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1

Study of phase transformations in complex phase steel using a mesoscale cellular automaton model part 2: Experiments and validation

Opara Jarosław, Kuziak Roman

Journal of Metallic Materials

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2020

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Vol. 72, no. 3

32--44

EN

A two-dimensional mesoscale model based on the concept of hybrid cellular automata was used to study phase transformations in a complex phase steel during continuous cooling. This model enables simulation of the decomposition of austenite into ferrite, bainite, and martensite, accompanied by calculations of volume and grain boundary diffusion of carbon. In effect, as a result, one can observe the morphology of simulated microstructures, corresponding carbon segregation as well as microhardness distribution. These results with the kinetics of austenite to ferrite phase transformation and predicted values of the complex phase steel hardness are the subject of model validation. A series of dilatometric experiments were carried out with constant cooling rates in order to construct a CCT diagram and validate the presented model. The convergence of simulated results with empirical outcomes was confirmed quantitatively using a dedicated goal function and data summaries in the table and graphs. However, some qualitative and quantitative discrepancies in terms of microstructure morphology are indicated which was possible thanks to applying a wide range of different validation parameters of the model. It is emphasized how crucial is the use of appropriate validation methodology.

PL

Dwuwymiarowy mezoskalowy model oparty na koncepcji hybrydowych automatów komórkowych zastosowano do badania przemian fazowych w stali wielofazowej podczas ciągłego chłodzenia. Model ten umożliwia symulację rozpadu austenitu w ferryt, bainit i martenzyt wraz z obliczeniami objętościowej i granicznej dyfuzji węgla. W efekcie można zaobserwować morfologię symulowanych mikrostruktur, odpowiadającą im segregację węgla, a także rozkład mikrotwardości. Wyniki te wraz z kinetyką ferrytycznej przemiany fazowej i przewidywanymi wartościami twardości stali wielofazowej są przedmiotem walidacji modelu. Przeprowadzono szereg eksperymentów dylatometrycznych przy stałych szybkościach chłodzenia w celu opracowania wykresu CTPc i walidacji przedstawionego modelu. Zbieżność wyników symulacji z danymi empirycznymi została potwierdzona ilościowo za pomocą dedykowanej funkcji celu oraz zestawienia danych w tabeli i na wykresach. Jednakże, wskazano na pewne rozbieżności jakościowe i ilościowe pod względem morfologii mikrostruktury, co było możliwe dzięki zastosowaniu szerokiego wachlarza różnych parametrów do walidacji modelu. Podkreślono, jak istotne jest zastosowanie odpowiedniej metodologii walidacji.

2

Effects of multi-pass FSP on the β phase (Mg17Al12) distribution and mechanical properties of AZ91C magnesium alloy

Rouhi S., Dadashpour M., Mostafapour A., Doniavi A.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 82, nr 2

77--85

EN

Purpose: The principle and advantages of friction stir processing (FSP) for the production of a highly formable Mg alloy, and some convincing experimental results are reported in this paper. The aim is to understand the relationship between the microstructure characteristics and the mechanical properties behaviour of the number of FSP passes AZ91C alloy. Design/methodology/approach: FSP is a solid state processing technique which involves plunging and traversing a square pin profiles FSP tool through the material. In this study, a fine-grained multi-phase AZ91C magnesium alloy was produced by applying FSP on as-cast AZ91C alloy. Findings: FSP achieved grain refinement and homogenization of the as-cast microstructure in Mg alloy AZ91C. FSP produced a fine homogeneous microstructure having a grain size of 6 μm throughout the plate. Also tensile properties of the specimen produced in one, two and three passes were investigated by standard tensile test. Results show that FSP improved the tensile characteristics of the as cast AZ91C alloy significantly. As the number of passes increased, higher UTS and TE were achieved due to finer grains and more dissolution of β phase (Mg17Al12). Originality/value: The present study shows that FSP is an efficient production method for a large-scale plate of a highly formable Mg alloy.

