To see the other types of publications on this topic, follow the link: Intermetallic phases.
Dissertations / Theses on the topic 'Intermetallic phases'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Intermetallic phases.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Klepser, Cheryl Ann. "Growth of intermetallic phases at low temperature." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38762.
Full text
2
Chen, Chun-Liang. "Characterisation of intermetallic phases in multicomponent Al-Si alloys for piston applications." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7834.
Full textAbstract:
Al-Si based casting alloys are widely used for piston applications. This is due to their combination of properties, which include good castability, high strength, light weight, good wear resistance and low thermal expansion. In order for such alloys to meet increasingly demanding operational requirements, such as higher service temperatures and pressures, multicomponent Al-Si alloys, which contain several other alloying additions (Cu, Ni, Mg, Mn and Fe), have been used to further enhance the high temperature strength and fatigue resistance. Improved material properties are strongly dependent upon the morphologies, the thermal and mechanical properties, and the distribution of the intermetallic phases present in these alloys, which are in turn a function of alloy composition and cooling rate. Therefore, the main aim of this work was to characterise the many complex intermetallic phases in multicomponent Al-Si alloys. Five main areas of interest were investigated in this research. Firstly, thermodynamic modelling has been used to predict phase formation in complex alloys, which has been compared with measurements from differential scanning calorimetry (DSC). Secondly, the presence of additional elements in multicomponent Al-Si alloy systems allow many complex intermetallic phases to form, which make microstructural characterisationn on-trivial, as some of the phases have either similar crystal structures or exhibit subtle changes in their chemistries. A combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray analysis (EDX) have therefore been used for discrimination between the various phases. It is shown that this is a powerful technique for microstructure characterisation and provides detailed information which can be related to the microstructuree volution during initial casting and subsequent heat treatment. Additionally, the complex morphologies of intermetallics have also been observed using 3D X-ray tomography. In this present work, a number of different experimental techniques were used to provide a rapid means of phase discrimination in order to validate microstructural evolution models. Thirdly, the mechanical properties of individual intermetallics have been investigated as a function of temperature using high -temperature nanoindentation. In particular, the hardness and modulus of a number of phases have been measured for a range of alloy compositions. The creep behaviour of intermetallic phases was also investigated, since this is important in the determination of the high temperature mechanical properties of alloys. Fourthly, the coefficients of thermal expansion of intermetallic phases were measured by high temperature X-ray diffraction, and thermal expansion anisotropy was also explored to investigate the formation of microcracking. Finally, in order to investigate the effect of both applied mechanical and thermal loads on the formation of cracks, Eshelby modelling has been used to predict the internal stresses of the different intermetallic phases and alloys, with the aid of the experimental data obtained in this work. The phase identity, composition, and the corresponding physical and mechanical properties can be used to inform alloy design strategies which, may facilitate the development of new alloys with improved properties.
3
Eurich, Nikolai Carl. "First principles investigation of intermetallic phases and defects in Ni-base superalloys." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709196.
Full text
4
Matsumoto, Jun. "Electrochemistry of intermetallic phases of Ni-Cr-Fe alloys in aqueous environment." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13439.
Full text
5
Atteberry, Jennifer Eve. "A resonant ultrasound spectroscopy study of hydrogen-absorbing intermetallic compounds." Access citation, abstract and download form; downloadable file 11.43 Mb, 2004. http://wwwlib.umi.com/dissertations/fullcit/3131654.
Full text
6
Reeder, Andrew J. "An investigation of aluminium intermetallic phases using ⁵⁷Fe Mössbauer spectroscopy and complementary techniques." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/20269/.
Full textAbstract:
Pure intermetallic compounds Al3Fe, AlmFe, AlxFe, ac-AlFeSi, and Al6(Fe,Mn) have been extracted from Bridgman grown model aluminium alloys by dissolving the aluminium matrix in butanol. The resultant transmission Mdssbauer spectra for each intermetallic compound were interpreted according to their crystal structure. Variable temperature 57Fe Mdssbauer studies have enabled the Debye temperature thetaD of each compound to be determined. The crystal structure of Al3Fe contains five different Fe sites within the unit cell. Four of the iron, Fe(l)-Fe(4), sites are approximately identical and produced a thetaD = 434 +/- 5 K. The remaining Fe site, Fe(5), produced a thetaD = 488 +/- 5 K, and the combined spectral areas a 3D = 452 +/- 5 K. There is only one individual site within the crystal structures of AlmFe, AlxFe, and Al6(Fe,Mn), which produced a thetaD of 358 +/- 5 K, 360 +/- 5 K, and 352 +/- 5 K respectively. The ternary intermetallic compound, ac-AlFeSi, has two different Fe sites within the unit cell. Fe(l) had a thetaD - 291 +/- 5 K, and Fe(2) thetaD = 329 +/- 5 K. The combined spectral areas of these two sites produced a thetaD = 311 +/- 5 K. The variation in the OD values was attributed to changes in the Al-Fe shortest bond within the Fe centred A1 polyhedra. The Fe centred A1 polyhedra are a common feature of all the intermetallic compounds studied. The iron atom in all the intermetallic compounds may have existed in a Fe2+ oxidation state. A Direct Chill-cast ingot was grown and two samples, A and B, were taken from regions within the ingot containing a mixture of two intermetallic compounds. Alloy sample A was found to contain the intermetallic compound combination Al3Fe + Al6Fe. The intermetallic combination Al6Fe + ac- AlFeSi was found to exist in alloy sample B. Transmission Mdssbauer spectroscopy was performed on the extracted phases and the insitu phases to determine the relative proportions of the intermetallic compounds within the two alloy samples. Alloy sample A had 50:50 +/- 5 % Al3Fe + Al6Fe, whereas alloy sample B had 30:70 +/- 5 % Al6Fe + ac-AlFeSi. The surface of alloy sample B was investigated using several surface techniques, CEMS, SAAES, and SAXPS, to determine whether the same relative proportions existed in the surface, and near surface, regions of the sample. A region of very fine amorphous iron super-paramagnetic grains were to dominate the near surface region of the sample, which was present due to selective oxidation of the Al6Fe intermetallic compound. This was then removed when the surface of the alloy sample was KI electro-etched, which had the effect of leaving the intermetallic particles standing proud of the surface. The CEMS technique identified that the Al6Fe + ac-AlFeSi existed in a 80:20 +/- 5 %. This change in phase ratio after the KI electro-etch process was attributed to the preferential etching of the ac-AlFeSi aluminium intermetallic compound.
7
Gunn, Robert Neil. "The effect of thermal cycles on the microstructure and toughness of superduplex stainless steels." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/8418.
Full text
8
Heymann, Gunter. "Synthetic Investigations in Borates, Borate Germanates, Gallium Oxonitrides, and Intermetallic Phases at Extreme Conditions." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-75784.
Full text
9
Roberts, Tracey. "The structure and stability of high temperature intermetallic phases for application within coating systems." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4499.
Full textAbstract:
The reduction of noise and emissions is becoming increasingly important in civil aircraft jet engines as well as requirements for reduced fuel consumption and improved efficiency. This has resulted in the drive towards increasing turbine entry temperatures and the development of thermal barrier coatings (TBCs). Due to the effectiveness of the platinum-modified nickel aluminides currently used as bond coat layers for Ni-based superalloy TBCs, higher temperature ruthenium-containing bond coat layers are being examined as a possible low cost alternative to platinum. Rolls Royce have a patented process, whereby precious metal layers directly react with single crystal substrate alloys to form an aluminium containing surface coating. The aluminium is sourced from the single crystal alloy and the coating so formed has a + structure, but contains other intermetallic phases due to the reaction between the coating and the single crystal substrate. This bond coat layer acts as a diffusion barrier, which limits interdiffusion between the coating and the substrate. The aim of this research was to examine the stability of various phases within platinum and ruthenium-containing multilayer systems formed during the above reaction process and to determine the most stable intermetallics for inclusion in future coating systems. Foil samples were manufactured using multilayer sputter coating methods and the exothermic formation of these phases was examined using differential scanning calorimetry. The identification of the phases formed was carried out using X-ray diffraction. It was found that the interdiffusion between the initial multi-layers had been incomplete during the samples heat treatment, and so more intermetallic phases formed in some samples than aimed for. Hence, from the large number of samples studied it was shown that, as a result of kinetic factors, the reaction onset (or trigger) temperature was not related to the enthalpy of the intermetallic phases formed or the sample compositions within a target phase field. For the β-phase (NiAl) type intermetallic systems, the samples that produced the highest enthalpy values (i.e. the most stable intermetallic compounds) were those with the nominal compositions (in atomic %) of; ‘47Ni53Al’, ‘48Ni6Pt46Al’ and ‘51Ni7Ru42Al’. For the γ΄-phase (Ni3Al) type intermetallic systems, the highest enthalpy values were from samples with nominal compositions of ‘60Ni16Pt24Al’ and ‘74Ni5Ru24Al’
10
Kaganovskii, Yuri, Lyudmila N. Paritskaya, and Valeriy V. Bogdanov. "Lateral diffusion spreading of two competitive intermetallic phases along free surface (system Cu-Sn)." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193701.
Full text
11
Schopf, Daniel Verfasser], and Hans-Rainer [Akademischer Betreuer] [Trebin. "Effective potentials for numerical investigations of complex intermetallic phases / Daniel Schopf. Betreuer: Hans-Rainer Trebin." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2013. http://d-nb.info/1036132307/34.
Full text
12
Bhowmik, Ayan. "Refractory metal laves phase alloys based on the Cr-Ta system." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607770.
Full text
13
Bernard, Christopher. "Capacity Fade Studies in LixSi, LixGe, LixAl, and LixSn Electrodes." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574462338470697.
