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Superalloys used in aeroengines are designed to offer superior strength at increasingly higher operating temperatures. In order to optimise the working efficiency and provide additional protection to the components such as turbine blades; a thermal barrier coating (TBC) system is applied. The TBC is a multilayer system consisting of mainly two layers i.e. bond coat (BC) and topcoat (TC). In addition, a third layer grows between the TC and BC during oxidation known as a reaction layer or thermally grown oxide (TGO). The function of the TC (usually, yttria stabilised zirconia (YSZ)) is to provide thermal insulation to aeroengine parts or reduce their surface temperatures; whereas, the BC provides binding between the TC and the substrate, and oxidation resistance to the underlying alloy by forming an adherent and continuous oxide i.e. α-Al2O3. During service, in the absence of mechanical damage to the TBC, most failures are attributed to the BC performance. The most frequently adopted BCs are; β-(Pt, Ni)Al, Pt-γ-Ni/γ’-Ni3Al and MCrAlY. In addition, reactive elements (REs) are incorporated in the BCs due to their ability to enhance oxidation resistance significantly. In the present study βNiAl based coatings/BCs and alloys with and without REs (Zr and Hf) and Pt were prepared. For the coatings CMSX-4 single crystal superalloy was used as a substrate material and pack aluminising/cementation or in-situ chemical vapour deposition (CVD) as a coating process. The isothermal oxidation testing was carried out at 1150oC for 50 and 100 hours in air. The preparation and oxidation performance of a δNi2Al3 coating was carried out, as, this is a starting material for βNiAl matrix based coatings/or BCs. The oxidation of δNi2Al3 coating showed large volumetric changes (thickness variations), multiphase TGO, TGO/coating interface melting and spallation during oxidation. In contrast, the ‘simple βNiAl’ coating (or βNiAl matrix) was found to exhibit comparably enhanced thermal stability than that of the δNi2Al3 coating. Moreover, a detailed study of the simple βNiAl coating was also carried out in order to understand the oxidation performance. The coating before oxidation in the as-deposited condition was found to contain residual compressive stresses of 140 – 200 MPa. In contrast, after oxidation analysis exhibited substantial interdiffusion between the coating and the substrate resulting in a large reduction of the Al content and influx of substrate elements into the coating. This in turn caused coating transformation from βNiAl to the γ’-Ni3Al phase and formation of a multiphase TGO (TiO2, NiAl2O4, and ϴ-Al2O3 intrusion in α-Al2O3). Moreover, the degree of the TGO spallation and residual stresses increased with the oxidation time. In order to enhance the oxidation performance of the βNiAl coatings, the substrate pre-treatment was carried out i.e. CMSX-4 superalloy was electrolytically etched to remove the γ-Ni phase and fabricate βNiAl coatings on the remaining γ’-Ni3Al. This coating is termed as E-βNiAl. In comparison to simple βNiAl, the E-βNiAl coating showed improved spallation resistance. However, E-βNiAl revealed increased surface area due to etching of the substrate and triggered fast TGO growth rates when tested in an un-polished condition. Furthermore, simple βNiAl coatings were doped with Zr and Hf separately using a two-step aluminising method. The appropriate addition of either Zr or Hf was found to reduce the substrate elements (W, Ta, Cr and Ti etc.) in the coating before and after oxidation. After oxidation, examination of the presence of Zr or Hf in the coating was found to confirm the commonly reported beneficial effects. The TGOs grown on these coatings were almost pure α-Al2O3 which subsequently reduced growth and stresses. In addition to Zr/& Hf doped coatings, a study on Hf and Zr doped βNiAl bulk alloys was also carried out in order to understand the dopant effects on the oxidation resistance of βNiAl alloys in the absence of interdiffusion (as in case of coatings). In general, the commonly reported oxidation benefits were confirmed by the addition of these elements such as reduced TGO growth, oxide pegging, a columnar morphology of the TGO and segregation of REs at alumina grain boundaries etc. In addition, two more beneficial effects are suggested to be the ‘TGO crack filling up (or crack-healing)’ and formation of the ‘dense-TGO’. Within this study, the investigation of commercially available Pt-βNiAl BC was also carried out in air and vacuum atmospheres. The results demonstrated that the initial chemistry and elemental distribution (particularly Al/& Pt) was found to affect the TGO growth and phases significantly. In addition to its well established beneficial effects, the main effect of a Pt addition is suggested to be the stabilisation of the βNiAl structure even at a lower Al content.

