hard-deformable 7075 aluminum alloy in T6 state underwent KOBO extrusion at a temperature of 400°C and room temperature. After the rod’s exit from the die, 2 cooling variants were applied, i.e. in water and in air. The influence of KOBO deformation (classified as an SPD method) on grain size was investigated using the EBSD technique, which additionally made it possible to determine the disorientation angle between grains. Test samples were prepared by the mechanical or electrochemical polishing technique. It was demonstrated that both methods of preparing metallographic specimens are adequate as they afford a clear diffraction picture. Nevertheless, preparation is somewhat more complex than in the case of preparing specimens for light microscopy. Samples for strength testing were made from material in its original state as well as from extruded rods, and these samples underwent tension at room temperature and 400°C. In the case of material after the KOBO process, elongation amounted to 247%, which suggests that a superplastic state was achieved. Despite having similar grain size, the material in its original state did not exhibit superplastic deformation, and elongation equaled 75%. This indicates other factors and microstructural elements other than grain size that enable achievement of superplastic deformation. After superplastic deformation of the alloy, its microstructure still contains grains with an approximately equiaxial shape despite the high deformation. The alloys microstructure after deformation at room temperature has a completely different appearance – grains are elongated, and colonies of approximately equiaxial grains are found between them.

18

Optimization of isothermal transformation period for austempered ductile iron

Parhad P., Likhite A., Bhatt J., Peshwe D.

Metallurgy and Foundry Engineering

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2017

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Vol. 43, no. 4

313--331

EN

The present paper examines and compares the influence of austempering parameters such as temperature and time on the isothermal transformation and microstructural changes of ductile iron. To identify the compositional and structural changes during an isothermal transformation, a very wide austempering period is chosen at a transformation temperature for the precise determination of the process window. XRD, optical, and scanning electron microscopic techniques are exploited to identify and analyze the changes in the austempered structure, at austempering temperatures of 250°C and 400°C. The various structural parameters like austenite volume fraction (Vγ, its carbon content (Cγ), lattice parameter, and the average cell size of the ferrite are ascertained. Electron backscattered diffraction (EBSD) analysis is used to identify the carbide precipitation obtained due to the austempering Stage-II reaction. It is noticed that, at the end of the austempering Stage-II reaction, there is a significant reduction in the volume fraction of stabilized austenite and it’s carbon content, as the microstructure at this stage not only contains ausferrite but also additional precipitated iron carbides. With an increase in austempering time, the austenite and ferrite volume fraction increase until the austenite becomes stabilized with sufficient carbon. The increase in the lattice parameter of the austenite during austempering corresponds to the rise in carbon content within the austenite. A rise in the austempering temperature leads to a reduction in the volume fraction of the ferrite and an increase in the stabilized austenite volume fraction. The optimum isothermal transformation period for austempered ductile iron is established, based on the period during which the maximum content of the austenite volume fraction, its carbon, the lattice parameter, and the average cell size of the ferrite are maintained.

PL

W pracy przedstawiono badania dotyczące wpływu parametrów hartowania izotermicznego takich jak temperatura i czas na izotermiczną transformację i zmiany mikrostrukturalne żeliwa sferoidalnego. W celu określenia zmian strukturalnych i składu chemicznego podczas przemiany izotermalnej został dobrany bardzo szeroki okres hartowania izotermalnego, co pozwoliło na precyzyjne określenie warunków procesu. Zastosowano techniki takie jak dyfrakcja promieniowania rentgenowskiego (XRD), mikroskopia świetlna i skaningowa mikroskopia elektronowa, aby zidentyfikować i przeanalizować zmiany strukturalne po hartowaniu w temperaturach 250°C i 400°C. Określono różne czynniki strukturalne, takie jak udział objętościowy austenitu (Vγ), zawartość węgla w austenicie (Cγ), stała sieciowa oraz średnia wielkość komórki elementarnej ferrytu. Dyfrakcję elektronów wstecznie rozproszonych (EBSD) zastosowano do zidentyfikowania wydzieleń węglików powstałych wskutek reakcji drugiego etapu podczas hartowania izotermalnego. Nie zauważono, aby z końcem reakcji drugiego etapu hartowania izotermalnego nastąpił widoczny spadek udziału objętościowego ustabilizowanego austenitu i zawartości w nim węgla, ponieważ mikrostruktura na tym etapie nie tylko zawiera ausferryt, lecz również wydzielenia węglików żelaza. Wraz z wydłużeniem czasu hartowania udział objętościowy austenitu i ferrytu wzrasta aż do momentu, kiedy austenit zostanie ustabilizowany odpowiednią ilością węgla. Zwiększenie stałych sieciowych austenitu w trakcie hartowania izotermalnego prowadzi do zmniejszenia udziału objętościowego żelaza i wzrostu udziału ustabilizowanego austenitu. Optymalny okres transformacji izotermalnej hartowanego żelaza sferoidalnego został określony na podstawie okresu, podczas którego maksymalna zawartość udziału objętościowego austenitu, zawartego w nim węgla, stałej sieciowej i średniej wielkości komórki elementarnej ferrytu była utrzymana.

19

Phase transformation and deformation behavior of steels with different content of metastable austenite

Klein M. W., Skorupski R., Smaga M., Beck T.

Engineering Transactions

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2017

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Vol. 65, iss. 1

69--75

EN

In this investigation three steels HCT 780T, AISI 347 and HSDr 600 with different content of metastable austenite and different austenite stability were monotonically loaded at ambient temperature. Using x-ray diffraction and scanning electron microscopy changes in the microstructure were characterized in detail. Hence, the most important mechanisms, which occur by deformation were determined.

20

Thermal Stability of AA1050 Aluminum Alloy after Equal Channel Angular Pressing

Koprowski P., Bogucki R., Bieda M., Kawałko J., Sztwiertnia K.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2A

777--786

EN

The annealing behavior of AA1050 aluminum alloy deformed by equal-channel angular pressing (ECAP) was studied experimentally. The material was subjected to extrusion through die with channels intersecting at an 90° angle. Samples were pressed for up to 8 passes using route BC, then cut into slices and subsequently annealed for 1 hour at temperatures from 100°C to 350°C. Hardness measurements were performed on each slice. Microstructure of material was analyzed in the longitudinal section by means of Electron Backscatter Diffraction system in a scanning electron microscope (EBSD/SEM). From the obtained sets of Kikuchi diffraction patterns orientation maps and Image Quality maps were determined. Grain size, disorientation distributions and crystallographic texture were also estimated. ECAP caused significant improvement of hardness, with stabilization after 4 passes. Refinement of microstructure was obtained with the increasing amount of passes. Material properties were stable during annealing at temperatures lower than 150°C. Annealing at higher temperatures caused a decrease in hardness corresponding to an increase of the grain size.