Full text
14
Tambornino, Frank [Verfasser], and Wolfgang [Akademischer Betreuer] Schnick. "Electrolytic Synthesis and structural chemistry of intermetallic phases with polar metal-metal bonding / Frank Tambornino ; Betreuer: Wolfgang Schnick." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1124779957/34.
Full text
15
Silva, Campos Maria del Rosario [Verfasser]. "The role of intermetallic phases in the corrosion of magnesium-rare earth alloys / Maria del Rosario Silva Campos." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2016. http://d-nb.info/1114820385/34.
Full text
16
Pillaca, Quispe Mirtha [Verfasser], and Peter [Akademischer Betreuer] Gille. "Single crystal growth and structural characterization of intermetallic phases for thermoelectric applications / Mirtha Pillaca Quispe ; Betreuer: Peter Gille." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1225682754/34.
Full text
17
Oh, Minseok. "Growth kinetics of intermetallic phases in the Cu-Sn binary and the Cu-Ni-Sn ternary systems at low temperatures." access full-text online access from Digital Dissertation Consortium, 1994. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?9513132.
Full text
18
Bysakh, Sandip. "Pulsed Laser Ablation Deposition of Intermetallic Thin Films: A Study of Evolution of Metastable Phases and Ultra-fine Microstructures." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/135.
Full textAbstract:
This thesis is devoted to the deposition of intermetallic thin films by laser ablation deposition (LAD) and their characterization. Pulsed laser ablation and subsequent deposition of the ablated vapours produces films under conditions very far away from equilibrium. Besides the film, which forms directly by quenching the vapour or plasma on substrate, one also obtains under certain conditions micron and sub-micron sized spherical droplets of alloy melt on to the film. The latter travel at very high velocities and impinge on the substrate resulting in a very high rate of heat transfer during solidification from liquid state. Therefore, in this work it was possible to study the microstructure evolution depending on quenching rates of different sized droplets and compare with the extreme case of vapour/plasma quenching.
The compositions selected correspond to the intermetallic compounds in Al-Fe, Al-Ni and Ti-Si binary systems. Pre-alloyed targets of the appropriate intermetallic compositions were used for ablation by laser. The deposition system has been designed and built in-house. The
characterization is mainly done by transmission electron microscopy (TEM). The study focuses on microstructure and phase evolution within these intermetallic films at room temperature, at elevated temperature and during heating the room temperature deposited films in heating stage inside the TEM.
19
Bysakh, Sandip. "Pulsed Laser Ablation Deposition of Intermetallic Thin Films: A Study of Evolution of Metastable Phases and Ultra-fine Microstructures." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/135.
Full textAbstract:
This thesis is devoted to the deposition of intermetallic thin films by laser ablation deposition (LAD) and their characterization. Pulsed laser ablation and subsequent deposition of the ablated vapours produces films under conditions very far away from equilibrium. Besides the film, which forms directly by quenching the vapour or plasma on substrate, one also obtains under certain conditions micron and sub-micron sized spherical droplets of alloy melt on to the film. The latter travel at very high velocities and impinge on the substrate resulting in a very high rate of heat transfer during solidification from liquid state. Therefore, in this work it was possible to study the microstructure evolution depending on quenching rates of different sized droplets and compare with the extreme case of vapour/plasma quenching.
The compositions selected correspond to the intermetallic compounds in Al-Fe, Al-Ni and Ti-Si binary systems. Pre-alloyed targets of the appropriate intermetallic compositions were used for ablation by laser. The deposition system has been designed and built in-house. The
characterization is mainly done by transmission electron microscopy (TEM). The study focuses on microstructure and phase evolution within these intermetallic films at room temperature, at elevated temperature and during heating the room temperature deposited films in heating stage inside the TEM.
20
Yu, Jiamin [Verfasser], John [Akademischer Betreuer] Banhart, John [Gutachter] Banhart, and Dieter [Gutachter] Herlach. "Formation of intermetallic phases in Al-10Si-0.3Fe based alloys / Jiamin Yu ; Gutachter: John Banhart, Dieter Herlach ; Betreuer: John Banhart." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156347130/34.
Full text
21
CARLINO, Francesco. "Influenza degli elementi di lega nei bagni di zincatura sulla formazione delle fasi intermetalliche e sulla resistenza a flessione dei rivestimenti a caldo." Doctoral thesis, Università degli studi di Cassino, 2021. http://hdl.handle.net/11580/83827.
Full textAbstract:
In almost all industrial applications metallic materials are the most widely used and they are employed in a wide range of applications. These materials work in continuous contact with the surrounding environment; in fact, in this environment they fulfil the functions for which they are designed and manufactured.
The interaction between the metallic material and the environment in which it operates is a chemical one and it is known as corrosion. Hot-dip galvanising is the most effective and widely used protection technique against corrosion. This technique is valuable because it has a dual action: firstly, a barrier is created that insulates the metal from the aggressive environment, and secondly, the zinc in the coating has a lower electrochemical potential than iron; therefore, the substrate is protected by the Zn-based coating even if this latter is damaged. The relationship between the mechanical properties of the coating and the parameters of the hot dip galvanising process can be understood by analysing the kinetics of coating developments. Indeed, the mechanical characteristics can be profoundly modified by intermetallic phases. For this reason, to supervise the phases present in the composition of the coating is necessary for improving the mechanical properties. In the scientific literature, there are some models that consider the kinetic development of intermetallic phases. Considering both the phenomena of interdiffusion between zinc and iron atoms, and the stability of the phases for a precise chemical composition, to anticipate the thickness of the phase is substantial. The formation and propagation of cracks can be anticipated through a damage model, which should be developed by analysing the damage micro-mechanisms of the intermetallic phases.
In this activity, the hot dip galvanizing process was applied to low carbon steel samples, considering different bath compositions. Then, the obtained coatings were studied by optical microscopy, analysing and identifying the formation of different intermetallic phases, depending on the composition of the bath. After, bending tests were carried out in the laboratory using the Duncan mechanism, which was suitably mounted on a 100 kN electromechanical machine. Five different protective zinc coatings were characterised and compared, which derived from immersion in different baths. Specifically, the five baths used were: pure Zn, Zn - Pb 1%, Zn - Al 5%, Zn - Sn 3% and Zn - Ti 0.5%; moreover, five different immersion times were considered: 15, 60, 180, 360 and 900 seconds. The temperature used in the galvanizing phase was instead kept constant at about 460 °C for all the investigated conditions. The obtained thicknesses and the various damage caused by the stress were then compared and analysed, through various comparisons carried out by means of optical microscope observations on the sections of the different galvanised specimens. Therefore, through this study, it was possible to identify the various damage mechanisms of the intermetallic phases as a function of the dipping time and the bath composition. It was found that the damage mechanisms were mainly represented by nucleation and growth of radial cracks in correspondence of the hardest and most fragile phases of the coating. It was also possible to evaluate the importance of ductile phases presence and how their thickness growth tended to stop the propagation of defects. Finally, replacing toxic elements such as Lead in favour of elements such as Tin, Aluminium and Titanium was preliminary evaluated; however, further studies are necessary in order to improve the homogeneity and uniformity of the zinc coating for avoiding possible problems of coating adhesion and detachment.
22
Tardelli, Joffrey. "Etude du comportement électrochimique des phases intermétalliques des alliages d'aluminium 2214-T6 et 7050-T74 : approche multi-échelle de matériaux polyphasés." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0082/document.
Full textAbstract:
L'étude du comportement électrochimique des phases intermétalliques Al2Cu, Al2CuMg, Al7Cu2Fe, (Al,Cu)16Mn4Si3 et MgZn2, caractéristiques des alliages d'aluminium 2214-T6 et 7050-T74 et réalisée à partir d'échantillons massifs synthétisés, a montré que la formation de défauts majeurs dans la couche d'oxyde, obtenue par anodisation des alliages en milieu H2SO4 200 g/l, était directement due à la présence de ces particules au sein des alliages. L'important dégagement gazeux d'oxygène qui se produit à la surface de ces particules lors de l'étape d'anodisation explique la formation de trous et de fractures dans la couche d'oxyde. En milieu marin, ces défauts facilitent la migration des ions chlorures à la surface de l'alliage mise à nu localement et favorisent par conséquent le développement de la corrosion localisée. Les résultats obtenus en milieu NaCl 35g/l ont permis de mieux comprendre le mécanisme de corrosion des phases intermétalliques ainsi que leur rôle sur la propagation des piqûres. L'élimination des particules intermétalliques de la surface des alliages lors de l'étape de décapage (avant anodisation) permet de favoriser une croissance plus régulière de la couche d'oxyde lors de l'anodisation. Par conséquent, la résistance à la corrosion des alliages 2214 et 7050 augmente considérablement, permettant d'atteindre les objectifs fixés lors de ce projetThe electrochemical behaviour of the bulk intermetallic particles such as Al2Cu, Al2CuMg, Al7Cu2Fe, (Al,Cu)16(Mn,Fe)4Si3 and MgZn2 showed that the formation of wide defects in the oxide layer during the 2214-T6 and 7050-T74 alloys anodization was directly due to the presence of these kind of particles in the microstructure which are able to sustain both high dissolution rate and high water oxidation kinetics in acidic electrolyte. In marine environment, these defects facilitate the migration of aggressive ions like chloride on the locally bare alloys and are the onset of the pitting corrosion. The results obtained in 3.5 wt.% sodium chloride electrolyte permit to understand the corrosion mechanism of the intermetallic phases and their influence on the pits propagation. The optimization of the alloys pickling conditions in order to remove this kind of particles (prior to the anodization step) has been investigated in this work. Consequence of removing intermetallic particles, the aluminium enrichment of the surface facilitates the oxide growth and the formation of regular layer. The corrosion tests on treated aluminium alloys have clearly showed the influence of the pickling step on the resistance corrosion of 2214 and 7050 alloys, reaching the objectives fixed in this project
23
Moura, Lorena Braga. "CinÃtica de transformaÃÃo de fases em novos aÃos inoxidÃveis superferrÃticos com alto teor de molibdÃnio." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16905.
