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1

Application of Artificial Neural Network for Prediction of the Cyclic Oxidation Behavior of Electrical Resistance Sintered Gamma-TiAl Intermetallics

Garip Yiğit, Garip Zeynep Batık, Ozdemir O.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

581--591

EN

TiAl based intermetallics are widely used for structural applications in aviation, chemical engineering, automotive and sports equipment. In this study, the electrical resistance sintering (ERS) technology used in the production of gamma-TiAl intermetallics is based on the principle of applying pressure simultaneously with a high-density electric current. The purpose of this study was to investigate the cyclic oxidation resistance of Ti-44Al-3Mo and Ti-44Al-3Nb alloys (at.%) and the applicability of artificial neural network (ANN) modeling for the forecast of the oxidation behavior of these alloys. In order to obtain this aim, the alloys sintered by ERS were oxidized at 900°C for 360 h and then the oxidation behaviors of them are evaluated by plotting a graph between weight change as a function of time. The data collected after the oxidation experiments were used to construct the prediction models. The modelling results show that a good agreement between experimental results and prediction results was found. The oxidized alloys were characterized using XRD and SEM-EDS. The XRD patterns revealed the oxidation products are composed of TiO2 and Al2O3 oxides. SEM-EDS analysis indicated that the oxide scales of alloys are made up of a multilayered structure.

2

Effect of Wetting Agent and Carbide Volume Fraction on the Wear Response of Aluminum Matrix Composites Reinforced by WC Nanoparticles and Aluminide Particles

Lekatou A., Gkikas N., Karantzalis A. E., Kaptay G., Gacsi Z., Baumli P., Simon A.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1235--1242

EN

Aluminum matrix composites were prepared by adding submicron sized WC particles into a melt of Al 1050 under mechanical stirring, with the scope to determine: (a) the most appropriate salt flux amongst KBF4 , K2 TiF6 , K3 AlF6 and Na3 AlF6 for optimum particle wetting and distribution and (b) the maximum carbide volume fraction (CVF) for optimum response to sliding wear. The nature of the wetting agent notably affected particle incorporation, with K2 TiF6 providing the greatest particle insertion. A uniform aluminide (in-situ) and WC (ex-situ) particle distribution was attained. Two different sliding wear mechanisms were identified for low CVFs (≤1.5%), and high CVFs (2.0%), depending on the extent of particle agglomeration.

3

Właściwości mechaniczne warstw kompozytowych na bazie faz międzymetalicznych NixAly, CrxAly i TixAly wytworzonych na jednofazowym stopie tytanu alfa

Ossowski M., Spychalski M., Wierzchoń T.

Inżynieria Materiałowa

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2012

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Vol. 33, nr 3

197--201

PL

Fazy międzymetaliczne na bazie aluminium są interesującym materiałem ze względu na ich małą gęstość, dużą wytrzymałość oraz żaroodporność wynikającą ze zdolności do tworzenia się na ich powierzchni ochronnej zgorzeliny tlenku aluminium Al2O3. Właściwości ochronne takiej zgorzeliny zależą głównie od jej jednorodności fazowej, co gwarantują jedynie fazy międzymetaliczne o dużej zawartości aluminium. Zastosowanie takich faz międzymetalicznych jako materiałów konstrukcyjnych jest niemożliwe lub w dużym stopniu ograniczone ze względu na ich skłonność do kruchego pękania oraz niską plastyczność. Perspektywicznym kierunkiem wykorzystania ochronnych właściwości faz międzymetalicznych na bazie aluminium jest ich wytwarzanie technikami inżynierii powierzchni w postaci warstwy wierzchniej na materiałach i elementach przeznaczonych do pracy w podwyższonej temperaturze. W artykule przedstawiono wyniki badań mikrostruktury oraz właściwości mechanicznych warstw kompozytowych na bazie faz międzymetalicznych typu Ni xAly, CrxAly i Ti xAly wytworzonych na technicznym stopie tytanu. Badane warstwy otrzymano metodą hybrydową, łączącą wytwarzanie bimetalicznych powłok niklu, chromu i aluminium z obróbką w warunkach wyładowania jarzeniowego. Tak wytworzone warstwy charakteryzują się większą niż stop tytanu twardością, powyżej 900 HV0,1, mają charakter dyfuzyjny, zapewniający bardzo dobrą przyczepność do podłoża, jak również zwiększają odporność na zużycie przez tarcie obrabianego stopu. Ponadto opracowana metoda pozwala na wytworzenie tych warstw w temperaturze poniżej przemian fazowych dla większości stopów tytanu.