Made available in DSpace on 2016-12-08T17:19:19Z (GMT). No. of bitstreams: 1 Cleber P Fenili.pdf: 5079728 bytes, checksum: e3ab5832297ac591534e15390527a095 (MD5) Previous issue date: 2013-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work is a study of the behavior of iron and nickel aluminides, since the high energy milling until the consolidation. Particle size and morphology of aluminides after milling and heat treatment were evaluated. A high energy milling with predetermined time and speed along with a defined stoichiometry of elemental powders were thus directed in order to obtain the intermetallic Fe3Al and Ni3Al. By obtaining the intermetallic was studied consolidation processes. The consolidation has great influence on the mechanical and microstructural properties of aluminides, motivating in recent years the study of consolidation as the density x porosity relationship. With the consolidation processes defined, which evaluates the influence of temperature, time, velocity, pressure and atmosphere. The sintering process, sintering and hot forming (S-HP) and hot pressing assisted field (FAHP) were used. The materials obtained after the consolidation processes were evaluated for density, hardness, formation of other phases and oxidation. These properties were evaluated by optical microscopy, scanning electron microscopy, vickers hardness, density, semiquantitative analysis (EDS) and X-ray diffraction. The results showed that the process FAHP is effective in consolidating the iron aluminides and nickel, for resulted in greater densification and therefore a good hardness confirming other studies using similar processes. The other cases in this study had less impressive results when compared to process FAHP, but compared to other references are considered suitable. / Neste trabalho foi realizado um estudo do comportamento dos aluminetos de ferro e níquel, desde a moagem de alta energia até a consolidação. Avaliou-se o tamanho das partículas e morfologia dos aluminetos após a moagem e tratamento térmico. A moagem de alta energia com tempo e velocidade pré determinados juntamente com uma estequiometria dos pós elementares definidos, foram assim direcionados com o intuito de obter os intermetálicos Fe3Al e Ni3Al. Com a obtenção dos intermetálicos estudou-se os processos de consolidação. A consolidação possui grande influência nas propriedades mecânicas e microestruturais dos aluminetos, motivando nos últimos anos o estudo dos processos de consolidação quanto a densidade x porosidade. Com os processos de consolidação definidos, avaliou-se a influência da temperatura, tempo, velocidade, atmosfera e pressão de compactação. Foram utilizados os processos de sinterização, sinterização e conformação a quente (S-HP) e prensagem a quente assistida por campo (FAHP). Os materiais obtidos após os processos de consolidação foram avaliados quanto a densidade, dureza, formação de outras fases e oxidação. Estas propriedades foram avaliadas através das metalografias mediante microscopia óptica, microscopia eletrônica de varredura, microdureza vickers, densidade, análise semiquantitativa (EDS) e difratometria de raios-X. Os resultados mostraram que o processo FAHP é eficaz na consolidação dos aluminetos de ferro e níquel, pois resultou em maior densificação e, por conseguinte uma boa dureza comparando com outros estudos utilizando processos parecidos. Os outros processos deste estudo obtiveram resultados menos expressivos quando comparados ao processo FAHP, porém comparados a outras referências são considerados adequados.