Full textAbstract:
Pesquisas anteriores sobre aÃos ferrÃticos experimentais com alto teor de molibdÃnio (Mo) constataram que embora o Mo seja responsÃvel por aumentar a resistÃncia à corrosÃo em meios ricos em Ãcidos naftÃnicos e em complexos de enxofre, teores acima de 5% Mo favorecem a formaÃÃo de fases deletÃrias e reduzem a tenacidade do aÃo. Para melhorar a tenacidade dessas ligas, mantendo-se a estabilidade da fase ferrÃtica, o presente trabalho adicionou nÃquel (Ni) à composiÃÃo, elevou o teor de cromo (Cr) para 25% e manteve o elevado teor de Mo. Essas novas ligas pertencem a uma famÃlia de aÃos denominados aÃos inoxidÃveis superferrÃticos, desenvolvidos inicialmente para uso em trocadores de calor e ambientes marinhos. Este trabalho faz parte de um estudo para adaptar a composiÃÃo de aÃos superferrÃticos comerciais para utilizaÃÃo em plantas petrolÃferas que refinam petrÃleos ricos em compostos de enxofre atravÃs do aumento do teor de Mo na liga. A cinÃtica de precipitaÃÃo de fases em ligas com composiÃÃes experimentais (Fe25%Cr5-7%Mo2-4%Ni) com adiÃÃo de niÃbio (Nb) e titÃnio (Ti) foi estudada para temperaturas de 400ÂC a 900ÂC em diferentes tempos de tratamento. Foi realizado o estudo termodinÃmico das ligas empregando o Thermo-Calc para determinar a temperatura de estabilidade da fase ferrÃtica e identificar as possÃveis fases intermetÃlicas precipitadas em condiÃÃes de equilÃbrio. As ligas foram envelhecidas a 400 e 475ÂC para estudar a precipitaÃÃo da fase alfa linha (αâ) e seus efeitos nas propriedades mecÃnicas, magnÃticas e de resistÃncia à corrosÃo. Foram realizados tratamentos isotÃrmicos de 600 a 900ÂC para estudar a cinÃtica de precipitaÃÃo das fases intermetÃlicas. As alteraÃÃes microestruturais, nas propriedades mecÃnicas e na resistÃncia à corrosÃo devido a variaÃÃo da composiÃÃo e do tratamento tÃrmico foram estudadas. Os resultados obtidos nas ligas experimentais tratadas a 400 e 475ÂC indicaram aumento na dureza e reduÃÃo da fase ferrita, acompanhada de aumento da suscetibilidade a corrosÃo por pite sendo mais crÃtico a 475ÂC, com melhor desempenho observado para a liga 5Mo4Ni. Para as amostras tratadas de 600 a 900ÂC a liga 7Mo2Ni apresentou a menor quantidade de fases deletÃrias precipitadas e menor suscetibilidade a corrosÃo por pite. Ocorreu precipitaÃÃo de austenita para as ligas contendo 4%Ni tratadas a 800ÂC e 900ÂC. A liga 7Mo4Ni apresentou pior desempenho comparada Ãs outras ligas experimentais em todas as condiÃÃes estudadas.Previous research on experimental ferritic steel with high Mo content showed that Mo increases the resistance to naphthenic corrosion and sulfur complexes. However, Mo content above 5 wt% favored the formation of deleterious phases and reduced the toughness of the steel. To improve the toughness of these alloys and keep the ferrite phase stable, was added Ni, increased Cr content to 25% and maintained high Mo content. These new alloys belong to a family of steels known as superferritic stainless steels. They were originally developed for use in heat exchangers and marine environments. There is a current trend to use these alloys in the oil industry driving the research on the effect of the increase of Mo content on the microstructure of these steels. The kinetics of phase precipitation in experimental compositions (Fe25%Cr 5-7%Mo 2-4%Ni) with addition of Nb and Ti will be investigated for temperatures from 400  C to 900  C for different treatment times. In this first stage, Thermo-Calc software was used to determine the temperature stability of the ferritic phase and to identify possible intermetallic phases precipitated at thermodynamic equibrium. The alloys were aged at 400 and 475ÂC for study the alfa prime phase precipitation and their effects on the mechanical, magnetic and corrosion properties. Isothermal treatments were carried out 600 ÂC to 900  C to study the kinetics of precipitation of intermetallic phases. The microstructural changes on the mechanical and corrosion properties due to variation in composition and heat treatment were studied. The results obtained in the experimental alloys treated at 400 and 475ÂC indicated an increase in hardness, while wt% of ferrite had decreased, accompanied by increased susceptibility to pitting corrosion, the best performance observed for 5Mo4Ni alloy these conditions. For samples treated 600 to 900ÂC the 7Mo2Ni alloy showed the smallest amount deleterious phase precipitated and less susceptibility to pitting corrosion. Austenite phase precipitation occurred for the alloys containing 4%Ni treated at 800ÂC and 900ÂC. The 7Mo4Ni alloy showed worse performance compared to other experimental alloys in all conditions studied.
24
Heise, Martin. "Synthese intermetallischer Phasen mittels mikrowellenunterstütztem Polyol-Prozess." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-183425.
Full textAbstract:
Schon seit dem 17. Jahrhundert ist bekannt, dass kolloidales Gold in wässrigen Lösungen eine rötliche Färbung hervorruft; ein Effekt der direkt aus der Nanostrukturierung des Goldes resultiert. Neben der Modifizierung optischer Eigenschaften können durch Nano- oder Mikrostrukturierung auch andere, neuartige Charakteristika hervorgerufen werden, wie bspw. an Bi3Ni nachgewiesen werden konnte: Mittels mikrowelleninduzierter, reduktiver Umsetzung in Ethylenglykol (mikrowellenunterstützter Polyol-Prozess) konnten submikroskalige Bi3Ni-Stäbchen kristallisiert werden, die in Magnetisierungsmessungen die überaus seltene Koexistenz von Supraleitung und Ferromagnetismus zeigten. Ein Quanteneffekt, der im entsprechenden Volumenmaterial nicht nachgewiesen werden kann und auf spezielle Oberflächenzustände zurückzuführen ist.
Durch Nanostrukturierung können außerdem die chemischen Eigenschaften entscheidend beeinflusst werden, wie an BiRh gezeigt werden konnte. Der mikrowellenunterstützte Polyol-Prozess begünstigt hierbei die Kristallisation von pseudohexagonalen Plättchen mit 60 nm Durchmesser und 20 nm Dicke. Im Gegensatz zum Volumenmaterial zeigten diese in der industrierelevanten Semihydrierung von Acetylen zu Ethylen Bestwerte sowohl in Bezug auf den Umsatz als auch die Selektivität.
Basierend auf diesen Erkenntnissen sollten mithilfe des mikrowellenunterstützten Polyol-Prozesses im Rahmen der vorliegenden Dissertation nanostrukturierte, intermetallische Verbindungen des Typs M–M‘ (M = Sn, Pb, Sb, Bi; M‘ = Fe, Co, Ni, Cu, Pd, Ir, Pt) hergestellt und eingehend chemisch sowie physikalisch charakterisiert werden. Als Edukte dienten Metallsalze, die stets in Ethylenglykol als primäres Lösungs- und Reduktionsmittel umgesetzt wurden. Das Polyol nimmt zusätzlich als oberflächenaktive Substanz Einfluss auf Partikelgröße und -gestalt. Zur Optimierung der Synthesen und um möglichst viele Phasen zugänglich zu machen, wurden Art und Konzentration der Metallsalze, pH-Wert, Reaktionstemperatur und -zeit variiert sowie die Zugabe von Oleylamin und/oder Ölsäure getestet. Oleylamin und Ölsäure sind ihrerseits oberflächenaktive Substanzen, wobei erstere zugleich reduktiv wirken kann. Die methodeninhärente Nanostrukturierung der Produkte führte teilweise zu bemerkenswerten Effekten in der Phasenbildung sowie Beeinflussung der chemischen Eigenschaften.
Nahezu das komplette binäre Phasensystem Bi–Pd konnte durch Optimierung der Syntheseparameter zugänglich gemacht werden. Die Besonderheit hierbei: Neben den Raumtemperaturphasen Bi2Pd, Bi2Pd5 und BiPd3 konnte Bi12Pd31 als Hochtemperaturmodifikation sowie die neue und zugleich metastabile Modifikation gamma-Bi1.0Pd erzeugt und stabilisiert werden. Das im NiAs-Strukturtyp kristallisierende gamma-Bi1.0Pd zeigte in Magnetisierungs- und Widerstandsmessungen Supraleitung unterhalb von 3.2 K.