EN

Aluminium base intermetallic phases with their unique properties like low density, high mechanical strength, high melting temperature and resistance to oxidation at high temperature, are being extensively investigated at present. The mechanism of high temperature oxidation protection is based on the formation of a thermally-stable Al2O3 scale on their surfaces, which eliminates or at least reduces the diffusion of oxygen. Intermetallic phases with a high aluminium content which form a pure single phase alumina layer show the best protective performance. The factors limiting wider use of high aluminium intermetallics as constructional materials are chiefly related to their poor plasticity and liability to brittle fracture. The prospective direction of further investigation to take advantage of the unique properties of aluminium base intermetallics as surface layers produced on constructional, high temperature materials. The paper presents the investigation of the microstructure and mechanical properties of intermetallic Ni xAly, CrxAly and TixAly base surface layers produced on titanium Grade 2. The layers were produced by the hybrid method that combines the processes of producing bimetallic Ni, Cr and Al coatings by magnetron sputtering with a glow discharge treatment. The produced composite layers have a higher than titanium alloy hardness up to 900 HV0,1, a diffusion character which gives them great adhesion to the surface and high friction wear resistance. Moreover, the developed hybrid method allows one to produce these layers at temperature below the betatransus temperature for the majority of titanium alloys.

4

Effect of solidification conditions on microstructure of Ni3Al/C composite

Janas A., Olejnik E., Kolbus A., Kmita A.

Kompozyty

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2011

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R. 11, nr 3

220-224

EN

The influence of the solidification conditions on the microstructure of an Ni3Al/C composite, i.e. an engineering material in which the role of a lubricating phase, usually performed by reinforcing phases, is played by carbon, has been studied. When proper conditions are observed, a nickel-aluminium alloy composed in 87 wt. % of nickel and in 13 wt. % of aluminium, containing moreover carbon in an amount of 2.5 wt. %, forms in the solidification process a natural Ni3Al/C "in situ" composite. The composite matrix is nickel aluminide characterised by very interesting functional properties, particularly high strength at elevated temperatures. An inspiration to these studies was the surprisingly similar microstructure observed in different types of cast iron and in the fundamentally different, in regard to chemical composition, structure and microstructure, nickel - aluminium alloy. The aim of the present study was to evaluate the effect of the solidification conditions on the shape of the precipitates of graphite particles. The morphologies of the graphite phases were examined and their chemical composition was determined.

PL

W pracy przedstawiono wpływ warunków krystalizacji na mikrostrukturę kompozytu Ni3Al/C. W materiale tym osnowę stanowi aluminid niklu Ni3Al wykazujący atrakcyjne właściwości wytrzymałościowe w wysokich temperaturach, a fazą smarującą jest grafit. Do wytworzenia osnowy kompozytu wykorzystano nikiel i aluminium o udziale atomowym odpowiadającym stechiometrii fazy Ni3Al. Wytopy prowadzono w piecu próżniowym w atmosferze argonu. Fazę smarującą otrzymano wprowadzając do ciekłego stopu 2.5% wagowych grafitu. W celu zapewnienia różnych warunków krystalizacji przygotowane stopy odlewano do różnych form, tj. molochitowej, kokili chłodzonej na powietrzu, kokili chłodzonej ciekłym azotem. Jeden ze stopów pozostawiono w tyglu w celu uzyskania bardzo wolnej krystalizacji. Proces krzepnięcia stopów rejestrowano, wykorzystując standardową analizę termiczną. Przeprowadzone badania metalograficzne wykazały obecność w mikrostrukturze wydzieleń grafitu płatkowego i sferoidalnego oraz ich kombinacji. W przypadku dużych prędkości krystalizacji 25 i 100 K/s obserwowano w mikrostrukturze przewagę grafitu kulkowego. Mała prędkość chłodzenia 1 i 5 K/s sprzyjała krystalizacji grafitu płatkowego. Zaobserwowano również występowanie typowej eutektyki grafitowej przy prędkości 15 K/s.

