To see the other types of publications on this topic, follow the link: Fe-Cr.
Dissertations / Theses on the topic 'Fe-Cr'
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 'Fe-Cr.'
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
Lagerstedt, Christina. "Simulation of radiation damage in Fe and Fe-Cr." Licentiate thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-503.
Full text
2
Bin, Awais Hasan. "Phase relations in the Fe-Fe5Si3-Cr3Si-Cr region of the Fe-Cr-Si system." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678200.
Full text
3
Debili, Mohamed Yacine. "Contribution à l'étude microstructurale et cristallographique d'alliages fortement alliés de type Fe-Al, Fe-(Cr)-C, Fe-Cr-Ni et Ni-Cr-C solidifiés rapidement." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37604340d.
Full text
4
Ferguson, David Bruce. "Characterization of high damping Fe-Cr-Mo and Fe-Cr-Al alloys for naval ships application." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22942.
Full textAbstract:
The metallurgical basis for high damping in Fe-Cr-based alloys was investigated. Two alloys similar to VACROSIL-010 were studied, with compositions of 84.7 Fe-11.44 Cr-2.91 A1 and 84.8 Fe-11.65 Cr-2.92 Mo. The strain dependence of specific damping capacity (SDC) was evaluated using a modified version of the resonant dwell technique. Heat treatment variations were introduced by annealing in argon gas at temperatures between 950 C and 1100 C and then furnace cooling. Cantilever beam specimens were evaluated for SDC at their first three resonant modes (0-1,000 Hz) at room temperature. Changes in damping capacity were correlated with the results of tensile hysteresis testing and dilatometry. Keywords: Damping; Ship silencing; Ferritic stainless steels
5
Hu, Rong. "Irradiation effects on Fe-Cr alloys." Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.560928.
Full textAbstract:
Ferritic chromium steels are important structural materials for future nuclear fission and fusion reactors due to their advantages over traditional austenitic steels, including low swelling rates, better thermal fatigue resistance, and lower thermal expansion coefficients. Radiation-induced segregation or depletion (RIS/RID) of solute atoms at grain boundaries is considered to be a potentially significant phenomenon for structural materials because of its potentially detrimental role in affecting microstructure and furthermore mechanical properties. However, the behaviour of Cr at grain boundaries in ferritic steels is not well understood. Both segregation and depletion of Cr at grain boundary under irradiation have been previously observed and no clear dependency on irradiation condition or alloy type has been presented. Furthermore, ferritic alloys are known to undergo hardening and embrittlement after thermal aging in the temperature range of 300-550DC and this phenomenon is related with a and a' phase separation occurring in the solid solution. However the low temperature a-a' miscibility gap in the currently used phase diagram is extrapolated from high temperature results and conflicts with many experimental observations. To understand the Cr behaviour at gram boundaries in ferritic steels under irradiation, a systematic approach combining SEM/EBSD, FIB specimen preparation and APT analysis has been developed and successfully applied to a Fe- 15.2at%Cr to investigate the effect of pre-irradiation chemistry, grain boundary misorientation, impurities, irradiation damage, irradiation depth, and other possible factors to get a better understanding of RIS/RID phenomena. Both low sigma boundaries and randomly selected high angle boundaries have been investigated in detail. Systematic differences between the behaviour of different classes of boundaries had been observed, and the operating mechanisms are also discussed in this thesis. The maximum separation method has been applied on APT data to study the C- enriched clusters and Cr-enriched clusters, which were not directly visible on the atom maps. The composition of the Cr-enriched clusters was consistent with a' phase and the irradiation was found to accelerate the nucleation rather than the growth of these clusters. Such results provided important information in re- determining the a-a' phase boundary.
6
Pan, Li-Mei. "Phase equilibria and elastic moduli of rapidly solidified Fe-Cr-Mo-B and Fe-Cr-Ni-B alloys." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/2387/.
Full text
7
Kuksenko, Viacheslav. "Etude expérimentale d'alliages modèles Fe-Cr irradiés." Phd thesis, Université de Rouen, 2011. http://tel.archives-ouvertes.fr/tel-00664570.
Full textAbstract:
Afin d'améliorer la compréhension de l'évolution microstructurale des alliages Fe-Cr irradiés, alliages modèles des aciers ferrito-martensitiques (F-M) à haut Cr candidats comme matériaux de structure des réacteurs de génération IV, l'évolution de la microstructure a été étudiée à l'échelle nanométrique en fonction de la teneur en Cr et de la température d'irradiation. Deux séries d'expériences ont été réalisées: ● Des alliages modèles Fe-5%Cr, Fe-9%Cr et Fe-12%Cr irradiés aux neutrons à 300°C (température minimale de service pour les aciers F-M) jusqu'à 0.6dpa ont été analysés par sonde atomique 3D (3DAP). Ces analyses ont montré que les impuretés sont également impliquées dans l'évolution microstructurale de ces alliages sous irradiation. Deux familles indépendantes de clusters ont été observées : des clusters de NiSiPCr observés dans tous les alliages et des clusters riches en Cr correspondant à la phase α ' mais observés uniquement dans les alliages sursaturés en Cr (Fe-9%Cr et Fe-12%Cr). Ce travail a montré que l'apparition des clusters de NiSiPCr est induite par l'irradiation alors que celle des clusters riches en Cr est issue d'un processus accéléré par l'irradiation. Des enrichissements en Si, P et Cr ont été observés sur les lignes de dislocations ainsi que dans des joints de grain de faible et forte désorientation dans tous les alliages. ● Des alliages Fe-9%Cr et Fe-12%Cr ont été irradiés aux ions Fe + de 150 keV à 500°C (température maximale de service pour les aciers F-M). Des expériences de MET in situ entreprises jusqu'à une dose de 1.5 dpa, ont montré que le dommage apparaissait sous la forme de boucles de dislocations distribuées de façon homogène dans les grains. Dans les deux alliages modèles les boucles sont principalement du type <100>. L'analyse par 3DAP des mêmes alliages irradiés dans les mêmes conditions mais sous forme de pointes ne révèle aucune redistribution des espèces chimiques après irradiation.