Mittels mikrowellenunterstütztem Polyol-Prozess gelang bereits in eigenen Vorarbeiten die Synthese von nanostrukturiertem Bi3Ir. Die Verbindung ist ausschließlich in nanopartikulärer Form bei Raumtemperatur empfindlich gegenüber molekularem Sauerstoff und bildet im Zuge einer unkonventionellen oxidativen Interkalation das intermetallische Suboxid Bi3IrOx. Dieses Verhalten ist verknüpft mit einer amorphen Hülle um die Bi3Ir-Nanopartikel, da diese zur Aktivierung des molekularen Sauerstoffs benötigt wird. Unter Einsatz von Reduktionsmitteln — z.B. Wasserstoff, Superhydrid®, Hydrazin — ist der Oxidationsprozess für x < 2 vollständig reversibel. Im Rahmen der vorliegenden Arbeit konnten die Erkenntnisse über Bi3Ir und Bi3IrOx vertieft werden: Bi3IrOx konnte als erster Sauerstoffionenleiter bei Raumtemperatur klassifiziert werden, der darüber hinaus metallisch ist. Dies gelang mittels Röntgen- und Elektronenbeugung, hochauflösender Transmissionselektronenmikroskopie, Röntgenphotoelektronenspektroskopie, quantenchemischen Rechnungen, und Experimenten zur Reaktionskinetik. Mit 84 meV ist die Aktivierungsenergie für die Ionenleitung um eine Größenordnung kleiner als in allen konventionellen Sauerstoffionenleitern. Der Diffusionskoeffizient beträgt für 25 °C 1.2·10–22 m2s–1, was in Anbetracht der 10–19 m2s–1 des Yttrium-stabilisierten Zirkoniumoxids (häufig genutztes Referenzmaterial) bei 150 °C wenig erscheint, aber eben schon für Raumtemperatur gilt.
Durch den mikrowellenunterstützten Polyol-Prozess konnten erstmals phasenreine, nanostrukturierte Proben von PbPd3, Pd20Sb7, Pd8Sb3, PdSb, Ni5Sb2, und Pd13Sn9 synthetisiert werden sowie alternative Syntheserouten für weitere Phasen (alpha-/beta-/gamma-Bi2Pt, BiPt, NiSb, beta-Ni3Sn2, Pd2Sn, PdSn, Pt3Sn, PtSn, PtPb) ermittelt werden, wobei mehrfach die Bildung von Hochtemperaturphasen beobachtet wurde. Weiterhin konnten einige Grenzen der Methode aufgezeigt werden: Während blei- und bismutreiche Phasen prinzipiell einfach kristallisiert werden können, sind antimon- und zinnreiche Verbindungen mit der Methode kaum erreichbar. Außerdem zeigte sich, dass in den meisten Phasensystemen nur bestimmte Verbindungen angesteuert werden können; die Bildung der intermetallischen Phasen ist häufig die Triebkraft zur Reduktion der Metallkationen. In den Systemen von Co-Sb, Co-Sn und Ir-Sb konnte bisher keine Feststoffbildung beobachtet werden.
25
Zhang, Nannan Verfasser], Florian [Akademischer Betreuer] Kargl, and Andreas [Akademischer Betreuer] [Bührig-Polaczek. "Influence of fluid flow and iron intermetallic phases on the microstructure of directionally solidified Al-Si-Cu-Fe alloys / Nannan Zhang ; Florian Kargl, Andreas Bührig-Polaczek." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1192217853/34.
Full text
26
Zhang, Nannan [Verfasser], Florian Akademischer Betreuer] Kargl, and Andreas [Akademischer Betreuer] [Bührig-Polaczek. "Influence of fluid flow and iron intermetallic phases on the microstructure of directionally solidified Al-Si-Cu-Fe alloys / Nannan Zhang ; Florian Kargl, Andreas Bührig-Polaczek." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1192217853/34.
Full text
27
Michailovskaja, Ilona. "Intermetalinio junginio susidarymas sistemoje Ni-W." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080924_184126-35293.
Full textAbstract:
Redukuojant vandeniliu Ni ir W oksidus 1000-1100˚C temperatūrų intervale, nepriklausomai nuo mišinio sudėties, susidaro tik intermetalinis junginys Ni4W. Rentgeno struktūrinės analizės pagalba buvo nustatyta kietafazių reakcijų produktų sudėtis. Nikelio ir volframo oksidų mišiniuose vykstant redukcijai susidarantis nikelis yra volframo oksidų redukcijos katalizatorius. Nikeliui sudarius intermetalinį junginį Ni4W, volframo oksidai redukuojasi sunkiau. Mišiniai, kuriuose Ni:W=4:1, redukuojasi žemesnėje temperatūroje ir esant mažesnei vandenilio dujų koncentracijai.During the reduction of nickel and tungsten in a temperature range from1000- 1100˚C independent of composition mixtures form only Ni4W intermetallic compuond. Their formation was analyzed be of the X-ray diffraction techniques composition the products of the solid-state reactions was determined. Nickel wich is formed during the rediction is catalyst of tungsten oxide. When nickel is formed intermetallic compound Ni4W, tungsten oxide reducible heavily. Reduction of mixture (Ni:W = 4:1) lesses of the temperature and hydrogen concentration.
28
Kaganovskii, Yuri, Lyudmila N. Paritskaya, and Valeriy V. Bogdanov. "Lateral diffusion spreading of two competitive intermetallic phases along free surface (system Cu-Sn): Lateral diffusion spreading of two competitive intermetallicphases along free surface (system Cu-Sn)." Diffusion fundamentals 6 (2007) 43, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14219.
Full text
29
Horák, Karel. "Tepelná a mechanická odolnost zinkového povlaku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228774.
Full textAbstract:
The work is aimed at studying the thermal degradation of the protective zinc coating. Its large part deals with the structure of the various stages of transition and their arrangement, the main emphasis is on analysis of brittle intermetallic phases, which arise due to increased temperature. Conclusion of the work is trying to clear itself causes degradation of this protective layer.
30
Partaix, Axelle. "Contribution à l'étude de quelques transformations de phases dans des alliages à base TiAl." Rouen, 1996. http://www.theses.fr/1996ROUES060.
Full textAbstract:
L'objet de ce travail est d'apporter une meilleure connaissance des caractéristiques microstructurales et chimiques des intermétalliques à base TiAl ainsi que des mécanismes qui gouvernent certaines transformations de phases intervenant dans ces alliages. La première partie de l'étude concerne le rôle de l'oxygène, facteur réputé comme déterminant, sur la ductilité à température ambiante des alliages TiAl. Deux résultats importants ont été établis : i) la localisation préférentielle de l'oxygène dans la phase alpha deux et ii) la solubilité maximale de l'oxygène de l'ordre de trois cents ppm atomiques dans la phase gamma à l'équilibre. L'influence de différents paramètres (stoechiométrie des phases, teneur globale en oxygène, addition d'un troisième élément) sur cette solubilité a été étudiée. L'interprétation de ces résultats en terme d'environnement chimique des sites interstitiels favorables à la localisation de l'oxygène a été proposée. Deux transformations de phases ont été étudiées dans la deuxième partie : la formation de la phase alpha deux dans la structure lamellaire et la transformation massive de alpha en gamma. A partir des résultats expérimentaux, le rôle de l'oxygène est discuté vis-à-vis des mécanismes régissant ces transformations. En particulier, l'oxygène conduit à la présence de fautes dans la phase gamma massive et empêche la transformation massive d'être complète. Dans la dernière partie, le rôle des éléments d'addition et leur répartition entre les phases sont étudies dans un alliage quaternaire biphasé (alpha deux+gamma) contenant du chrome et du niobium. Une interprétation du comportement à la fois gamma-phile et alpha-deux gène du niobium a été donnée à partir de la forme des lobes de solubilité dans les coupes isothermes de diagrammes ternaires.
31
Londoño, Antonio José Ramirez. "Estudo da precipitação de nitreto de cromo e fase sigma por simulação térmica da zona afetada pelo calor na soldagem multipasse de aços inoxidáveis duplex." Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-27072001-165148/.
Full textAbstract:
Os aços inoxidáveis duplex são materiais com um excelente desempenho, devido às suas sobressalentes propriedades mecânicas e excelente resistência à corrosão. Uma composição química adequada e microestrutura balanceada são as responsáveis por esta combinação de propriedades. No entanto, são estes mesmos fatores que os fazem especialmente susceptíveis à precipitação de fases intermetálicas, com efeitos maléficos no seu desempenho. Durante os ciclos térmicos de uma soldagem multipasse, a precipitação de intermetálicos é crítica. Foi desenvolvido um método para simular os ciclos térmicos de uma solda multipasse. Usando este método, foi estudada a precipitação de nitreto de cromo e fase sigma na zona afetada pelo calor submetida a temperaturas abaixo de 950°C dos aços inoxidáveis duplex UNS S31803 e S32550. Foram estudadas energias de soldagem na faixa de 0,4 a 1,0 kJ/mm. Foi determinada mediante extração de precipitados, seguida de difração de raios X na câmara de Debye-Scherrer e microscopia eletrônica de transmissão, a precipitação de nitreto de cromo para energias de soldagem de 0,4 a 1,0 kJ/mm e de fase sigma para energias de soldagem de 0,6-1,0 KJ/mm, no UNS S32550. Já o UNS S31803 não apresentou precipitação alguma para as energias de soldagem estudadas. Baseando-se nos resultados verifica-se que durante uma soldagem multipasse o UNS S31803 é menos propenso que o UNS S32550 à precipitação de intermetálicos na zona afetada pelo calor submetida a temperaturas abaixo de 950°C.Duplex stainless steels belong to a group of high performance stainless steels regarding to corrosion and mechanical properties. These achievements are related to a suitable chemical composition and a balanced microstructure. During welding thermal cycles the microstructure changes and, consequently, corrosion and mechanical properties might be impaired due to a precipitation of intermetallic phases. This precipitation is an issue to be addressed for multipass welding. It was developed a method for simulate the multipass welding thermal cycles. Using this method chromium nitride and sigma phase precipitation was studied in a simulated heat affected zone of multipass welding (three passes) of UNS S31803 and UNS S32550 duplex stainless steels with different heat inputs (0,4 to 1,0 kJ/mm). The HAZ simulated region was below 950°C maximum temperature. Microstructural characterization of simulated samples showed discontinuous films of a precipitated phase at ferrite/ferrite grain boundaries and ferrite/austenite interfaces were observed only in a UNS S32550 duplex grade for all heat inputs simulated. This suggests that sigma phase and chromium nitride precipitation took place during sample thermocycling. X-ray diffraction in a Debye-Scherrer chamber of extracted precipitates and electron diffraction by TEM confirmed the presence of chromium nitrides for all range of heat input studied and sigma phase for heat input above 0,6 kJ/mm. On the other hand, microstructural analysis of UNS S31803 simulated samples did not present precipitation of intermetallic phases in the tested temperature range of HAZ. Based on these results, UNS S31803 is more resistant than UNS S32550 to intermetallic phases precipitation in multipass welding.