3

Microstructure characterization of localized corrosion wear of Cr/Cr2N+ a-C:H/a-C:H:Cr multilayer coatings on carbon fiber composites

Janusz M., Major L., Lackner J. M., Grysakowski B., Krawiec H.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 2

171--177

EN

The use of carbon fiber composites (CFC) for different applications is widespread. Carbon-based materials show, however, significant oxidative degradation in air. Modern materials are subjected to aggressive, corrosive environment. This type of environment may strongly reduce their mechanical properties. For the protection of CFC, it was necessary to apply coatings to the composite surface. In the presented paper, a chromium/chromium nitride (Cr/Cr2N) multilayer structure has been selected as the inner part. The outer part of the coating was a hydrogenated amorphous carbon (a-C:H), gradually implanted by Cr nanocrystals. The application of transmission electron microscopy (TEM) indicated that the proposed deposition method allowed the formation of a Cr/Cr2N multilayer of Λ = 150 nm, topped with a-C:H+ Cr23C6 composite of a varied carbides density. The micro-hardness of the deposited coatings was up to 14 GPa (at a load of 2 and 5 mN). The microstructure of the deposited coatings was described in detail by means of TEM in the authors’ recently published paper [1]. This paper is a continuation thereof, aimed at describing microstructure changes after a localized corrosion process. In order to study localized corrosion in coatings, particularly in metallic (Cr) interlayers, the potential measurements and voltammetry experiments were performed in a Ringer solution. The open-circuit potential reaches stable values after a sufficient time period. The results indicated that the presence of a-C:H+Cr23C6, the outer part of the coating, speeds up the localized corrosion process in Cr interlayers in the inner part of a coating.

4

Characterization of thermally oxidized titanium based coating

Cetiner D., Paksoy A. H., Tazegul O., Atar E., Cimenoglu H.

Journal of Achievements in Materials and Manufacturing Engineering

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2016

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Vol. 75, nr 2

49--54

EN

Purpose: Aim of the study is to improve the bioactivity of CoCr alloy upon covering the surface with titanium based coating. Design/methodology/approach: CoCr alloy was coated by cold spraying of powder mixture having a composition of 92 wt.%Ti + 8 wt.%Al. Coated samples were thermally oxidized at 600°C for 60 hours. Characterization of the coating was made by X-Ray diffraction analyses, microstructural surveys, cross-section and surface SEM elemental mapping analyses, roughness and hardness measurements. Findings: Results showed that sequential application of cold spray and thermal oxidation processes provided the multi-layered coating consisting of an inner titanium based layer and an outer oxide layer consisted of TiO2 and Al2O3. Thermal oxidation also caused the remarkable increasing in the surface hardness as compared to the as-cold sprayed state. Practical implications: Modifying the surface of CoCr metallic implants for long term success. Originality/value: Producing a multilayer coating on the surface of the CoCr alloy for biomedical application by sequential application of cold spray and thermal oxidation processes is the orginality of the study.

5

A comparative study of Ti-Al and Ti-Nb alloys for advanced technological applications

Peter I., Rosso M., Castella C.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 73, nr 2

199--205

EN

Purpose: of this paper is to compare some properties of Ti-Al and Ti-Nb alloys to investigate on the possibility to jointly employed them industrially. Ti-Al alloys have been proposed because they present challenging characteristics for high temperature purposes and β type Ti-Nb alloy has specific mechanical properties at room temperature. Ti-Al alloys are very attractive materials and represent one of the most important materials employed for aero jet engines. The most promising alloy belonging to the above mentioned classes are predominantly based on simultaneously presence of two phases, namely γ-TiAl (gamma titanium aluminides) and α2-Ti3Al both with a fully lamellar microstructure and could replace Ni-based superalloys in some high temperature applications in aerospace and automotive industries. The most important advantages of such alloys compared to some superalloys consist in their low density correlated to their superior efficiency in service and reduced gas emission. Design/methodology/approach: The Ti-Al alloy have been produced by gravity casting, using a vibrating furnace, while the Ti-Nb alloy samples have been realized by the cold crucible levitation melting (CCLM) casting technology. Microstructural and mechanical characterization have been performed. Findings: The microstructural analysis for the Ti-Al alloy reveals a fully-lamellar microstructure with alternate plates of α2-(Ti3Al) and γ-(TiAl) plates. The grains have an average size of about 200 μm. For the Ti-Nb based alloy only a β mono-phase has been detected. This alloy has a equiaxed microstructure with an average grain dimension of about 170 μm. The Ti-Nb alloy presents a high mechanical strength while on the contrary that of the Ti-Al has been deleteriously affected by the presence of large gas porosities. Superior hardness values have been reached with Ti-Al alloy, due to the presence of hard γ-TiAl. Practical implications: The most important implication is related to the transfer toward the proper choice of the correct parameters during manufacturing. Originality/value: Investigation on the influence of the elemental composition enriched by other elements and casting processes on the defect development, the microstructural characteristics and on the mechanical behaviour of the alloys.