8
Ho, Eileen Maria. "Studies of Fe/Cr magnetoresistive multilayer films." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320204.
Full text
9
Abdel-Mola, Mohamed Almokhtar M. "Magnetism of Cr thin films with 119Sn monolayers in Fe/Cr and V/Cr multilayers." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/150415.
Full text
10
Jung, Kyung Sub [Verfasser], and Eric J. [Akademischer Betreuer] Mittemeijer. "Nitriding of iron-based ternary alloys : Fe-Cr-Ti and Fe-Cr-Al / Kyung Sub Jung. Betreuer: E. J. Mittemeijer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2011. http://d-nb.info/1014148138/34.
Full text
11
Barthélémy, Agnès. "Etude des super-reseaux fe (001)/cr (001) et fe (001)/ag (001)." Paris 11, 1991. http://www.theses.fr/1991PA112032.
Full textAbstract:
Cette these presente l'etude experimentale de super-reseaux magnetiques fe/cr et fe/ag elabores par epitaxie par jet moleculaire. Dans les super-reseaux fe/ag nous avons mis en evidence la presence d'une forte anisotropie d'interface qui aligne l'aimantation perpendiculairement au plan des couches pour des epaisseurs de fe inferieures a 10 a. Cette anisotropie varie peu avec la temperature. Nous avons egalement etudie sur ces super-reseaux, la thermodynamique des systemes bidimensionnels a partir de la variation en temperature de l'aimantation. Dans le cas des super-reseaux fe/cr, nous nous sommes tout d'abord interesses au phenomene de couplage d'echange antiferromagnetique qui aligne antiparallelement les aimantations de deux couches de fe voisines. Nous avons etudie ce couplage par des mesures d'aimantation, de couple magnetique et de diffraction de neutrons et nous avons determine sa variation en fonction de l'epaisseur de cr et de la temperature. Cette these regroupe egalement les resultats experimentaux obtenus sur la dependance en epaisseur, en nombre de couche et en temperature d'une propriete nouvelle qui resulte de la structure en super-reseau: la magnetoresistance geante. Ce travail experimental s'accompagne du developpement d'un modele theorique de la magnetoresistance geante. Ce modele est semi-classique, de type fuchs-sondheimer, et permet de bien mettre en evidence les parametres importants qui regissent ce phenomene
12
Petroff, Frédéric. "Multicouches magnetiques fe/ag,fe/cr,co/cu,fe/cu : de l'elaboration aux proprietes magnetiques et electroniques." Paris 11, 1992. http://www.theses.fr/1992PA112487.
Full textAbstract:
Nous avons etudie la croissance et les proprietes magnetiques et electroniques de super-reseaux et multicouches magnetiques fe/ag, fe/cr, co/cu et fe/cu. Dans une premiere partie, nous decrivons l'elaboration des super-reseaux fe/ag sur les substrats gaas(001) et mgo(001) par la technique d'epitaxie par jets moleculaires. La caracterisation structurale des echantillons a ete menee in-situ par rheed et aes et ex-situ par diffraction x, exafs de surface et microscopie electronique. Les resultats obtenus par ces differentes techniques mettent en evidence la bonne qualite cristalline des super-reseaux fe/ag et montrent l'absence d'interdiffusion significative aux interfaces. Dans une deuxieme partie, nous abordons l'etude de deux proprietes specifiques des multicouches magnetiques: le couplage d'echange entre couches magnetiques et la magnetoresistance geante. Nous montrons que la magnetoresistance geante qui apparait dans les super-reseaux fe/cr est tres sensible a l'etat des interfaces. Par un traitement thermique ou par un melange intentionnel pendant la croissance, nous avons pu augmenter la magnetoresistance et mettre en evidence l'existence d'un optimum de rugosite aux interfaces. Nous avons aussi effectue une etude preliminaire de la forte variation en temperature de la magnetoresistance geante des super-reseaux fe/cr. Un modele phenomenologique, base sur les collisions electrons-magnons, permet d'expliquer cette dependance en temperature. Nous mettons en evidence le phenomene de magnetoresistance geante dans deux nouveaux systemes qui sont co/cu et fe/cu. Dans le systeme co/cu, une magnetoresistance de l'ordre de 50% est observee a temperature ambiante, prometteuse pour les applications. De plus, nous avons observe dans co/cu et fe/cu, des oscillations du couplage d'echange a travers le cuivre. Ces oscillations ont une periode voisine de 12 a dans les deux systemes mais sont en opposition de phase
13
Baghsheikhi, Saeed. "Spinodal Decomposition in the Binary Fe-Cr System." Thesis, KTH, Metallografi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37190.