32
Lenglet, Manon. "Modèle d'endommagement de fatigue en lien avec la microstructure dans un alliage d'aluminium." Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLM007.
Full textAbstract:
Dans le domaine aéronautique, un défi majeur réside dans l'optimisation du dimensionnement des pièces en tenant compte de leur durée de vie en fatigue. Les phénomènes de fatigue dans les structures métalliques, comme celles du fuselage en aluminium 2139, dépendent de la microstructure. Cependant, comprendre et modéliser ces phénomènes à une échelle aussi fine est coûteux. Jusqu'à présent, l'endommagement des pièces, défini par l'amorçage et la propagation de fissures de fatigue, est pris en compte seulement à l'échelle macroscopique : cela sous-estime la durée de vie des pièces, entraînant un surdimensionnement et des essais coûteux.D'une part, sur le plan expérimental, le comportement mécanique du 2139 sous chargement monotone à l'échelle microscopique et sous chargement cyclique à l'échelle macroscopique est bien compris. Cependant, le comportement de cet alliage sous chargement cyclique et à l'échelle microscopique n'est pas documenté. D'autre part, de nombreuses méthodes numériques ont été développées pour prédire l'amorçage de fissures de fatigue. Les Fatigue Indicator Parameters (FIPs) offrent une approche économique et facile à implémenter, mais il n'y a pas de consensus sur le FIP le plus pertinent. De plus, bien que des méthodes existent pour modéliser la propagation de fissures dans les polycristaux, il n'y a pas de méthode unique utilisant les FIPs pour modéliser à la fois l'amorçage et la propagation de fissures.Ainsi, cette thèse vise à développer une méthode pour modéliser l'amorçage et la propagation de fissures de fatigue à l'échelle de la microstructure. Pour appliquer cette méthode au cas du 2139, divers outils ont été utilisés, notamment des simulations par éléments finis avec Z-set. Le zoom structural a permis de modéliser les phases intermétalliques, sites d'amorçage des fissures de fatigue, et le module de remaillage adaptatif Z-cracks a été employé pour modéliser l'amorçage et la propagation de fissures dans l'alliage. Une campagne expérimentale a également permis de caractériser le comportement cyclique de l'alliage pour les simulations, et grâce à la microscopie optique et électronique il a été possible de suivre l'amorçage et la propagation de fissures en surface à l'échelle de quelques micronsIn the aeronautical field, a major challenge lies in optimizing the sizing of components, taking into account their fatigue life. Fatigue phenomena in metallic structures, such as those in the aluminum 2139 fuselage, depend on microstructure. However, understanding and modeling these phenomena at such a fine scale are expenseive. So far, fatigue damage, defined by the initiation and propagation of fatigue cracks, is only considered at the macroscopic scale: this underestimates the life of components, leading to oversizing and expensive testings.On one hand, experimentally, the mechanical behavior of 2139 under monotonic loading at the microscopic scale and cyclic loading at the macroscopic scale is well understood. However, the behavior of this alloy under both cyclic loading and at the microscopic scale is not documented. On the other hand, numerous numerical methods have been developed to predict the initiation of fatigue cracks. Fatigue Indicator Parameters (FIPs) offer an economical and easy-to-implement approach, but there is no consensus on the most relevant FIP. Moreover, although methods exist to model crack propagation in polycrystals, there is no single method using FIPs to model both crack initiation and propagation.Thus, this thesis aims to develop a method to model the initiation and propagation of fatigue cracks at the microstructure scale. To apply this method to the case of 2139, various tools have been used, including finite element simulations with Z-set. The structural zoom has been used to model intermetallic phases, sites of crack initiation, and the adaptive remeshing module Z-cracks has been employed to model crack initiation and propagation in the alloy. An experimental campaign has also characterized the cyclic behavior of the alloy for simulations, and with optical and electron microscopy, it has been possible to track crack initiation and propagation on the surface at the scale of a few microns
33
Kientz, Marie-Odile. "Caractérisation de solutions solides nanocristallines Fe-X (X=Sn, Sb) élaborées par mécanosynthèse : transformations de phases induites par broyage dans des composés intermétalliques." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL088N.
Full textAbstract:
Les nanomatériaux, matériaux de structure nanocristalline, suscitent depuis quelques années un vif intérêt: leur forte densité d'interfaces leur confère des propriétés physico-chimiques originales. L’élaboration de ces matériaux nanocristallins peut se faire par différentes méthodes, dont la mécanosynthèse. L’étude de solutions solides nanocristallines vise à obtenir une meilleure connaissance des nanomatériaux, avec notamment la caractérisation des joints de grains. Quant à la seconde étude, elle porte sur la caractérisation du désordre induit par broyage. Le choix de systèmes et composés à base de fer est sous-tendu par le fait que nous utilisons comme technique principale d'analyse la spectrométrie Mössbauer (57Fe, 119Sn, 121Sb), particulièrement bien adaptée à ces études puisqu'elle est sensible aux phénomènes qui se passent à l'échelle du nanomètre. La synthèse des solutions solides nanocristallines est réalisée à partir d'un mélange de poudres de fer et d'étain (ou antimoine) par broyage à haute énergie dans des conditions expérimentales bien définies. Après une caractérisation de ces solutions solides (composition chimique, taille des grains), le travail primordial porte sur l'étude des joints de grains dans de tels matériaux: structure, largeur des joints de grains, propriétés magnétiques, évolution lors de traitements thermiques. Toutes ces informations conduisent à conclure à une structure peu désordonnée de ces joints de grains. Confrontées à d'autres résultats concernant des matériaux nanocristallins obtenus par des techniques différentes, il apparait que la nature des joints de grains est fortement dépendante du mode d'élaboration. L’étude du désordre induit par broyage est menée dans des composés intermétalliques ordonnes de type L12 et dans des stannures de fer. Nous suivons l'évolution de ces composés intermétalliques au cours du broyage et caractérisons l'équilibre dynamique atteint par les poudres dans des conditions de broyage données
34
Febri, Maria Immaculata Maya. "Synthèse de poudres d'alliages intermétalliques terres rares-métaux 3D et de leurs phases d'insertion par des procédés chimiques à basse température : obtention de nanocomposites à haute perméabilité magnétique par réaction-décomposition controlée de ces phases d'insertion." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10223.
Full textAbstract:
Les methodes conventionnelles de synthese d'alliages intermetalliques contenant terres rares (tr) et metaux 3d (m) s'effectuent par fusion des metaux precurseurs. L'impossibilite d'obtenir directement apres fusion (c. -a-d. Sans post-recuit d'homogeneisation) des alliages a fusion non congruente limite cette approche. L'approche chimique par calciothermie, appelee procede d'oxyde-reduction-diffusion (ord) presentee ici, permet d'operer a plus basses temperatures, par consequent d'obtenir des alliages stables, en dessous de leur point de fusion non congruent ; le post-recuit devient alors inexistant. Dans ce procede, l'oxyde de terre rare et du metal (m) (precurseurs en poudre) sont melanges puis chauffes en presence de calcium en leger exces. A l'etat liquide, ce dernier joue un double role d'agent reducteur (reduction oxyde de terre rare en metal) et de milieu reactionnel, afin de faciliter la diffusion des especes metalliques reactantes. Des alliages binaires et ternaires repondant a des formules diverses ont ainsi ete synthetises. Ce travail montre que le procede ord est devenu une bonne alternative d'elaboration d'alliages tr-m. L'apport de la chimie est ensuite etendu aux procedes d'hydruration et de nitruration des alliages tr-m, ou l'hydrogene (ou l'azote) est libere par la decomposition des composes sources: nah ou nabh#4 en presence d'eau, et nan#3. Les reactions d'hydruration (de nitruration) chimiques sont caracterisees par des mesures magnetiques (aimantation, t#c, h#c,). On montre que la voie chimique permet d'abaisser les temperatures operatoires d'hydruration (de nitruration). Enfin, en controlant la reaction de segregation des phases d'insertion metastables (hydrures, nitrures) d'alliages tr-m, on parvient a obtenir des nanocomposites. Par exemple, la segregation des alliages ternaires nd-(fe,co)-b avec l'azote (>400c) forme des nanocomposites constitues des precipites de ndn (refractaires) dans une matrice nanocristalline d'alliage fe-co. Ceux-ci presentent en plus une susceptibilite magnetique elevee dans la gamme de frequences 0,1-20 ghz. Ils constituent ainsi une nouvelle classe d'absorbants de micro-ondes
35
Chaumat, Valérie. "Equilibres de phases et microstructures d'alliages Nb-Ti-Al élaborés par mécanosynthèse." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0073.