5

Synthesis and evaluation of the structure of Ni3Al/C alloy

Kmita A., Janas A., Hutera B.

Metallurgy and Foundry Engineering

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2009

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Vol. 35, no. 2

147-154

EN

The article specifies a method used for the manufacture of a new Ni-Al-C alloy with the description of alloy microstructure. When proper conditions are maintained, the said alloy after solidification forms a natural "in situ" Ni3Al/C composite. Particular attention was paid to the process of synthesis of Ni3Al phase by the technique of cost-effective melting and to the process of the formation of different graphite forms after the solidification in ceramic mould of casting characterised by different wall cross-sections, and hence by different heat transfer rates. Metallographic examinations were carried out by the commonly used techniques and by scanning electron microscopy. The use of the latter enabled the determination of the chemical composition of phases formed during casting process. The aim of the present studies was to evaluate the microstructure of this unique alloy. The phase morphologies were examined and their chemical composition was determined. These fundamental studies should enable the determination of conditions under which the graphite eutectic is formed in Ni-Al alloy and, as a consequence, the synthesis of Ni3Al/C composite.

PL

W prezentowanym artykule przedstawiono metodę otrzymywania nowego stopu Ni-Al-C oraz opisano jego mikrostrukturę. Przy zachowaniu odpowiednich warunków stop ten, po procesie krystalizacji, tworzy naturalny kompozyt ,,in situ" Ni3Al/C. Zwrócono szczególną uwagę na proces syntezy fazy Ni3Al metodą OPW (oszczędnościowego procesu wytopu) i tworzenia się różnych form grafitu po procesie krystalizacji w formie ceramicznej, przy różnych grubościach odlewu, co za tym idzie, przy różnych prędkościach odprowadzenia ciepła. Do badań metaloznawczych wykorzystano tradycyjne metody metalograficzne oraz badania z wykorzystaniem mikroskopu skaningowego. Zastosowanie tego ostatniego umożliwiło określenie składu chemicznego faz, wytworzonych w procesie odlewniczym. Celem podjętych badań było dokonanie oceny mikrostruktury tego nietypowego stopu. Zbadano morfologię występujących faz i określono ich skład chemiczny. Te badania o charakterze podstawowym, pozwolą określić warunki powstawania eutektyki grafitowej w stopie Ni-Al, co w konsekwencji umożliwi syntezę kompozytu Ni3Al/C.

6

Influence of heat treatment on microstructure of slurry aluminide coatings type TiAlSi obtained on TiAlCrNb alloy

Moskal G., Witala B., Rozmysłowska A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 2

204-210

EN

Purpose: Influence of heat treatment on microstructural changes in slurry TiAlSi coating deposited with 12.5% Si concentration on Ti48Al2Cr2Nb intermetallic alloy and investigation of the influence of Si addition on the structure of obtained coatings is a purpose of this paper. Design/methodology/approach: The research allowed identifying microstructural changes that took place during annealing at 950°C of the TiAlSi coating for 2 to 10h exposure in air. A scope of the research encompassed a microstructural analysis with the use of macro and micro investigation - LM, SEM microscopy, XRD phase analysis and EDS analysis. Findings: The investigation has shown that the thickness of the TiAlSi coatings in initial conditions and after a test was in a range from 30 to 40 ěm. The structure of the silicon-modified aluminide coatings is as following: the outer zone consisting of the TiAl3 phase and titanium silicides / the middle zone consisting of columnar titanium silicides in phase TiAl3 matrix / the inner zone consisting of TiAl2 phase. Basic changes were related to differences in thickness in sublayers. Research limitations/implications: The discussed research proves that main reason of much better protection of TiAlSi coated base alloy is related to high microstructure stability of Si modified in TiAl3 phases. In addition silicon decreases activity of titanium, and in consequence the susceptibility of Al to selective oxidation is much stronger. The presence of Si due to Ti-Si phase generation with high oxidation resistance is presented. Practical implications: The slurry method can be applied in aerospace and automotive industry as low-cost technology in production of aluminide coatings on intermetallics. Originality/value: New method of aluminide coatings deposition on TiAl alloys.