6

Microstructural characterization of gas phase aluminized TiAlCrNb intermetallic alloy

Moskal G., Góral M., Swadźba L., Mendala B., Hetmańczyk M., Witala B.

Archives of Metallurgy and Materials

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2012

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Vol. 57, iss. 1

253-259

EN

This article presents a microstructure characterization of an alloy coating based on Ti-48Al-2Cr-2Nb- type γ + α2 intermetallic phases deposited via an out-of-pack aluminizing process. The goal of the aluminizing process was to obtain a coating composed of aluminum-rich TiAl2 or TiAl3 phases with greater oxidation resistance compared to the base alloy. The results showed that the gas-phase aluminizing process produced a coating with specific microstructural properties. The thickness of the layer obtained, including the transition zone, was approximately 20µm. X-ray diffraction (XRD) phase composition studies demonstrated that the outer coating zone was primarily composed of a TiAl2 phase, and its thickness was approximately 10 µm. Microanalysis of the chemical composition showed that, in addition to the main components, i.e. titanium and aluminum, chromium and niobium were present in the outer coating. Electron backscatter diffraction (EBSD) studies further indicated the probable presence of a TiAl2 phase. The coating obtained was of good quality, and cracks or pores, which are typical of coatings obtained via powder methods, were not detected.

PL

W artykule przedstawiono wyniki badań mikrostruktury warstwy wierzchniej stopu na osnowie faz międzymetalicznych γ + α2 typu Ti-48Al-2Cr-2Nb po procesie aluminiowania metodą out-of-pack. Celem procesu aluminiowania było uzyskanie warstwy zewnętrznej zbudowanej z bogatych w aluminium faz typu TiAi2 lub TiAl3 o wyższej odporności na utlenianie w porównaniu do stopu podłoża. Zrealizowane badania wykazały, że zastosowanie metody aluminiowania gazowego pozwoliło na wytworzenie na powierzchni stopu pokrycia o zakładanych właściwościach mikrostrukturalnych. Grubość otrzymanej warstwy, łącznie ze strefą przejściową wynosiła ok. 20 µm. Mikroanaliza składu chemicznego wykazała również, że poza głónymi składnikami tj. tytanem i aluminium w obszarze tym obecne były również chrom i niob. Badania EBSD wykazały ponadto prawdopodobną obecność fazy Ti3Al5. Uzyskane pokrycie było dobrej jakości, nie stwierdzono pęknięć ani pustek, typowych dla warstw otrzymanych metodami proszkowymi.

7

Analiza zmian mikrostruktury i właściwości lutowi stosowanych w witrażach w okresie od XIII do XX wieku

Garbacz H., Pura J., Zwolińska M., Hensel Z., Kurzydłowski K. J.