Etwa 27000 Flugzeuge durchqueren täglich den Luftraum über Europa. Dieser weiter steigende Flugverkehr erfordert neue Richtlinien für die Luftfahrzeuge. Im Besonderen stehen CO2- und NOX-Emission, Kerosinverbrauch und Lärmbelastung unter Optimierungsbedarf. Diese Anforderungen wurden bis 2050 vom Advisory Council for Aerospace Research in Europe (kurz: ACARE) festgelegt und werden wissenschaftlich unterstützt [3, 4]. Um diese Ziele zu erreichen, gibt es verschiedene Forschungsprogramme, Clean Sky ist ein EU-Technologieprogramm davon. In diesem Projekt werden sechs Demonstrator-Programme entwickelt, von denen MTU Aero Engines eines gestaltet. Im Rahmen dieses Projektes wurde eine Weiterentwicklung des Getriebefan (Geared Turbofan-GTF) erreicht, bei dem Fan und Niederdruckturbine durch ein Getriebe voneinander entkoppelt sind. Durch die optimierte Drehzahl beider Komponenten (vergrößerter Fan - langsamer, Niederdruckturbine (LPT) - schneller) wird die Turbinenleistung gesteigert und gleichzeitig die Geräuschemission minimiert. Entwickelt wurde der GTF von Pratt & Whitney in Kooperation mit MTU Aero Engines. Herkömmliche Varianten sehen vor, dass die Niederdruckturbine u.a. den Fan antreibt und zwar nur so schnell, dass der äußere Radius des Fans die zulässige Geschwindigkeit nicht überschreitet. Die herkömmlich verwendeten Nickelbasislegierungen in der Niederdruckturbine haben mit 8 g/cm3 eine zu hohe Dichte um einige Anforderungen im ACARE wirtschaftlich erfüllen zu können. Bereits 1967 hat die US Airforce das große Potential zur Gewichtsreduzierung durch Titanaluminid-Legierungen (TiAl-Legierungen) mit einer Dichte von rund 4 g/cm3 im Hochtemperaturbereich der Flugzeugtriebwerke erkannt. Zwischen 1980 und 1990 entwickelte das General Electric-Forschungscenter die gamma-TiAl-Legierung Ti-48Al-2Cr-2Nb, welche als erste kommerzielle Titanaluminidlegierung in der Niederdruckturbine von Flugzeugtriebwerken eingesetzt wurde. Eine weitere Legierung dieser Werkstoffgruppe kam erst ca. 15 Jahre später zum Einsatz, die TNM-Legierung. Wie man an diesem Beispiel sehen kann, dauert die Integration neuer Werkstoffe in der Luftfahrt aufgrund der notwendigen Vorversuche und Sicherheitsaspekte teilweise 20 Jahre. Seit September 2014 kommt im Triebwerk PW1100G GTF von Pratt & Whitney die geschmiedete Version der TNM-Legierung zum Einsatz. MTU Aero Engines AG München baut hierfür die Niederdruckturbine. Durch die hervorragenden Hochtemperatureigenschaften der gamma-TiAl-Legierungen wie z.B. thermische Stabilität der Mikrostruktur, Resistenz gegen Titanfeuer und hohe spezifische Fes-tigkeit, konnten sich die Titanaluminide in Konkurrenz zu den Nickelbasislegierungen sehr gut platzieren. Deswegen werden die beiden gamma-TiAl-Legierungen (Ti-48Al-2Cr-2Nb, TNMTM) bereits in den letzten Stufen der Niederdruckturbine eingesetzt. Ein Nachteil der gamma-Titanaluminide ist die begrenzte Oxidationsbeständigkeit über 750 °C, wodurch das Einsatzfeld als Hochtemperaturwerkstoff stark begrenzt wird. Um das Anwen-dungspotential der gamma-Titanaluminide weiter zu steigern und auch bei Temperaturen über 750 °C einzusetzen, ist eine Steigerung der Oxidationsbeständigkeit notwendig. Die Oxidationsbeständigkeit kann durch das Aufbringen von Oxidationsschutzschichten wie z.B. Al2O3 erreicht werden. Welche neben der Korrosionsbeständigkeit auch die thermisch-mechanischen Anforderungen des Substrat-Schicht-Verbundes sicherstellen müssen. Zur Erhöhung der