Full textAbstract:
Spinodal decomposition is a phase separation mechanism within the miscibility gap. Its importance in case of Fe-Cr system, the basis of the whole stainless steel family, stems from a phenomenon known as the “475oC embrittlement” which results in a ruin of mechanical properties of ferritic, martensitic and duplex stainless steels. This work is aimed at a better understanding of the phase separation process in the Fe-Cr system. Alloys of 10 to 55 wt.% Cr , each five percent, were homogenized to achieve fully ferritic microstructure and then isothermally aged at 400, 500 and 600oC for different periods of time ranging from 30min to 1500 hours. Hardness of both homogenized and aged samples were measured by the Vickers micro-hardness method and then selected samples were studied by means of Transmission Electron Microscopy (TEM). It was observed that hardness of homogenized samples increased monotonically with increasing Cr content up to 55 wt.% which can be attributed to solution hardening as well as higher hardness of pure chromium compared to pure iron. At 400oC no significant change in hardness was detected for aging up to 1500h, therefore we believe that phase separation effects at 400oC are very small up to this time. Sluggish kinetics is imputed to lower diffusion rate at lower temperatures. At 500oC even after 10h a noticeable change in hardness, for alloys containing 25 wt.% Cr and higher, was observed which indicates occurrence of phase separation. The alloy with 10 wt.% Cr did not show change in hardness up to 200h which suggests that this composition falls outside the miscibility gap at 500oC. For compositions of 15 and 20 wt.% Cr only a small increase in hardness was detected even after 200h of aging at 500oC, which could be due to the small amounts of α´ formed. However, it means that alloys of 15 wt.% Cr and higher are suffering phase separation. For compositions inside the miscibility gap, hardening effect is a result of phase separation either by nucleation and growth or spinodal decomposition. To distinguish between these two mechanisms, TEM studies were performed and we found evidence that at 500oC the Fe-25 wt.% Cr sample decomposes by nucleation and growth while that of 35 wt.% Cr shows characteristics of the spinodal mechanism. For compositions inside the miscibility gap, with increasing Cr content up to 40% the change in hardness generally increased and for 45% and higher it always decreased. This suggests that the composition range corresponding to the spinodal region at 500oC is biased towards the Fe-rich side of the phase diagram. At 600oC only samples of 25, 30 and 35 wt.% Cr were studied because according to the previous studies, the spinodal boundary is most probably located in this composition range. However, no change in hardness was observed even up to 24h. We believe that this means the miscibility line lies below 600oC for alloys containing 35 wt.% Cr and lower. Further investigations are needed to confirm and explain this result.
14
Xu, Sen. "Characterisation of radiation damage in Fe-Cr-Alloys." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534015.
Full text
15
Cao, Siwei. "Determination of the Fe-Cr-Ni and Fe-Cr-Mo Phase Diagramsat Intermediate Temperatures using a NovelDual-Anneal Diffusion-Multiple Approach." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1377011410.
Full text
16
Elbiache, Abdelmoula. "Adsorption et ségrégation du soufre sur les alliages Fe-Cr-Ni et Fe-Cr-Ni-Mo : compositions superficielles, dissolution anodique et passivation." Paris 6, 1987. http://www.theses.fr/1987PA066357.
Full textAbstract:
Etude par spectrométrie Auger, rétrodiffusion d'ions et microanalyse par réactions nucléaires de l'adsorption du soufre à 970c sur les alliages Fe-17Cr-13Ni, Fe-17Cr-14,5Ni-2,5Mo. Analyse de la composition et de la structure des surfaces. Influence du soufre adsorbe ou dissous sur la dissolution anodique et la passivation des alliages. Examen des films passifs.
17
Raimondas, Kreivaitis. "Fe-C-Cr-B lydinių atsparumo abrazyviniam dilimui tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2007. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2007~D_20070816_154703-67221.
Full textAbstract:
Darbe analizuojamas abrazyvinio dilimo mechanizmas. Nustatomi šiems procesams didžiausią įtaką turintys veiksniai. Analizuojama abrazyvinių dalelių formos ir jų abrazyvumo vertinimo metodika. Apžvelgiami abrazyvinio dilimo modeliai. Abrazyvinių dalelių veikiami darbinių dalių paviršiai intensyviai dyla, todėl atsižvelgiant į jų darbo sąlygas būtina tinkamai parinkti jų savybes – kietumą, stiprumą bei sudėtį (legiravimą). Šių paviršių atnaujinimui ir sustiprinimui dažnai racionalu naudoti įvairios sudėties apvirinamus sluoksnius. Šio darbo tikslas – ištirti apvirintų kietųjų sluoksnių abrazyvinio dilimo ypatybes. Taip pat, ištirti lydinių abrazyvinio dilimo įtaką dylančio paviršiaus mikrogeometriniams parametrams. Atliktais tyrimais nustatyta legiruojančių elementų įtaka apvirintų sluoksnių abrazyviniam dilimui. Nustatyta optimali apvirinto sluoksnio sudėtis abrazyvinio dilimo sumažinimui. Tai pat nustatyta, kad termiškai apdirbtų plienų ir apvirintų sluoksnių dilimo atvejais nudilimas turi ryšį su paviršiaus parametru SPQP. Tuo remiantis, matuojant paviršiaus profilį, galima prognozuoti nudilimo dydį.There is analysis of abrasive wear mechanism in this work. The most important factors in these processes were established. There are analysed technique of abrasive particles properties and abrasive wear models. Surfaces witch are under the abrasive sway wear very fast. Considering to working conditions of these surfaces it is necessarily to choose there properties – hardness, strength and composition. For renovation and fortify of these surfaces it is often rational hard facing. The aim of this work was to estimate the influence of alloying elements content to abrasive wear. And estimate the abrasive wear influence to micro geometry of wearing surface. The influence of alloying elements to abrasive wear was estimated. To decrease abrasive wear the optimal chromium content in the arc welded alloy was investigated. Clear influence of heat treated steels and arc welded alloys abrasive wear on surface profile quality parameter SPQP is estimated. Considering with that we can measure surface profile and predict the wear rates.