Inżynieria Materiałowa

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2011

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Vol. 32, nr 3

168-175

PL

Przedmiotem badań były 22 fragmenty lutowi pochodzących z witraży wykonanych w okresie od XIII do XX wieku w obiektach sakralnych z terenu Wielkiej Brytanii, Hiszpanii, Belgii, Niderlandów i Polski. Celem przeprowadzonych badań było określenie cech wspólnych lutowi w zakresie składu chemicznego użytych materiałów oraz zastosowanych technologii, a także wskazanie parametrów, które pozwolą na identyfikację złączy witraży z nieznanego miejsca lub okresu pochodzenia. W ramach pracy dokonano analizy źródeł literaturowych na temat wydobycia i metalurgii ołowiu w Europie od XIII wieku. Badane próbki charakteryzowano na podstawie analizy makroskopowej, obserwacji mikroskopowych oraz pomiarów mikrotwardości. Wykonano także szczegółowe badania składu chemicznego za pomocą mikroanalizy rentgenowskiej (EDS), spektroskopii promieniowania rentgenowskiego (XRF) oraz spektroskopii elektronów Auger (AES). Ponadto przeprowadzono analizę składu fazowego metodą dyfrakcji promieniowania rentgenowskiego. Badania makroskopowe wykazały charakterystyczne cechy topograficzne oraz barwy powierzchniowych nalotów. Na powierzchniach bocznych niektórych próbek ujawniono odciski będące śladami po procesie walcowania wzdłużnego. Zauważono także charakterystyczne cechy stanu powierzchni lutowi w zależności od miejsca ich pochodzenia. Na podstawie analizy składu chemicznego ujawniono podobieństwa oraz cechy charakterystyczne próbek pochodzących z poszczególnych obszarów Europy.

EN

Object of the studies were 22 pieces of solder from the stained-glass windows. Samples were collected from historical places from the Great Britain, Spain, Belgium, the Netherlands and the Poland in the period of XIIIth to XXth century. On the basis of data from literature the history of mining and metallurgy of lead in Europe were described. The aim of the study was to determine the common characteristics of the samples, including similarities in the chemical composition of the materials and technology used. Far-reaching aim was to determine the parameters that will allow the identification of stained-glass joints with an unknown place or period of origin. The samples were characterized using macroscopic and microscopic observations. The mechanical properties of the solders were analyzed by microhardness tests. The investigations of the chemical composition using energy-dispersive X-ray microanalysis (EDS), X-ray spectroscopy (XRF), Auger electron spectroscopy (AES) and phase analysis by X-ray diffraction were performed. In the macroscopic analysis the geometry and deposits on the surface of the samples were described. It has been found that the shape of the samples depends on the technology which was used for solder production. Characteristic relief on the samples after rolling process was observed. The colour and type of the deposits are connected with place of the solder origin. In the case of EDS analysis the relationship between chemical composition and the period of solder creation was observed.

8

Charakterystyka mikrostruktury powłokowych warstw barierowych typu RE2Zr2O7

Moskal G.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 4

1113-1116

PL

W artykule przedstawiono wyniki oceny mikrostruktury powłokowych warstw barierowych otrzymywanych w wyniku natryskiwania plazmowego proszków o ogólnym wzorze RE2Zr2O7. Zastosowano standardowe parametry procesu natryskiwania metodą APS. Dokonano oceny wizualnej warstw oraz ilościowej i jakościowej charakterystyki zewnętrznej warstwy ceramicznej metodą mikroskopii laserowej. Określono chropowatość oraz inne parametry geometryczne opisujące powierzchnię warstw TBC. Dokonano również oceny składu chemicznego i fazowego warstwy ceramicznej oraz oceny mikrostruktury warstw z punktu widzenia spełnienia warunków kryterialnych oceny powłokowych warstw ceramicznych. Wykonano także badania porowatości międzywarstwy oraz warstwy ceramicznej. Oceniono także ogólną jakość układu TBC z punktu widzenia obecności pęknięć, rozwarstwień oraz porowatości masywnej. Stwierdzono, że otrzymane warstwy nowego typu spełniają wymagania jakościowe stosowane do oceny warstw konwencjonalnych otrzymywanych w wyniku natryskiwania tlenku 8YSZ.

EN

The paper presents microstructural assessment results of thermal barrier coatings deposited by plasma spraying of the powders with the general formula of RE2Zr2O7. Standard parameters of the air plasma spraying (APS) method were used. A visual assessment of layers and quantitative and qualitative characteristics of an outer ceramic layer with the laser microscopy method were performed. Roughness and other geometric parameters describing the TBC surface were determined. Chemical and phase composition analysis of the ceramic layer was also carried out. Microstructural assessment of the layers for meeting the assessment criteria of the ceramic coatings was also carried out. The interlayer and ceramic layer porosity assessment was performed. The TBC system general quality was assessed for presence of cracks, delamination and massive porosity. It was found that the new type of layers obtained meet the quality requirements used for assessment of the conventional layers obtained by spraying 8YSZ zirconia.