Full textAbstract:
L'amelioration des performances des moteurs aeronautiques et de certains dispositifs nucleaires necessite l'augmentation des temperatures de fonctionnement des pieces chaudes en contact avec des milieux dont la temperature peut varier de 900 a 1600c. C'est dans ce contexte que sont etudies les alliages a base de niobium du systeme nb-ti-al. Dans ce systeme, ce travail a cherche a approfondir la connaissance des equilibres de phases, dont dependent les proprietes, ainsi que l'interet technique de l'elaboration par broyage de poudres (mecanosynthese). Deux approches, l'une theorique par la methode variationnelle des amas, l'autre experimentale par diffraction de neutrons, ont permis de determiner les limites en temperature et en composition du domaine d'existence de la phase ordonnee de structure cubique centree b2 dans le systeme nb-ti-al. Il apparait ainsi que ce domaine est particulierement etendu vers les teneurs riches en niobium. Nous avons egalement constate que la temperature de transition ordre - desordre b2 a2 et le degre d'ordre sont tres sensibles aux variations de composition. Par ailleurs, nous avons montre la possibilite d'elaborer par mecanosynthese a partir des elements constitutifs nb, ti, al des alliages a base de niobium du type nb-ti-al repondant aux specifications de purete et d'homogeneite de composition. Une attention particuliere est portee a l'analyse des mecanismes de transformation de phases au cours du broyage et de la densification
36
Guillaume, Alexandre. "Transitions de phases dans les fermions lourds sous contrainte uniaxiale." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10060.
Full textAbstract:
Nous presentons les premiers resultats obtenus avec un dispositif experimental permettant de changer la contrainte uniaxiale continument a tres basse temperature. Le principe de l'appareil consiste a controler la pression d'helium appliquee sur un soufflet metallique connecte thermiquement a la boite de melange d'un refrigerateur a dilution. Nous etudions l'effet de la contrainte uniaxiale, appliquee selon l'axe c du compose tetragonal uru#2si#2. Nous trouvons que la temperature de transition supraconductrice t#c varie de facon parabolique en fonction de la contrainte #c avec une pente de 76 mk/kbar a #c = 0 kbar et une pente nulle a 6. 5 kbar. La temperature de transition antiferromagnetique t#n varie lineairement en fonction de la contrainte avec une pente egale a 32 mk/kbar. Nous rapportons les premieres mesures de l'evolution du gap des excitations de la phase antiferromagnetique en fonction de la contrainte uniaxiale selon l'axe c. Il decroit lineairement avec une pente de 0. 63 k/kbar. Grace aux mesures de champ critique, nous donnons la premiere estimation de la croissance de la masse effective avec la contrainte selon l'axe c, m*(6. 5 kbar) = 1. 07 m*(0 kbar). Pour le compose hexagonal upt#3, nous confirmons que la temperature de transition supraconductrice t#+#c decroit, d'abord avec une pente de 14. 71. 5 mk/kbar, pour une contrainte appliquee suivant l'axe c inferieure a 2 kbar puis decroit, avec une pente de 5. 20. 7 mk/kbar, pour des contraintes superieures. En variant de 0 a 8. 4 kbar la contrainte #a appliquee selon l'axe a, nous trouvons que la temperature t#+#c decroit regulierement avec une pente de 2. 00. 7 mk/kbar. A partir de l'evaluation du coefficient a de la loi = #0+at#2 et de la pente du second champ critique a bas champ, nous trouvons que la masse effective augmente avec la contrainte suivant l'axe c et diminue avec la contrainte suivant l'axe a:m*(#c = 6. 5 kbar) = 1. 26 m*(#c = 0 kbar) ; m*(#a = 6. 5 kbar) = 0. 86 m*(#a = 0 kbar).
37
Král, Michael. "Struktura a vlastnosti svarového spoje TiAl6V4/6061 zhotoveného technologií elektronového paprsku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318832.
Full textAbstract:
Titanium and aluminium alloys are among the most used construct materials due to their physical and mechanical properties except steels. The joining of these alloys can improve properties of whole construction but it is still difficult task. Especially welding of titanium and aluminium alloys is difficult cause formation of undesirable intermetalic phases in the weld. This thesis focuses on influences of electron beam welding parameters especially focusing and deflection of beam and preheating of base material to quality of heterogeneous join of titanium alloy Ti6Al4V and aluminium alloy EN AW-6061 – T651. There is described preparation of welded joins and brazed joins in the thesis, which are evaluated by light microscopy, scanning electron microscopy and EDS analysis of chemical composition. There was evaluated presence and chemical composition of formated intermetalic phases in the welded joins and quality and defects in the brazed joins.
38
Stegmaier, Saskia [Verfasser], Thomas F. [Akademischer Betreuer] Fässler, Hubert [Akademischer Betreuer] Schmidbaur, and Karsten [Akademischer Betreuer] Reuter. "Clusters and Networks of Tetrel Elements and Late d Block Metals in Ternary Intermetallic Phases with Alkali and Alkaline Earth Metals / Saskia Stegmaier. Gutachter: Thomas F. Fässler ; Hubert Schmidbaur ; Karsten Reuter. Betreuer: Thomas F. Fässler." München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1051935032/34.
Full text
39
Berthold, Rico. "Strukturell komplexe intermetallische Verbindungen im System Al-Mg-Zn." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-155096.
Full textAbstract:
Die Elemente Al, Mg und Zn sind wichtige Komponenten für leichte und hochfeste Legierungen, wie die Al- oder Mg-Knetlegierungen. Darüber hinaus ist das Al-Mg-Zn-System sehr interessant, weil vier ternäre komplexe intermetallische Phasen, genannt τ1, τ2, Φ und q, darin vorkommen. Die aktuellen experimentellen Phasendiagramme des Al-Mg-Zn-Systems enthalten nur provisorische oder keine Homogenitätsbereiche der Φ-, τ2- und der q-Phase aufgrund unzureichender experimenteller Daten. Ziel der Arbeiten war es, die Homogenitätsbereiche der q-, τ2- und der Φ-Phase neu zu ermitteln und die Kristallstruktur der Φ-Phase zu bestimmen. Proben wurden durch Schmelzen und Wärmebehandlung in Ta-Ampullen oder durch Zentrifugieren aus der Schmelze hergestellt und durch XRD, SEM, EDXS, WDXS und DSC charakterisiert. Während der Neuuntersuchung der Al-Mg-Zn Phasengleichgewichte in der Nähe des Teilsystems Mg-Zn und nahe bei τ1 wurde eine Reihe von neuen ternären Phasen entdeckt. Die Kristallstrukturen für die Φ-Phase (Pbcm, a = 8,9374 (2) Å, b = 16,812 (3) Å, c = 19,586 (4) a) und drei der neuen intermetallischen Verbindungen wurden gelöst und die Kristallstruktur des τ2 Phase wurde erneut untersucht. Während τ2 (Pa-3, a = 23,034 (3) Å) ein Approximant der ikosaedrischen quasikristallinen Phase q ist, erwies sich eine der neuen Phasen (τd, Imm2, a = 5,2546 (2), b = 40,240 (2), c = 25,669 (1) Å) als dekagonaler Approximant. Überraschenderweise wurde eine Phase (Fd-3m, a = 27,5937 (9) Å) gefunden, die isotyp zu der binären Phase β-Al3Mg2 ist, aber eine Zn-reiche Zusammensetzung hatThe elements Al, Mg and Zn are major components for a large number of light and high strength alloys, such as the Al-based alloys of the 7xxx series. In addition, the Al-Mg-Zn system has attracted much interest because four complex metallic alloy phases, called τ1, τ2, Φ and q are formed as ternary intermetallic compounds. The current experimental phase diagrams of the Al-Mg-Zn system contain only provisional or no homogeneity ranges of the Φ phase, τ2 phase and the q phase due to insufficient experimental data. The aim of the work was to redetermine the homogeneity ranges of the q, τ2 and the Φ phases and to determine the crystal structure of the Φ phase for a reliable data set. Samples were prepared by furnace-controlled melting and annealing in Ta ampoules or by centrifugation from the self-flux and characterized by XRD, SEM, EDXS, WDXS and DSC. While reinvestigating the Al-Mg-Zn phase equilibria in the vicinity of the subsystem Mg-Zn close to τ1, a number of new ternary phases were discovered. Single phase material could be obtained for the known Φ and τ2 phases and for four new intermetallic compounds. The crystal structures for the Φ phase and two of the new intermetallic compounds were solved and the crystal structure of the τ2 phase was reinvestigated. While τ2 (Pa-3, a = 23.034(3) Å) is an approximant of the icosahedral quasicrystalline phase q, the Φ phase (Pbcm, a = 8.9374(2) Å, b = 16.812(3) Å, c = 19.586(4) Å) and one of the new phases (Imm2, a = 5.2546(2), b = 40.240(2), c = 25.669(1) Å) turned out to be decagonal approximants. Surprisingly, we have found one phase (Fd-3m, a = 27.5937 (9) Å) isotypic to the Samson’s phase β-Al3Mg2 at Zn rich composition
40
Wolski, Krzysztof. "Influence de la dispersion de phases céramiques sur la résistance au fluage de l'intermétallique FeAl." Grenoble INPG, 1994. http://www.theses.fr/1994INPG4207.