18
Sorour, Ahmad. "Microstructure and tribology of Fe-Cr-B-based alloys." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123081.
Full textAbstract:
Wear causes loss of materials of moving parts and tools used in many fields. Wear can be reduced by employing appropriate materials and coatings, which requires an understanding of their microstructure, properties and tribological behavior. One of the high wear resistant materials is the Fe-Cr-B-based alloy system. Fe-Cr-B-based alloys have been fabricated using thermal spray, welding and sintering processes; and it has been found that their microstructure, properties and tribological performance vary from process to process. This dissertation focuses on advances made by employing recent processes to fabricate these alloys. The primary aim of this research is to understand the microstructure and tribology of the Fe-Cr-B-based alloys fabricated by the controlled short-circuit metal inert gas (CSC-MIG) welding and spark plasmasintering (SPS) processes.CSC-MIG was used to weld a Fe-28.2Cr-3.8B-1.5Si-1.5Mn (wt.%) cored wire alloy onto 1020 carbon steel substrate. SPS was employed to consolidate a Fe-45Cr-5.9B-2Si-0.1C (wt.%) gas-atomized powder alloy. Solidication behaviors of the gas-atomized powder and weldments were investigated through thermodynamiccalculations. Microstructure characterizations, hardness measurements and tribology testings were performed for these fabricated alloys.Upon cooling, the primary (Cr,Fe)2B phase began to form, followed by eutectic formation of the (Cr,Fe)2B and body-centered cubic (BCC) Fe-based solid solution phases. Because the powder contained a small amount of C, (Cr,Fe)7C3 was precipitated at the end of the solidication. The CSC-MIG weldment was composed of 44 wt.% primary and secondary orthorhombic (Cr,Fe)2B plates embedded in 56 wt.% BCC Fe-based solid solution, containing Fe, Cr, Mn and Si. The SPS specimen contained 65 wt.% (Cr,Fe)2B plates and 1 wt.% (Cr,Fe)7C3 precipitates dispersed in 34 wt.% BCC Fe-based solid solution, containing Fe, Cr and Si. The (Cr,Fe)2B phase was bigger in the weldment than the sintered specimen. The hardness of (Cr,Fe)2B was 24 GPa, independent of the alloy's composition and process parameters. As the B content increased, the fraction of (Cr,Fe)2B increased. As the (Cr,Fe)2B fraction increased, the bulk hardness of the specimens increased linearly. When the specimen's hardness and (Cr,Fe)2B size increased, abrasive wear resistance increased, while sliding wear resistance was independent of hardness but improved as the (Cr,Fe)2B size increased. The abrasive wear mechanism was microcutting, while sliding wear mechanisms were adhesion and mild oxidation.L'usage cause la perte du materiel de pieces mobiles et d'outils utilises dans plusieurs domaines. L'usage peut ^etre reduit en utilisant des materiaux appropries et des rev^etements dont l'utilisation demande la comprehension de leure microstructure, leures proprietes et leur comportement tribologique. Un des materiaux aillant une haute resistance a l'usage est le systeme d'alliage Fe-Cr-B. Les alliages a base Fe-Cr-B sont fabriques par pulverisation thermal, soudure et des processus de frittage. C'etait decouvert que la microstructure, les proprietes et la performance tribologique varie d'une procede a l'autre. Cette dissertation est centre sur les avances concues en utilisant des recentes procedes pour fabriquer ces alliages. Le but primaire de cette recherche est de comprendre la microstructure et la tribology des alliages Fe-Cr-B fabriques par soudure controlled short-circuit metal inert gas (CSC-MIG) et frittage ash (SPS).CSC-MIG etait utilise pour souder un alliage llamente Fe-28.2Cr-3.8B-1.5Si-1.5Mn (wt.%) sur un substrat d'acier 1020. SPS etait utilise pour consolider un alliage en poudre Fe-45Cr-5.9B-2Si-0.1C (wt.%) fabrique par atomization a gaz. Les comportements de solidication du poudre atomize par gaz et des soudures etaient etudies a travers des calculs thermodynamiques. Une caracterisation microstructurielle, des mesures de durete et des tests de tribology etaient performes pour ces alliages. Durant la refroidissement, la phase primaire (Cr,Fe)2B a commence a se developper suivi par une formation eutectique du (Cr,Fe)2B et de la phase en solution solide corps-centre cubique (BCC) a base de fer. Puisque la poudre contenait des petites quantites de C, le (Cr,Fe)7C3 a precipite a la n du solidication. La soudure CSC-MIG etait composee de plaques orthorhombiques de phase primaire et secondaire de (Cr,Fe)2B a 44 wt.% integre dans 56 wt.% d'une solution solide a base de Fe BCC content du Fe, Cr, Mn et Si. Le specimen prepare par SPS contenait des plaques de 65 wt.% (Cr,Fe)2B et des precipites de 1 wt.% (Cr,Fe)7C3 dispersees dans une solution solide a base de Fe BCC de 34 wt.% aillant du Fe, Cr et Si. La phase (Cr,Fe)2B etait plus grand dans la soudure que dans le specimen fritte. La durete du (Cr,Fe)2B etait 24 GPa sans dependance sur la composition de l'alliage ni les parametres de procede. Pendant que la quantite de B s'accroissait, la fraction du (Cr,Fe)2B s'accroissait aussi. Pendant que la fraction de (Cr,Fe)2B s'accroissait, la durete entiere des specimens s'accroissait d'une facon lineaire. Quand la durete du specimen et la taille du (Cr,Fe)2B s'accroissaient, la resistance abrasif d'usage s'accroissait pendant que la resistance glissant d'usage etait independant de la durete mais s'ameliorait pendant que la taille du (Cr,Fe)2B s'accroissait. Le mechanism de l'usage abrasif etait la microcoupure pendant que le mechanism de l'usage glissant etait l'adhesion de l'oxidation mineure.