Temperaturbelastbarkeit von gamma-TiAl-Schaufeln können zur thermischen Isolation keramische Wärmedämmschichten (WDS) aufgebracht werden. Aufgrund der WDS können höhere Prozesstemperaturen realisiert und die Lebensdauer des Grundwerkstoffs verlängert werden. Die Lebensdauer der Wärmedämmschichten und das Betriebsverhalten werden unter anderem durch eine gute Haftung auf dem Untergrund, eine niedrige Wärmeleitfähigkeit und einen thermisch stabilen Phasenaufbau bestimmt. Die Kombination aus Oxidationsschutz und Wärmedämmung wird bereits für Nickelbasislegierungen in der Brennkammer und Hochdruckturbine der Flugzeugtriebwerke eingesetzt. Um gamma-Titanaluminide in weitere Stufen der Niederdruckturbine oder Hochdruckturbine einzubringen, müssen diese Temperaturen von mindestens 900 °C aushalten und erfordern ebenso Beschichtungen zum Oxidations- und Wärmeschutz. Diese Schutzschichten finden für gamma-Titanaluminide bisher jedoch noch keine Anwendung.

The operating efficiency and reliability of modern jet engines have undergone significant improvement largely owing to the advances of the materials science over the past 60 years. The use of both superalloys and TBCs in engine components such as turbine blades has made it possible for jet engines to operate at higher temperatures, allowing an optimal balance of fuel economy and thrust power. Despite the vast improvement in high temperature capability of superalloys, the utilization of TBCs has brought the concern of coating adhesion during their usage. TBCs are prone to spallation failure due to interfacial rumpling, which is driven primarily by thermal coefficient mismatch of the multi-layered structure. Although interfacial degradation of TBCs has been widely studied by detailed numerical and analytical models, the predicted results (i.e. stress state and rumpling amplitude) often deviate from that obtained by experiments. This is largely due to the lack of consideration of the influence of bond coat and substrate chemistry on the interfacial evolution of TBC systems. It is only in recent year that more and more study has been focused on studying the role of chemistry on the interfacial degradation of TBCs. The purpose of this PhD project is to clarify how the bond coat and substrate chemical compositions dictate the mechanisms of interfacial degradation, leading to the final spallation. A cross-sectional indentation technique was utilized to quantitatively characterize the adhesion of oxide-bond coat interface among 5 systematically prepared TBC systems. The adhesion of isothermally exposed oxide-bond coat interface was then correlated with different microstructure parameters, in an attempt to identify the key parameters controlling the TBC spallation lifetime. EBSD and EPMA analyses were conducted on the bond coat near the oxide-bond coat interface, in order to understand the relationship between the key parameters and specific alloying elements. The results clearly demonstrated that the phase transformation of bond coat near the oxide-bond coat interface plays the dominant role in the degradation of interfacial adhesion. Particularly, the co-existence of gamma prime and martensitic phases, each having very different thermomechanical response under thermal exposure, can generate a misfit stress in the TGO layer, and ultimately causes early TBC spallation. In addition, the phase transformation behavior has been closely associated with the inherent chemistry of the bond coat and substrate.