Full textAbstract:
L'objectif du present travail etait d'ameliorer la resistance au fluage de l'intermetallique feal par dispersion d'une phase ceramique. Les materiaux ont ete prepares par mecanosynthese ou par attrition, toutes deux couplees a l'oxydation in situ et suivies du frittage sous charge. Les phenomenes physico-chimiques, intervenant au cours de l'elaboration, ont ete analyses: la formation complete de feal par mecanosynthese a ete demontree (atd, drx, mossbauer), l'utilisation du lubrifiant (acide stearique) conduit a la formation du carbure fragilisant fe#3alc#0#,#7, ce carbure a ete transforme en zrc par l'ajout de zrh#2 ou elimine par suppression du lubrifiant, la dispersion formee par oxydation in situ est plus efficace que l'ajout de poudres ceramiques, les produits d'oxydation sont transformes au cours du frittage (t#f<1150c) en spinelle feal#2o#4, l'augmentation de t#f conduit a la transformation du spinelle en -al#2o#3, qui coalesce par la suite. L'optimisation des cycles de broyage et de frittage (oxydation in situ, suppression du lubrifiant et diminution de t#f) a permis d'elaborer des composites feal-feal#2o#4, ou le spinelle (5 a 15 vol%) est present sous forme d'une dispersion nanometrique (10 a 50 nm). Les proprietes rheologiques des composites feal-feal#2o#4, ont ete analysees par des essais de compression a vitesse de deformation imposee (3. 10#-#6 - 3. 10#-#4s#-#1) a 727c, et decrites a l'aide d'une loi puissance sans contrainte seuil d/dt=a#n. La contrainte d'ecoulement (=350 mpa) et le coefficient de sensibilite a la contrainte (n=13) sont triples par rapport au feal non renforce (=105 mpa, n=4), ce qui procure a ces composites un excellent comportement au fluage. Cette amelioration est essentiellement due a la dispersion nanometrique du spinelle, dont la stabilite a ete analysee du point de vue de la cinetique de coalescence et verifiee experimentalement
41
Amri, Noureddine. "Etude métallurgique des systèmes Fe-Nd, Fe-Dy et Fe-Nd-Dy : existence et stabilité de phases." Rouen, 1993. http://www.theses.fr/1993ROUES041.
Full textAbstract:
La formation de la phase métastable A1 dans les alliages Fe-Nd solidifiés de différentes façons est étudiée. Sa composition chimique estimée grâce à la microsonde électronique est très riche en fer (65 à 70% at. Fer). Son domaine d'existence, sa fraction volumique ainsi que sa cinétique de transformation en Nd2Fe1#7, sont fortement liés à la vitesse de solidification et à la composition de l'alliage. La substitution de l'Al au Fe dans la phase Nd5Fe1#7 se fait d'une manière indirecte à travers la réaction péritectoïde de la phase Nd2Fe1#7 (avec l'aluminium en substitution au fer). La phase nommée a#2 (Nd5Fe1#7 avec Al en substitution) est totalement différente de la phase (phase stable dans le ternaire Fe-Nd-Al). L'influence de la substitution de l'Al dans les phases A1 et Nd2Fe1#7 est également étudiée. Dans l'alliage ternaire Fe-Nd-Dy, la phase A1 est complètement supprimée. La phase Nd5Fe1#7 accepte du dysprosium en substitution au Nd mais en faible quantité, car au-delà d'un certain taux de Dy dans la phase, elle est déstabilisée au bénéfice de la phase de laves pseudo-binaire Fe2 (Nd, Gy) parfaitement stable
42
Santos, Jorge. "Al-7Si-Mg semi-solid castings – microstructure and mechanical properties." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-38693.
Full textAbstract:
The vehicles industry is facing increasing demands for fuel efficiency and cost reduction due to environmental legislation, sustainability and customer demands. Therefore, there is a great need to develop and produce lightweight components by using materials and processes that offer higher specific strength and/or design optimization. Semi‐solid aluminium casting offers design freedom and castings with lower shrinkage and gas entrapment defects compared to high pressure die castings. The lack of understanding of microstructure and defect formation, and design data, for semi‐solid castings is a barrier for foundries and designers in the vehicles industry to use semi‐solid castings. In this study, the effect of two grain refiners on slurry formation and surface segregation of semi‐solid Al‐7Si‐0.3Mg castings produced by the Rheometal™ process was evaluated. The influence of grain refinement on primary α‐Al grain size, shape factor and solid fraction was analysed in addition to the solute content of the surface segregation layer. The influence of magnesium on the formation of intermetallic phases during solidification and the heat treatment response of Al‐7Si‐Mg semi‐solid castings was investigated. The magnesium content was varied from 0.3 to 0.6wt.% and the semi-solid castings were analysed in the T5 and T6 conditions. Energy dispersive spectroscopy was used to identify the intermetallic phases formed during solidification. Tensile testing was performed and the results were correlated to the magnesium and silicon concentration measured in the interior of the α‐Al globules formed during slurry preparation. The results suggest that the addition of grain refiner decreases the solid fraction obtained in the Rheometal™ process. However, no significant effect was observed on the α‐Al grain size and shape factor. A good correlation was obtained between the magnesium concentration in the interior of the α‐Al globules formed during slurry preparation and the offset yield strength for all alloys. The low magnesium solubility in α‐Al at temperatures in the solidification range of the Al‐7Si‐Mg alloys is suggested to be the reason for the low hardening response for the T5 heat treatment compared to the T6 condition.
43
Kaiser, Martin. "Metastabile intermetallische Phasen durch Niedertemperaturtransformationen von Subhalogeniden." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-156800.
Full textAbstract:
Maßgeschneiderte Eigenschaften von Funktionsmaterialien sind ein fundamentaler Aspekt für die Technologien unserer Gesellschaft und deren Weiterentwicklung. In diesem Zusammenhang bilden die Modifizierung bestehender Synthesestrategien und die Entwicklung neuartiger Synthesewege die grundlegende Voraussetzung für Innovation. Der Zugang zu den benötigten Materialien wird in den bis dato angewandten Synthesemethoden häufig durch die thermodynamische Stabilität einer Verbindung begrenzt.
Zielstellung der vorliegenden Arbeit ist es, eine Strategie zur postsynthetischen Umwandlung und Modifizierung bereits vorhandener komplex strukturierter Feststoffe anzuwenden, durch die es gelingt, Zugang zu weiteren Materialien zu erhalten. Als Feststoffprekursoren wurden hierfür verschiedene ternäre und quaternäre, bismutreiche Subhalogenide gewählt, die bei niedrigen Temperaturen bis 70 °C mit dem Reduktionsmittel n-Butyllithium (nBuLi) zur Reaktion gebracht wurden, um diese in topochemischen Reaktionen zu neuen intermetallischen Phasen umzuwandeln.
Die Bismutsubiodide Bi12Ni4I3, Bi8Ni8SI2 und Bi28Ni25I5 enthalten intermetallische Stäbe, deren Querschnitte nur vier bis elf Atome umfassen, was effektiven Durchmessern von ca. 0,8 bis 1,2 nm entspricht. Zudem befinden sich Iodidionen in den Kristallstrukturen, die die metallischen Stäbe voneinander separieren. Die reduktiven Behandlungen dieser Feststoffprekursoren führten jeweils zur quantitativen Deinterkalation der Iodidionen und dadurch zur Zusammenlagerung der metallischen Stäbe zu kompakten Stabpackungen. In Pseudomorphosen wurden zum einen Kristalle erhalten, die eine Vielzahl parallel angeordneter Bi3Ni-Faserbündel enthielten, zum anderen bildeten sich die bisher unbekannten, kristallinen Phasen Bi8Ni8S und Bi28Ni25.
Während bei den Umwandlungen die strukturellen Charakteristiken der intermetallischen Teilstrukturen der Bismutsubiodide auf die reduzierten Phasen übertragen werden, ändern sich die elektronischen Situationen mit der Variation der Elektronenzahl. Dies lässt sich besonders gut am Beispiel der Umwandlung des Bismutsubiodids Bi28Ni25I5 in die reduzierte Phase Bi28Ni25 verdeutlichen.
Die elektronische Struktur ändert sich durch die Reduktion kaum, sodass die zusätzlichen Elektronen im intermetallischen Teil antibindende Zustände füllen. Das intermetallische Bindungssystem verhält sich dabei wie ein strukturell rigides Elektronenreservoir und toleriert die Änderung der Elektronenzahl bei der topochemischen Umwandlung zu Bi28Ni25. Mit der elektronisch ungünstigen Situation geht die Metastabilität der reduzierten intermetallischen Phase einher.
Die reduktive Behandlung des Bismutsubiodids Bi13Pt3I7 führte nicht nur zur selektiven topochemischen Deinterkalation von Iodidionen sondern zusätzlich zum Ausbau von Bismutatomen, wodurch die in Bi13Pt3I7 vorhandenen Iodidobismutatschichten in Iodidschichten umgewandelt werden. Die intermetallischen Schichten der Ausgangsverbindung bleiben erhalten und nähern sich an, sodass das bis dato unbekannte Bismutsubiodid Bi12Pt3I5 resultiert. Das topotaktische Fortbestehen der intermetallischen Schichten zeigt sich dabei an intermediär gebildeten Kompositkristallen aus Mutter- und Tochterverbindung.
Durch den Abbau der isolierenden Iodidobismutat¬schichten erfolgen die elektronische Kopplung der intermetallischen Schichten und der Übergang des zwei-dimensionalen Metalls Bi13Pt3I7 in das dreidimensionale Metall Bi12Pt3I5. Die topochemische Reaktion wird durch eine Reaktionstemperatur von 45 °C limitiert: Bei erhöhter Reaktionstemperatur bis 70 °C tritt eine Umstrukturierung unter weiterem Iod- und Bismutausbau auf, und die metastabile, binäre Phase Bi2Pt(hP9) wird aufgebaut.
Die dichte Kristallstruktur des erstmals dargestellten Bismutsubchlorids Bi12Rh3Cl2 baut sich aus einem intermetallischen [Bi4Rh]-Netzwerk auf, in dessen Kanäle Chloridionen eingeschlossen sind. Im Zuge der Niedertemperaturreaktion mit nBuLi erfolgt ein unerwarteter quantitativer Austausch der Chloridionen gegen Bismutatome, der die Kristalle des Subchlorids in Kristalle der binären Verbindung Bi14Rh3 überführt. Die kristallchemische Analyse zeigte, dass den [RhBi8/2]-Antiprismen des [Bi4Rh]-Netzwerks die Funktion von Scharnieren zukommt, welche eine Aufweitung des intermetallischen Netzwerks ermöglichen.