19
Puga, Joel Bento. "WC-(Cu, Fe, Cr, Ni) composites attained by mechanosynthesis." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12263.
Full textAbstract:
Mestrado em Engenharia de MateriaisThis work aims to study the feasibility of replacing cobalt by copper and stainless steel in tungsten carbide composite. The composites were prepared with a binder content of 12 wt% using the powder metallurgy method in which the conventional milling was replaced by high energy ball milling. To obtain a composite with high density, good microstructure uniformity and controlled phase composition, suitable for a good mechanical performance, the processing conditions of the high energy ball milling (HEBM) and sintering methods were enhanced. Within the studied parameters, the prime milling conditions were found at the rotation speed of 350 rpm and ball-to-powder weight ratio of 20:1, varying the milling times between 8-10 hours for the studied compositions. The HEBM process was able to reduce the particle size of the composite powders down to the nanoscale and a good binder homogenization was reached. After compacting, the powders were submitted to vacuum sintering, in a temperature range of 1300 – 1500ºC followed by HIP (hot isotactic pressing). This procedure allowed attaining dense compacts and introduce efficiently copper in the stainless steel binder up to 30%, without substantial decrease of the sintered relative density. The WC-SS composite powders show a significant amount of M6C phase formed during sintering, endorsed by the high reactivity of the small powder particles and the appearing of the M6C phase. Adding copper to the WC-SS composite allowed the decrease of the M6C phase formation. The WC-Cu sintered samples revealed two distinct major phases, W2C and Cu0.4W0.6 and their appearance depends on the applied sintering technique, in the case of being conventional or two stages sintering, respectively. The mechanical characterization revealed that the hardness of the WC-SS compacts is equivalent to the reported values in the literature for WC-Co. On the other hand, the fracture toughness remains below the reference values. Nevertheless, it was possible to attain a good balance between hardness and fracture toughness in the WC-(SSCu) composites, which make them promising candidates for substituting the traditional WC-Co composite.
Este trabalho tem como objetivo estudar a viabilidade da substituição do ligante cobalto por cobre e aço inoxidável em compósitos de carboneto de tungsténio. Estes compósitos foram preparados com um teor de ligante de 12% pp, utilizando o método de pulverometalurgia no qual a moagem convencional foi substituída pela moagem de alta energia (MAE). Por forma a obter compósitos de elevada densidade, boa uniformidade microestrutural, e composição de fases adequada a um bom desempenho mecânico, foram otimizadas as condições de processamento das etapas de moagem de alta energia e da sinterização. As melhores condições de moagem foram verificadas com uma velocidade de rotação de 350 rpm, um rácio de peso bolas:material de 20:1 e, dependendo da composição estudada, um tempo de moagem variável entre 8 – 10 horas. Utilizando o processo de MAE foi possível reduzir o tamanho de partícula dos pós compósitos até à nanoescala e ainda obter uma boa uniformidade da distribuição da fase ligante. Após compactação, os pós foram submetidos a uma etapa de sinterização em vácuo num intervalo de temperaturas entre 1300 - 1500 °C, seguindo-se uma etapa de prensagem isostática a quente. Este método permitiu obter compactos de densidade elevada e introduzir de forma eficiente até 30% de cobre na fase ligante de aço inoxidável sem se verificarem reduções substanciais da densidade dos compactos sinterizados. Os compósitos de WC-SS apresentam uma composição de fases com uma quantidade elevada de fase M6C, formada durante a sinterização e que é favorecida nestes materiais, devido à elevada reatividade dos pós nanométricos. Contudo, a adição de cobre ao compósito WC-SS permitiu a diminuição da formação de fase M6C. As amostras sinterizadas de WC-Cu apresentam maioritariamente duas fases distintas, W2C e Cu0.4W0.6 e o aparecimento desta última fase depende da técnica de sinterização utilizada, convencional e sinterização em duas etapas respetivamente. A caracterização mecânica revelou que a dureza dos compósitos de WC-SS é equivalente aos valores indicados na literatura para os compósitos de WC-Co, enquanto a tenacidade permanece abaixo dos valores de referência. No entanto, foi possível alcançar um bom equilíbrio entre a dureza e tenacidade nos compósitos de WC-(SSCu), o que poderá permitir a sua utilização em algumas aplicações dos tradicionais carbonetos cementados de WC-Co.
20
Sorsh, Frans. "Assessment of creep damage in Fe-Ni-Cr alloys." Thesis, KTH, Hållfasthetslära (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259516.