Al₃Ti, Al₅CuTi₂, and Al₆₆Mn₁₁Ti₂₃, intermetallic matrices reinforced with 30, 40, and 50 volume % TiB, have been produced by XD_™ processing and densified into bulk form by powder metallurgy techniques. The compressive flow behavior of the Al₃Ti and Al₅CuTi₂, composites have been evaluated at temperatures ranging from 1000°C to 1200°C and strain rates of 0.0001 and 0.001 sec⁻¹. The results have been analyzed by a correlation to the resulting microstructure, especially with regards to the intermetallic matrix composition, TiB₂ size, and interparticle spacing. The results of these analyses are applied to a constitutive equation based upon the flow stress equation. It has been shown that at in this temperature regime, all deformation occurs within the intermetallic matrix. This is substantiated by the lack of TiB₂-dependent behavior with variations in volume percentage of reinforcement. In all cases, the composites are readily deformed at relatively low loads. The average strain-rate sensitivity values were 0.349 for the Al₃Ti-based composites, and 0.247 for the Al₅CuTi₂, variants. The average activation energies were calculated to be 485 kJ/mol and 920 kJ/mol for the Al₃Ti-and Al₅CuTi₂-matrices, respectively. The structure constant was calculated based upon these values. The Zener-Hollomon parameter was used to plot the flow stress along lines of constant temperature and strain rate, and serves as one type of constitutive equation. In addition, the flow stress was evaluated as a function of the strain rate and temperature. These models were found to provide adequate correlation to the measured flow behavior. / Master of Science

O presente trabalho objetiva o desenvolvimento in situ por plasma por arco transferido (PTA) de aluminetos de Níquel resistentes à oxidação, baseados em uma liga NiCrAlC referência. Para tanto, foram depositadas misturas preliminares de pós elementares e também utilizando o pó atomizado, variando somente a intensidade de corrente (130 e 160 A) para se obter diferentes misturas com o substrato. Após as deposições, a incorporação de elementos do substrato nos cordões não permitiu a formação de aluminetos para os revestimentos processados com a mistura de pós elementares. Estes apresentaram valores de diluição consideravelmente maiores do que os cordões obtidos com pó atomizado, que resultaram em aluminetos de Níquel. Com base nos resultados preliminares, quatro novas composições com mistura de pós elementares foram estimadas e os cordões finais, processados com 100 ou 130 A, resultaram em aluminetos como esperado. Duas composições foram submetidas a ensaios em balança termo gravimétrica (TGA) e a ciclos isotérmicos em forno mufla para diferentes temperaturas (máximo de 1000 graus Celsius) e tempos de exposição (até 72 horas no máximo). Os resultados mostraram que a incorporação de Ferro nos revestimentos durante a deposição retardou a formação das camadas de óxidos, sendo que maiores teores deste elemento aceleraram a formação da camada de alumina alfa, o que propiciou uma redução nos valores de constante de oxidação parabólica a 1000 graus Celsius nos estágios iniciais da oxidação. Os revestimentos apresentaram melhores desempenhos à oxidação do que a liga NiAlCrC fundida, traduzido pelo menor ganho de massa. A exposição nas temperaturas de ensaio provocou uma queda de dureza e na evolução ou nucleação de uma provável fase sigma. / This research aimed at the development in situ by plasma transferred arc (PTA) of nickel aluminides resistant to the oxidation, based on a reference NiCrAlC alloy. For this purpose, preliminary mixtures of elemental powders were deposited, and also using the atomized powder, varying the current intensity (130 and 160 A) only to obtain different mixtures with substrate. After the depositions, the incorporation of substrate elements into the welds did not allow the formation of aluminides in the coatings processed with the elemental powder mixture. These coatings presented dilution values considerably higher than those obtained with atomized powder, which result in nickel aluminides. Based on the preliminary results, additional four compositions with elemental powders were estimated and the final welds, processed with 100 or 130 A, were composed by aluminides as expected. Two compositions were submitted to the thermogravimetry tests and isothermal cycles in an oven for different temperatures (1000 Celsius max) and exposure times (for 72 hours at maximum). The results showed that the iron incorporation in the coatings during depositions delayed the oxides scales formation, since higher contents of this element accelerated the formation of -alumina, which promoted a reduction in the parabolic constant of oxidation for 1000 Celsius in the earlier stages of oxidation. The coatings presented better oxidation resistance than that observed for as-cast NiCrAlC, observed by their smaller mass losses. The exposure to the testing temperatures resulted in a decrease of hardness and in the evolution or nucleation of sigma phase.