7

Kompozyt warstwowy Al z fazami z układu Ti-Al otrzymany w wyniku wygrzewania izotermicznego

Olszówka-Myalska A.

Rudy i Metale Nieżelazne

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2008

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R. 53, nr 4

216-220

PL

Przedstawiono możliwość uzyskania kompozytu warstwowego Al-fazy z układu Ti-Al w wyniku wygrzewania izotermicznego pakietów folii aluminiowej z proszkiem tytanu. Scharakteryzowano makrostrukturę i przedstawiono model zmian mikrostruktury układu warstwowego dla zastosowanych warunków konsolidacji komponentów. Stwierdzono zgodność zmian strukturalnych proszku tytanu w intermetalik z modelem dyfuzyjnego wzrostu warstwy na granicy Al-Ti.

EN

The possibility of obtaining of layered composite from aluminium foil and titanium powder by conventional isothermal heating was analyzed. The interaction between aluminium and titanium was characterized by differential thermal analyze DTA (fig. 1). The exothermal effects were stated as a result of a new phase formation. The composite samples were fordem at the temperature range of 630-680 degrees of Celsius and time range of 5-20 min. The macrostructure strongly depended on the parameters used during the processing (tab. 1, fig. 2, 3). In the layered composite aluminium - (aluminium with a particles containing Ti) - aluminium the intermetallic from the Al-Ti system was formed on the interface Al matrix-Ti particle (fig. 4, 5). The scheme of structure transformation of Al foil-Ti powder-Al foil packs during annealing under pressure was presented (fig. 6). The hardness of each layer of composite was measured (Al 38 HV0,2, Al with particles 95-180 HV0,2). There was stated that only diffusional processes can be used to the components consolidation in the proposal conditions. Using the self-propagating-synthesis (SHS) for the intermetallic formation, because of intensive energy emission, seems to be dangerous in conventional heat treatment furnace.

8

High temperature corrosion of TiAlCrNb alloy with TiAl2 out-of-pack coating in N2-O2-SO2-HCl environments

Moskal G., Sozańska M., Góral M.

Advances in Materials Science

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2008

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Vol. 8, nr 1(15)

121-128

EN

In this article results of microstructural analysis and corrosion resistance tests of 48-2-2 alloy (TiAlCrNb) with and without protective coating were presented. The aluminide coating was deposited by out-of-pack method on the base alloy. The thickness of the coating was 10[mi]m and it was composed of TiAl2 phases. The corrosion resistance tests of the base alloy with and without the protective coating have been conducted at 600°C in the at-mosphere containing nitrogen, with the addition of 9% of O2, 0,08% of S02 and 0,20% of HCl. The tests lasted for 1250h. The aim of the conducted tests was to determine the mass gain of the samples in the given conditions and to identify the corrosion products, using X-ray phase analysis and EDS chemical content microanalysis. The detailed investigation has been done after 25,50, 100, 150, 250, 500,750, 1000 and 1250h of testing. As clearly indicated by the results of investigations, aluminide coating improves the corrosion resistance of TiAl alloy in the conditions of the performed test. The corrosion-resistance-enhancing effect of this type of diffusion coatings was attributed to the surface layer consisting of TiAl2.

9

Microstructure and oxidation behaviour of TiAlSi coatings on TiAlCrNb alloy

Moskal G.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

263-266

EN

Purpose: Influence of slurry coating deposition TiAlSi with different Si concentration on oxidation resistance of Ti48Al2Cr2Nb intermetallic alloy and investigation of the influence of Si addition on the structure of obtained coatings. Design/methodology/approach: The research allowed the identification of microstructural changes that take place during oxidation test of TiAlSi coating during isothermal oxidation at 900 degrees centigrade for 500 h of exposure in air. The scope of the research encompassed a microstructural analysis with the use of macro and micro investigation - LM, SEM microscopy, XRD phases analysis and EDS analysis. Findings: The investigation has shown that the thickness of the coatings TiAlSi was in range from 30 to 40 mm. The structure of the silicon-modified aluminide coatings is as follows: the outer zone consisting of TiAl3 phase and titanium silicides/the middle zone consisting of columnar titanium silicides in phase TiAl3 matrix/the inner zone consisting of TiAl2 phase. In oxidation test, the much smaller increase of the mass has been observed, as a result of the coating deposition. The smallest mass changes have been detected in samples containing the coatings formed from 12.5% Si slurries. Research limitations/implications: The discussed research proves that main reason of much better oxidation resistance of TiAlSi coated base alloy is related to rich in aluminium TiAl3 phase presents in coating modified by Si. In addition silicon decrease activity of titanium, and in consequence the susceptibility of Al to selective oxidation is much stronger. The presents of Si due to Ti-Si phase generation with high oxidation resistance. Practical implications: The slurry method can be applied in aerospace and automotive industry as low-cost technology of producing of aluminide coatings on intermetallics. Originality/value: New method of aluminide coatings deposition on TiAl alloys.