Full textAbstract:
It is only a matter of time before components working in high temperature environments fail due to creep. Design for creep is therefore of vital importance to maximize the lifetime of components and reduce costs that may arise from maintenance and replacement of components. This thesis aims to use metallographical methods and finite element modeling to assess creep damage in a hydrogen reformer. The decommissioned reformer, made of Fe-Ni-Cr alloys, was investigated thoroughly via replica testing, hardness measurements as well as finite element modeling of the welds. An extended literature review was performed to gain a better understanding of creep in Fe-Ni-Cr alloys, welds and the modeling of creep generally. The microstructures of samples from the reformer were analyzed and mapped out in terms of creep damage which were then compared to a creep analysis of the welds with a simulation time of 100 000 h. The FE results yielded high stresses and creep strains with a maximum of 0.95% in the boundaries of the welds which gave realistic representations of strain distributions when compared to the metallographical results. Hardness measurement indicated that a relatively narrow zone with altered mechanical properties is present along the weld boundaries. This area, called the heat affected zone, was found to be most affected by creep with microcracks reaching maximum lengths of 2 mm. The creep strains obtained from simulation did not fall in line with the observed creep damage, it was thus concluded that a material model that considers tertiary creep would yield a more realistic representation in FEM for Fe-Ni-Cr alloys.Det är bara en tidsfråga innan komponenter som arbetar i högtemperaturförhållanden misslyckas pga kryp. Att designa med avseende på kryp är därmed viktigt för att maximera livslängden och reducera kostnader som kan komma från underhåll och från utbyte av komponenter. I detta examensarbete används metallografiska metoder och finita element modellering för att bedöma krypskador i en vätgasreformer. Vätgasreformern, som är tillverkad i Fe-Ni-Cr legeringar, togs ur drift och undersöktes metallografiskt med hjälp av replikprovning och hårdhetsprovning samt med finita element modellering av svetsar. En djupgående litteraturstudie utfördes för att öka förståelsen av kryp, specifikt i Fe-Ni-Cr legeringar och även modellering av kryp generellt. Mikrostrukturen från utvalda provbitar undersöktes och krypskador kartläggdes för att sedan jämföra med en krypanalys av svetsarna där 100 000 timmars kryp simulerades. Krypanalysen resulterade i höga spänningar och kryptöjningar upp till maximalt 0.95% i svetsgränserna vilket gav realistiska representationer av töjningsdistributionen jämfört med metallografiska resultaten. Hårdhetsmätningar indikerade att ett smalt område med förändrade mekaniska egenskaper fanns utmed svetsgränserna. Detta område, den värmepåverkade zonen, var mest utsatt för krypskador med mikrosprickor uppemåt 2 mm i längd. Kryptöjningar som erhölls från simuleringen gav inte en tillräckligt bra uppskattning av kryptöjningarna – de krypskador som observerades motsvarar lokalt högre töjning. Slutsatsen är att en materialmodell som tar hänsyn till tertiärkryp skulle i det här fallet ge en mer realistisk representation i FEM för Fe-Ni-Cr legeringar.
21
Nguyen, Van Dau Frédéric. "Élaboration et propriétés magnétiques de multicouches Ag/Fe et Cr/Fe épitaxiées sur GaAs(001)." Paris 11, 1989. http://www.theses.fr/1989PA112081.
Full textAbstract:
Étude de la croissance des multicouches par la technique d'épitaxie par faisceau moléculaire. Les relations épitaxiales sont déterminées in situ par diffraction d'électrons rapides en incidence rosante. Caractérisation des interfaces par profil Auger et microscopie électronique à balayage en transmission. Mesures d'aimantation, de couple magnétique, de magnétorésistance et d'effet Hall.
22
Ravlić, Robert. "Magnetische Studien der Cr(001)-Oberfläche und des Fe-Cr(001)-Systems mittels spinpolarisierter Rastertunnelspektroskopie." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968651593.
Full text
23
GUILLEMOT, MAUD. "Nouveaux composes modeles pour l'electronique moleculaire en serie fe-cr-fe isolables sous 4 degres d'oxydation." Rennes 1, 1998. http://www.theses.fr/1998REN10172.
Full textAbstract:
Cette these presente la synthese et l'etude d'une nouvelle famille de complexes bimetalliques a pont butadiynediyle, (c#5me#5)fe(dippe)#2(cccc)#n#+, stables et isolables sous quatre degres d'oxydation, ainsi que celles des nouveaux complexes a pont butatrienylidene stables (c#5me#5)(dippe)fe(=c=c=c=c(r))fe(co)#2(c#5me#5)#+x# r = h, me). Ces composes sont de bons modeles pour l'electronique moleculaire. L'acces aux complexes butatrienylidenes s'effectue par addition electrophile sur le complexe de type donneur-accepteur (c#5me#5)(dippe)fe(cccc)fe(co)#2(c#5me#5). Les complexes (c#5me#5)(dippe)fe(=c=ch#2)#+pf#6#, (c#5me#5)(dippe)fe(cch), (c#5me#5)(dippe)fe(ccccsime#3), et (c#5me#5)(dippe)fe(cccch) sont obtenus a partir du complexe (c#5me#5)(dippe)fecl. La complexation de la chaine en c#4 avec le compose (c#5me#5)(dippe)fecl a conduit au complexe neutre (c#5me#5)fe(dippe)#2(cccc). L'oxydation en cascade du complexe (c#5me#5)fe(dippe)#2(cccc) conduit aux composes mono-, bi- et tri-oxyde, qui ne different entre eux que par leur nombre total d'electrons de valence. L'etude en voltametrie cyclique du complexe (c#5me#5)fe(dippe)#2(cccc) a permis la determination des plus fortes valeurs de kc connues a ce jour pour un complexe bimetallique a 5 liaisons pontantes. Les structures radiocristallographiques des composes mono- et tri-oxyde ont ete etablies par diffraction aux rayons x. Les spectroscopies infra-rouge, mossbauer, r. P. E, et proche infra-rouge ont montre que la vitesse du transfert d'electron du complexe a valence-mixte est ralentie a l'etat solide ; elle est comprise entre 10#7 et 10#1#1 s##1. Le complexe monocationique est un compose de classe iii en solution et de classe ii a l'etat solide. Les proprietes magnetiques ont permis d'etablir la structure electronique des composes oxydes. Un equilibre singulet-triplet caracterise le compose bicationique et un equilibre doublet-quartet le compose tricationique. Les proprietes en optique non lineaire de ces complexes ont revele un influence de la position des greffons organometalliques sur la valeur de.