O presente trabalho objetiva o desenvolvimento in situ por plasma por arco transferido (PTA) de aluminetos de Níquel resistentes à oxidação, baseados em uma liga NiCrAlC referência. Para tanto, foram depositadas misturas preliminares de pós elementares e também utilizando o pó atomizado, variando somente a intensidade de corrente (130 e 160 A) para se obter diferentes misturas com o substrato. Após as deposições, a incorporação de elementos do substrato nos cordões não permitiu a formação de aluminetos para os revestimentos processados com a mistura de pós elementares. Estes apresentaram valores de diluição consideravelmente maiores do que os cordões obtidos com pó atomizado, que resultaram em aluminetos de Níquel. Com base nos resultados preliminares, quatro novas composições com mistura de pós elementares foram estimadas e os cordões finais, processados com 100 ou 130 A, resultaram em aluminetos como esperado. Duas composições foram submetidas a ensaios em balança termo gravimétrica (TGA) e a ciclos isotérmicos em forno mufla para diferentes temperaturas (máximo de 1000 graus Celsius) e tempos de exposição (até 72 horas no máximo). Os resultados mostraram que a incorporação de Ferro nos revestimentos durante a deposição retardou a formação das camadas de óxidos, sendo que maiores teores deste elemento aceleraram a formação da camada de alumina alfa, o que propiciou uma redução nos valores de constante de oxidação parabólica a 1000 graus Celsius nos estágios iniciais da oxidação. Os revestimentos apresentaram melhores desempenhos à oxidação do que a liga NiAlCrC fundida, traduzido pelo menor ganho de massa. A exposição nas temperaturas de ensaio provocou uma queda de dureza e na evolução ou nucleação de uma provável fase sigma. / This research aimed at the development in situ by plasma transferred arc (PTA) of nickel aluminides resistant to the oxidation, based on a reference NiCrAlC alloy. For this purpose, preliminary mixtures of elemental powders were deposited, and also using the atomized powder, varying the current intensity (130 and 160 A) only to obtain different mixtures with substrate. After the depositions, the incorporation of substrate elements into the welds did not allow the formation of aluminides in the coatings processed with the elemental powder mixture. These coatings presented dilution values considerably higher than those obtained with atomized powder, which result in nickel aluminides. Based on the preliminary results, additional four compositions with elemental powders were estimated and the final welds, processed with 100 or 130 A, were composed by aluminides as expected. Two compositions were submitted to the thermogravimetry tests and isothermal cycles in an oven for different temperatures (1000 Celsius max) and exposure times (for 72 hours at maximum). The results showed that the iron incorporation in the coatings during depositions delayed the oxides scales formation, since higher contents of this element accelerated the formation of -alumina, which promoted a reduction in the parabolic constant of oxidation for 1000 Celsius in the earlier stages of oxidation. The coatings presented better oxidation resistance than that observed for as-cast NiCrAlC, observed by their smaller mass losses. The exposure to the testing temperatures resulted in a decrease of hardness and in the evolution or nucleation of sigma phase.