So entstehen breite Diffusionspfade, und es resultiert ein dreidimensionales Transportsystem für den enormen Massetransport durch den Kristall. Bei der Austauschreaktion werden die zuvor unabhängig voneinander leitenden intermetallischen Stränge kantenverknüpfter [RhBi8/2]-Würfel elektrisch kontaktiert. Die physikalischen Eigenschaften ändern sich dabei maßgeblich: Aus dem eingeschränkten Metall Bi12Rh3Cl2 entsteht der metastabile Supraleiter Bi14Rh3.
Mit zunehmender Kenntnis über die Strategien zur postsynthetischen Umwandlung und Modifizierung komplexer Strukturen können diese grundsätzlich dazu beitragen, Materialien mit technologisch relevanten Eigenschaften darzustellen.
Insbesondere Phasen, die nur bei hohen Temperaturen thermodynamische Stabilität erlangen oder sogar unter allen Bedingungen metastabil vorliegen, werden durch die geschickte Wahl der Synthesestrategie zugänglich. Möglicherweise werden mit dem wachsenden Wissen zu neuartigen Synthesestrategien die chemischen und physikalischen Eigenschaften eines Materials auf diesem Weg gezielt veränderbar. Insbesondere die herausragenden Stabilitäten der nanoskaligen, intermetallischen Stäbe werfen zudem die Frage auf, ob diese durch die Reaktion mit oberflächenaktiven Reagenzien vereinzelt werden können, um neuartige nanoskalige Leiter herzustellen.
44
Alexander, D. T. L. "Intermetallic phase transformations in 3XXX aluminium alloys." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595425.
Full textAbstract:
There is interest in modelling the industrially important intermetallic phase transformation of Al6(Fe,Mn) to a-Al-(Fe,Mn)-Si that occurs during homogenisation of direct-chill cast ingots of 3XXX aluminium alloy. The kinetics of this "6-to-a" transformation are studied to aid the modelling. The initial investigation uses an Al-0.5Fe-1.0Mn-0.2Si (wt.%) alloy. The morphology of the transformation and the associated local composition changes are studied using a range of electron optical techniques, including energy-filtered transmission electron microscopy (TEM), convergent-beam electron diffraction and field-emission-gun scanning electron microscopy. The transformation proceeds by eutectoid decomposition of the Al6(Fe,Mn) phase into a-phase and aluminium solid solution. The transformation requires intake of silicon from the surrounding matrix, which we believe is supplied along the migrating transformation front. This gives a eutectoid growth rate that is comparatively fast; hence nucleation is found to be the key rate-controlling factor. Intake of manganese is not required for transformation, but does occur on continued annealing. The morphology of transformed particles is not static: eutectoid aluminium coalesces and ripens into "Al-spots", and wetting of Al6(Fe,Mn)/a-phase interfaces by the matrix may ultimately lead to fragmentation of two-phase particles. Roll-bonded diffusion couples permit the study of 6-to-a nucleation by steadily increasing the silicon content in an Al-Fe-Mn alloy (initially containing only Al6(Fe,Mn) particles). Nucleation is found to be sporadic. Results also indicate that the transformation preferentially nucleates at boundaries in the matrix - this is confirmed by TEM studies. If there is insufficient eutectoid nucleation, transformation is by the dissolution of Al6(Fe,Mn) supplying solute for the growth of a-phase. However, preliminary diffusion studies using silicon-coated alloy blocks indicate that a typical ingot microstructure gives sufficient 6-to-a nucleation for the alloy to achieve equilibrium levels of a-phase eutectoidally.
45
Liu, Zhongyi. "Phase transformations in the intermetallic compound ZrCu." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246733.
Full text
46
Meredith, Michael William. "Intermetallic phase selection in dilute aluminium alloys." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624389.
Full text
47
Havlík, Petr. "Svařování heterogenních svarových spojů Ti/Al slitin pomocí elektronového svazku." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-412926.
Full textAbstract:
The problematics of weldability of heterogeneous welds of aluminium and titanium alloys produced by electron beam welding is discussed in this work. Homogenous welds of selected alloys were analyzed in the first stage. Welding of these materials relates to formation of intermetallic phases at the interface of base materials due to differences in physical, chemical and metallurgical properties of base materials. One of the prerequisites for producing high quality weld joints is to find optimal process parameters. The influence of selected process parameters to integrity, structure and mechanical properties of heterogeneous Al/Ti joints is evaluated.
48
Ngakane, M. "Abrasive wear resistance of ruthenium aluminide intermetallic and ferritic steels containing a sigma intermetallic phase." Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/9696.
Full textAbstract:
Bibliography: leaves 106-113.The abrasive wear resistance of ruthenium aluminide intermetallic and ferritic steel containing an iron-chrome sigma intermetallic phase have been investigated in this study. A medium carbon wear resistant steel (MCV) was used in the study to facilitate comparison between wear resistances in the materials of interest. Specimens of ruthenium aluminide, MCV and ferritic stainless steels containing a sigma phase were produced. The MCV steel was quenched and tempered to match the bulk hardness of the as-received ruthenium aluminide. Five different grades of thermomechanically worked ferritic steels specimens were heat treated to produce different volume fractions of sigma phase. The mechanical properties of the specimens were investigated by compression testing and microhardness measurements. Abrasion testing was carried out on a pin on belt abrasion apparatus. The surface response of the specimens to abrasive wear was characterised by optical and scanning electron microscopy. Microhardness of the specimens were measured with a digital microhardness machine. The wear resistance of ruthenium aluminide was found to be higher than all materials tested in this project. The wear resistance in some of the ferritic steels containing sigma phase was comparable to that of the wear resistant medium carbon steel. The surfaces of the specimens were shown to work-harden during the abrasion process. The corresponding work-hardening results showed that ruthenium aluminide had the highest work-hardening rate. It can be concluded that the work-hardening ability of the test materials correlates with their respective wear resistance properties.
49
Nouri, Kamal. "Contribution à l'étude des diagrammes des phases ternaires R-Fe-X (R : Y, Sm; X : Ni, Ga) : Elaborations, études structurales, magnétiques et magnétocaloriques des composés intermétalliques dans les systèmes (Sm,Y)-Fe-(Ni,Ga)." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1139.
Full textAbstract:
Depuis quelques dizaines d’années, l’étude de composés intermétalliques à base des métaux de transition 3d, et d’éléments de terres rares 4f, présente un vif intérêt tant d’un point de vue fondamental qu’appliqué. Les propriétés remarquables de ces matériaux magnétiques proviennent de la présence, dans le même composé, de métaux de transition 3d, caractérisés par un magnétisme itinérant donné par les électrons de la bande externe 3d, et de métaux de terres-rares 4f qui, eux, présentent un magnétisme localisé dû aux électrons de la couche interne 4f. La recherche présentée ici se concentrera sur deux diagrammes des phases ternaires alliant samarium, fer et nickel et l’yttrium, fer et Gallium dans le deuxième système. Ces types d’intermétalliques sont aussi potentiellement caractérisés par un effet magnétocalorique (EMC) défini par le réchauffement ou le refroidissement de ces matériaux magnétiques sous l’application ou la suppression d’un champ magnétique extérieur.Le but de la thèse est la construction des deux diagrammes ternaires qui n’ont jamais été publiés et étudier les propriétés physicochimiques dans les systèmes (Sm,Y)-Fe-(Ni,Ga). Cette recherche aboutira à la détermination des diagrammes ternaires Sm-Fe-Ni et Y-Fe-Ga expérimentales (section isotherme à 800°C) et d’étudier les propriétés structurales de ces composés intermétalliques. Les propriétés magnétiques et magnétocaloriques ont également été étudiées en couplant les analyses magnétiques avec les mesures par diffraction des rayons X et par spectroscopie Mössbauer. Ces travaux ont mis en évidence l’influence importante de la nature et du taux de fer substitué au nickel et au gallium dans les deux systèmes sur les propriétés magnétiquesIn recent decades, the study of intermetallic compounds containing 3d transition metals and 4f rare earth elements presents great interest both from a fundamental point of view and in its various applications. The remarkable properties of these magnetic materials come from the presence, in the same compound, of 3d transition metal, characterized by an itinerant magnetism given by the electrons in the 3d external band, and 4f rare-earth which themselves have a localized magnetism due to the electrons of the 4f inner layer. The research presented here will focus on the construction of two ternary phase diagrams combining [Sm-Fe-Ni] in the first system and [Y-Fe-Ga] in the second one. These types of intermetallics are also characterized by a magnetocaloric effect (EMC) defined by the heating or cooling of these magnetic materials under the application or removal of an external magnetic field.The aims of the thesis are the construction of two ternary phase diagrams that have never been published before and the study of the physicochemical properties in the (Sm, Y) -Fe- (Ni, Ga) systems. This research will lead to the determination of experimental ternary phase diagrams Sm-Fe-Ni and Y-Fe-Ga (isothermal section at 800°C) and to study the structural properties of some intermetallic compounds.The magnetic and magnetocaloric properties were also studied by coupling magnetic analysis with the X-ray diffraction and Mössbauer spectroscopy measurements. This work has highlighted the important influence of the nature and rate of iron substituted by nickel and gallium in both systems on the magnetic properties
50
Temizel, Guvenc. "Intermetallic Phase Formation At Fe-al Film Interefaces." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607589/index.pdf.
Full textAbstract:
This thesis presents the formation mechanism of intermetallics formed at Fe-Al film interfaces. Al thin films with different initial film thicknesses were coated on low carbon steel substrates by physical vapor deposition (PVD). By annealing the system at different temperatures and for different time intervals, several intermetallic phases were observed. X-Ray, SEM and EDS studies showed that intermetallic phases FeAl2 and Fe2Al5 are most dominant phases which were observed and they formed sequentially on the contrary of intermetallics which formed synchronous in bulk materials.