10

Wpływ temperatury prasowania na mikrostrukturę i wybrane właściwości kompozytu zawierającego aluminidki żelaza

Olszówka-Myalska A., Konopka K., Przeliorz R.

Kompozyty

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2004

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R. 4, nr 12

359-362

PL

Przedstawiono wyniki badań wpływu temperatury jednoosiowego prasowania w zakresie 560-630°C na mikrostrukturę kompozytu otrzymanego z mieszaniny proszków Al i Fe oraz takie właściwości, jak: gęstość, twardość, moduł Younga E oraz moduł Kirchhoffa G. Metodą SEM stwierdzono transformację proszku żelaza w aluminidek żelaza w wyniku prasowania na gorąco. Morfologia aluminidku żelaza była zależna od temperatury prasowania - w materiałach prasowanych w zakresie 560-600°C cząstki charakteryzowała budowa zwarta, a w materiałach prasowanych w zakresie 620-630°C zdyspergowana. Stwierdzono wzrost gęstości, twardości i modułów E i G w funkcji temperatury prasowania.

EN

The composite sinters obtained from aluminium powder (Fig. 1a) and iron powder (Fig. 1b) mixture as a result of hot pressing in vacuum in Degussa press at a temperature range 560-630°C were investigated. All sintered materials were obtained from the powders mixture of composition of Al 90 vol.% and Fe 10 vol.%. The pressure 15 MPa and sintering time 30 min were used. The results of differential thermal analyse (DTA) of a mixture of aluminium powder and iron powder showed interaction between components (Fig. 2) below aluminium melting point. Microstructure observation of a composite samples by SEM Hitachi-42008 showed in aluminium matrix the presence of iron aluminides particles formed as a result of interaction between iron powder and matrix (Figs. 3-6). Differences of particles microstructure were noticed. In materials hot pressed at a temperature range 560-600°C, the intermetallic particles were globular, with shape similar to the precursor iron powder, and they increased with a temperature increase. In materials hot pressed at a temperature of 620 and 630°C a new phase was disspersed. The experiment showed the possibility of in situ formation of iron aluminide with a different morphology in aluminium matrix composite. The increase of density, hardness, Young modulus E and Kirchhoff G modulus with hot pressing temperature was stated (Table 1).

11

Crystal Structure of the New Ternary Th2Ni17-Type Related Compounds in the R-Mn-Al Systems (R=Gd, Tb, Dy, Ho, Er)

Kotur B, Palasyuk A.M.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 5

633--637

EN

New hexagonal ternary phases R2-yMnzMnxAl17-x have been obtained in the Mn-rich regions of the R-Mn-Al (R = Gd, Tb, Dy, Ho, Er) systems: Gd2-yMnxAl17-x (0_y_0.15, 13.0 _x_ 15.1); Tb2-yMnxAl17-x (0_ y_0.23, 13.2_x_15.2); Dy2-yMnxAl17-x (0_y<~0.2, 11.9_x _14.6); Ho2-yMnxAl17-x (0_y<~0.2, 11.5_x_14.2) and Er2-yMnzMnxAl17-x (0_y_0.27, 0_ z_0.54, 11.3_x_14.1). Th2Ni17-type of structure occurs in alloys with the content of R = 10.5 at.% (ideal R2X17 stoichiometry). When R < 10.5 at.%, two ways of structure constitution are possible: i) formation of the Th2Ni17- type structure with defective 2(b) atomic position (solid solution of subtraction); ii) formation of the Th2Ni17-related type structure with the substitution of part of R atoms by the Mn-Mn pairs (solid solution of multiple substitution).