Le système Ti-Al est prometteur pour la substitution aux superalliages base-Ni aéronautiques. Dans la gamme de compositions d’intérêt pour ces applications, la solidification de ces alliages débute par la phase ß (structure cubique centrée) suivie d’une transition péritectique ß + L → α (structure hexagonale). En fonction de la teneur en Al, les proportions des phases ß et α au cours de la solidification varient, et le procédé de coulée centrifuge pour fabriquer des aubes de turbine pour l’aéronautique introduit d’autres variations structurales. Le présent travail explore l’influence de la teneur en Al et de la centrifugation sur la solidification de ces alliages. Des expériences de refusion en creuset froid sous induction, de solidification dirigée en centrifugeuse de grand diamètre et de coulée centrifuge sont présentées et caractérisées. Des mécanismes potentiels pour les différences structurales observées sont proposés. Une fragmentation assistée par une teneur en Al plus élevée est observée dans les essais en creuset froid, et une réaction péritectique démarrant plus tôt est associée à une fragmentation plus efficace pour provoquer la transition colonnaire-équiaxe (TCE). Une compétition entre la convection et la sédimentation est observée lors des essais de solidification dirigée sous centrifugation, et la refusion des bras secondaires est responsable de la TCE. En coulée centrifuge, des structures hétérogènes en « ailes de mouette » à faibles teneurs en Al dépendent de la cinétique de refroidissement et de la convection. Un comportement différent sous les mêmes conditions est constaté à plus fortes teneurs en Al, transition qui semble coïncider avec le péritectique / The Ti-Al system is a promising substitute for Ni-based aeronautical superalloys. In the composition range of interest for these applications, the solidification of these alloys begins with a ß phase (body-centered cubic structure) followed by a peritectic transition ß + L → α (hexagonal close-packed structure). As a function of Al content, the proportions of ß and α phases over the course of solidification change, and the centrifuge casting process for aeronautical turbine blade fabrication introduces other structural variations. The present work explores the influence of Al content and centrifugation on the solidification process in these alloys. Remelting experiments in a cold-crucible induction furnace, directional solidification experiments in a large-diameter centrifuge and centrifuge casting experiments are presented and characterized. Potential mechanisms for the observed structural differences are proposed. Fragmentation assisted by a higher Al content is observed in cold crucible casting, and an early onset of the peritectic reaction is associated with fragmentation that more effectively provokes a columnar-to-equiaxed transition (CET). Competition between convection and sedimentation is observed in directional solidification under centrifugation, and secondary arm remelting is responsible for CET. In centrifuge casting, heterogeneous “seagull wing” structures for low Al contents depend on cooling rates and convection. A different behavior under the same conditions is noted for higher Al contents, and the transition seems to coincide with the peritectic

La première partie de ce manuscrit est consacrée à l’étude des microstructures et des microségrégations, héritées de la solidification des alliages ternaires Fe-Al-Ti, Fe-Al-Zr et quaternaires Fe-Al-Ti-Zr. Pour améliorer la compréhension des phénomènes ayant lieu au cours de la solidification et disposer d’un outil permettant de prédire les phases formées au cours de la solidification, une description thermodynamique du coin riche en fer du système quaternaire Fe-Al-Ti-Zr est proposée dans une seconde partie. A partir de l’ensemble des données expérimentales et bibliographiques disponibles concernant les équilibres de phases dans les différents systèmes ternaires, une description thermodynamique de chacun des systèmes ternaires est effectuée. Les systèmes Fe-Al-Zr et Fe-Ti-Zr ont été complètement décrits à l’aide du logiciel ThermoCalc. Le système ternaire Fe-Al-Ti a fait l’objet d’une description partielle. Les résultats obtenus permettent de proposer une première description thermodynamique du coin riche en fer du système quaternaire Fe-Al-Ti-Zr. Des séquences de solidification ont également été calculées à partir de cette description pour les alliages ternaires Fe-Al-Zr et quaternaires Fe-Al-Ti-Zr et comparées aux résultats expérimentaux / The first part of this work deals with the study of the microstructures and micro-segregations phenomena, inherited from the solidification on Fe-Al-Ti, Fe-Al-Zr and Fe-Al-Ti-Zr alloys. To improve our understanding of the phenomena occurring during the solidification process and to dispose of a predictive tool of the phases formed during the solidification process, a thermodynamic modeling of the iron rich corner of the Fe-Al-Ti-Zr quaternary system is proposed on a second part. From the data available in this work and in the literature, a thermodynamic modeling of each of the constituting ternaries systems is performed. Fe-Al-Zr and Fe-Ti-Zr ternaries systems were fully modeled using the ThermoCalc software. The Fe-Al-Ti ternary system is only partially modeled. These results allowed us to propose a first description of the iron rich corner of the Fe-Al-Ti-Zr quaternary system. Solidification sequences were calculated from this thermodynamic model for Fe-Al-Zr ternaries and Fe-Al-Ti-Zr quaternaries alloys and compared to our experimental results