9

Charakterystyka mikrostruktury i odporności na utlenianie pokryć aluminidkowych o różnej zawartości krzemu uzyskane na stopie TiAlCrNb metodą zawiesinową

Moskal G., Swadźba L., Góral M., Supernak W.

Inżynieria Materiałowa

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2006

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Vol. 27, nr 5

1136-1139

PL

W artykule przedstawiono wyniki badań związane z kształtowaniem struktury i właściwości warstwy wierzchniej stopu międzymetalicznego Ti-48Al-2Cr-2Nb poprzez wytworzenie, metodą Arc-PVD, pokrycia żaroodpornego typu TiAlSi. Zaproponowano rozwiązanie, polegające na zastosowaniu metody Arc-PVD i przy jej pomocy wytworzeniu na powierzchni stopu pokrycia zbudowanego z fazy Ti(Al,Si)3 oraz faz krzemkowych Ti-Si. Otrzymane pokrycie charakteryzowała się grubością rzędu 30-40 um i zbudowana byłą z dwóch podwarstw. Warstwę zewnętrzną, o grubości ok. 35 um, tworzyła zawierająca krzem faza TiAl3. Drugą strefę stanowiła warstwa przejściowa o grubości ok. 5 (am, utworzona z ziarn słupkowych faz TiAl2 oraz fazy Ti(Al,Si)3. Przeprowadzono także próby odporności na utlenianie izotermiczne krótkotrwałe (950°C/200 godzin), cykliczne krótkotrwałe (950°C/2400 cykli - 200 godzin) i cykliczne długotrwałe (950°C/60 cykli -1380 godzin). Stop podłoża charakteryzuje się niezadowalającą odporność na utlenianie izotermiczne oraz cykliczne, co wynika z wytworzenia zgorzeliny złożonej z mieszaniny tlenków AI2O3 i Ti02. Żaroodporność próbek z pokryciem jest wyższa niż w przypadku stopu podstawowego. Powstała zgorzelina ma mniejszą grubością, a dominującym jej składnikiem jest pożądany tlenek A1203. Korzystny wpływ zastosowanego pokrycia, na poprawę żaroodporności stopu podstawowego, wynika z obecności bogatej w aluminium oraz krzem fazy TiAk oraz krzemków tytanu typu TisSi3 również o wysokiej żaroodporności i dodatkowo zmniejszającej skłonność do utleniania tytanu.

EN

In this article results of microstructural investigations and oxidation resistant of aluminide coating modified by Si was presented. Protective TiAISi type coating were deposited by Arc-PVD method. This type of protective coating contained two sublayers. Outside layer had a thickness 35um and contained TiAl3 phase modified by Si as main component. The second layer was found as transition area between TiAb outside layer and surface of TiAlCrNb substrate. The thickness of inside sublayer was 5um. This area was build from "fingerlike" grains of TiAl2 phase and TiAl3 rich in Si. Results of the long- and short-time cyclic and isothermal oxidation tests of based intermetallic Ti-48-2-2 alloy with and without oxidation resistance coating modified by Si was showed as well. Isothermal oxidation were carried out at 950°C by 200 hours in laboratory air. Short-time cyclic oxidation tests were carried out at 950°C too. The heating and cooling time was 5 minutes (3°C/s). The total of 2400 cycles were performed. Long-term cyclic oxidation tests were carried out at 950°C as well. Heating time was 23 hours and cooling was made in static air. The total of 60 cycles were performed (1380h). It is seen from results of three types of oxidation tests that Ti-Al-Si coatings improve the oxidation resistance of TiAl alloy in all conditions of performed tests. The effect of this type diffusion coatings to improve oxidation behaviour was attributed to the surface layer consisting of TiAl3. Concerning the structure of the modified aluminide layer, the effect of silicon addition is the generation a new Ti-Si intermetallic phases and subsequently aluminium rich zone on the surface of substrate alloy.