24
Zhou, Jing. "Experimental study of phase separation in Fe-Cr based alloys." Licentiate thesis, KTH, Metallografi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119230.
Full textAbstract:
Duplex stainless steels (DSSs) are important engineering materials due to their combination of good mechanical properties and corrosion resistance. However, as a consequence of their ferrite content, DSSs are sensitive to the so-called ‘475°C embrittlement’, which is induced by phase separation, namely, the ferrite decomposed into Fe-rich ferrite (α) and Cr-rich ferrite (α'), respectively. The phase separation is accompanied with a severe loss of toughness. Thus, the ‘475°C embrittlement’ phenomenon limits DSSs’ upper service temperature to around 250°C. In the present work, Fe-Cr binary model alloys and commercial DSSs from weldments were investigated for the study of phase separation in ferrite. Different techniques were employed to study the phase separation in model alloys and commercial DSSs, including atom probe tomography, transmission electron microscopy and micro-hardness test. Three different model alloys, Fe-25Cr, Fe-30Cr and Fe-35Cr (wt. %) were analyzed by atom probe tomography after different aging times. A new method based on radial distribution function was developed to evaluate the wavelength and amplitude of phase separation in these Fe-Cr binary alloys. The results were compared with the wavelengths obtained from 1D auto-correlation function and amplitudes from Langer-Bar-On-Miller method. It was found that the wavelengths from 1D auto-correlation function cannot reflect the 3D nano-scaled structures as accurate as those obtained by radial distribution function. Furthermore, the Langer-Bar-On-Miller method underestimates the amplitudes of phase separation. Commercial DSSs of SAF2205, 2304, 2507 and 25.10.4L were employed to investigate the connections between phase separation and mechanical properties from different microstructures (base metal, heat-affected-zone and welding bead) in welding. Moreover, the effect of external tensile stress during aging on phase separation of ferrite was also investigated. It was found that atom probe tomography is very useful for the analysis of phase separation in ferrite and the radial distribution function (RDF) is an effective method to compare the extent of phase separation at the very early stages. RDF is even more sensitive than frequency diagrams. In addition, the results indicate that the mechanical properties are highly connected with the phase separation in ferrite and other phenomena, such as Ni-Mn-Si-Cu clusters, that can also deteriorate the mechanical properties.QC 20130308
25
EverhartC, Charles. "The Electrodeposition of Fe-Ni-Cr Alloys from Aqueous Electrolytes." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1252092401.
Full textAbstract:
Thesis(M.S.)--Case Western Reserve University, 2009Title from PDF (viewed on 2010-01-28) Department of Chemical Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
26
Koseki, Toshihiko 1958. "Undercooling and rapid solidification of Fe-Cr-Ni ternary alloys." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12040.
Full text
27
Flores, Carlos D. (Carlos Daniel). "Evaluation of radiation induced segregation in Fe-Ni-Cr alloys." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/44597.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994.Includes bibliographical references.
by Carlos D. Flores.
M.S.
28
Hardie, Christopher David. "Micro-mechanics of irradiated Fe-Cr alloys for fusion reactors." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a3ac36ba-ca6f-4129-8f37-f1278ef8a559.
Full textAbstract:
In the absence of a fusion neutron source, research on the structural integrity of materials in the fusion environment relies on current fission data and simulation methods. Through investigation of the Fe-Cr system, this detailed study explores the challenges and limitations in the use of currently available radiation sources for fusion materials research. An investigation of ion-irradiated Fe12%Cr using nanoindentation with a cube corner, Berkovich and spherical tip, and micro-cantilever testing with two different geometries, highlighted that the measurement of irradiation hardening was largely dependent on the type of test used. Selected methods were used for the comparison of Fe6%Cr irradiated by ions and neutrons to a dose of 1.7dpa at a temperature of 288°C. Micro-cantilever tests of the Fe6%Cr alloy with beam depths of 400 to 7000nm, identified that size effects may significantly obscure irradiation hardening and that these effects are dependent on radiation conditions. Irradiation hardening in the neutron-irradiated alloy was approximately double that of the ion-irradiated alloy and exhibited increased work hardening. Similar differences in hardening were observed in an Fe5%Cr alloy after ion-irradiation to a dose of 0.6dpa at 400°C and doses rates of 6 x 10-4dpa/s and 3 x 10-5dpa/s. Identified by APT, it was shown that increased irradiation hardening was likely to be caused by the enhanced segregation of Cr observed in the alloy irradiated with the lower dose rate. These observations have significant implications for future fusion materials research in terms of the simulation of fusion relevant radiation conditions and micro-mechanical testing.
29
Roosmark, Viking. "Modelling of spinodal decomposition in the binary Fe-Cr system." Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190729.
Full textAbstract:
Spinodal decomposition is a phenomenon which hinders the usage of ferrite containing steels under certain conditions. With a better understanding and knowledge of spinodal decomposition new ferritic and duplex stainless steels could be designed. The project is divided into two parts, an experimental part and a theoretical part. The aim of the theoretical part was to compare simulated values of the amplitude and wavelength of spinodal decomposition, obtained from solving the Cahn-Hilliard equation with other experimental values. The experimental part is performed as to determine the chemical diffusion coefficient and the mobility of Fe and Cr in the binary Fe-Cr system for lower temperatures using the Boltzmann-Matano method from chemical profiles of different samples. Another purpose with the project is to determine if the methods and the approach which are taken is viable and useful for calculating diffusion coefficients and if it can be used in studies to come. The simulations were in good agreement with other data at higher time intervals, but deviates at lower times. The calculated interdiffusion coefficients were in all cases lower than the expected values and as such the conclusion that is drawn is that the methods which are used could need further development.Spinodalt sönderfall är ett fenomen som hindrar användningen av stål som innehåller ferrit under vissa förutsättningar. Med en större förståelse och mer kunskap om spinodalt sönderfall så kan nya ferritiska och duplexa rostfria stål utformas. Projektet är uppdelat i två delar, en experimentell del och en teoretisk del. Syftet med den teoretiska delen var att jämföra simulerade värden av amplituden och våglängden för spinodalt sönderfall, vilka erhölls från att lösa Cahn-Hilliard ekvationen med andra experimentella värden. Den experimentella delen utförs för att bestämma kemiska diffusionskoefficienter för Fe och Cr i det binära Fe-Cr system för lägre temperaturer med hjälp av Boltzmann-Matano metod från kemiska profiler av olika prover. Ett annat syfte med projektet är att ta reda på om de metoder och tillvägagångssätt som tas är livskraftiga och användbara för beräkning av diffusionskoefficienter och om den kan användas i studier framöver. Simuleringarna var i god överensstämmelse med annan experimentel data vid högre tidsintervall, men avviker vid lägre tider. De beräknade Interdiffusion koefficienterna var i samtliga fall lägre än de förväntade värdena och som sådan, dras slutsatsen att de metoder som används kan förbättras.
30
Techaboonanek, Chanachon. "Precipitation during Tempering of Martensite in Fe-Cr-C alloys." Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103192.
Full textAbstract:
The martensite structure is the most important microstructure in tool steel due to its high hardness. However, a lack of ductility is the major drawback. In order to improve the ductility and still maintaining a suitable hardness a tempering process is needed. The tempering process will cause recovery and recrystallization in the matrix, and moreover carbides will precipitate. The specific carbides have different characteristics and thus the type of carbide formed during tempering is very important for the properties of the steel. The simulation software (TC-Prisma) is interesting because it can predict type, size, and amount of carbides. The present study was carried out to investigate both the microstructure, hardness evolution of martensite and precipitation which occurred in Fe-C-Cr steel with different compositions, tempered at 700oC. The experimental results were compared with simulation results. Micro-Vickers hardness test with a load of 100 g was used and the hardness value dropped 40% and 60% in low carbon alloy and high carbon alloy steels, respectively. The significant drop occurred during the first 30 seconds of tempering due to recovery of the matrix. Hardness values slightly decreased and then stabilized during continued tempering. The microstructure of martensite and the morphology of carbides at different tempering times were examined by scanning and transmission electron microscopy in order to study the precipitation of carbides from the nucleation and growth to coarsening. There are three types of carbides which precipitated in the Fe-C-Cr specimens: M7C3, cementite and M3C2 depending on the composition. Fe-0.16C-4.05Cr contained M7C3, Fe-0.95C-1.065Cr contained cementite and M3C2 and Fe-014C-0.983Cr and Fe-0.88C-4.12Cr contained M7C3 and cementite. M7C3 has a faceted shape and precipitates referentially at grain boundaries. On the other hand, cementite has an elongated shape and precipitated mainly at grain boundaries but also intragranulary. M3C2 has a rounded shape and was seen only in very small amounts, and seemed to precipitate at random sites. The trend of carbide growth in experiments is consistent with the simulations using TC-Prisma, but more work is needed to enable quantitative comparisons.
31
Gregolin, Jose Angelo Rodrigues. "Desenvolvimento de ligas Fe-C-Cr-(Nb) resistentes ao desgaste." [s.n.], 1990. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265497.
Full textAbstract:
Orientador : Nelson Guedes de AlcantaraTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas
Made available in DSpace on 2018-07-14T02:08:21Z (GMT). No. of bitstreams: 1 Gregolin_JoseAngeloRodrigues_D.pdf: 7272657 bytes, checksum: 9570b8db39232cea6fded9a3eaea20fd (MD5) Previous issue date: 1990
Resumo: São apresentados os resultados de uma pesquisa sobre o desenvolvimento de ligas Fe ¿ C ¿ Cr e Fe ¿ C ¿ Cr ¿ Nb que representam classes importantes de materiais para aplicações contra o desgaste abrasivo. As ligas experimentais foram elaboradas em forno de indução e vazadas em moldes de areia. Ensaios abrasivos por sílica a baixas tensões, com equipamento de roda de borracha, foram realizados para a determinação de perdas de massa e de volume dos materiais. Empregou-se uma técnica de microscopia eletrônica de varredura na observação de superfícies progressivamente desgastadas. Também foram realizadas análises térmicas de solidificação de ligas, com o emprego de forno de aquecimento resistivo e interrupção de solidificação por congelamento da amostra. Com relação ás microestruturas destes materiais, a série de ligas Fe ¿ C ¿ Cr apresentou matriz austenítica (?) e carbonetos M7C3 variando entre 8,7% a 47,7%, abrangendo desde estruturas hipoeutéticas até hipereutéticas. A série de ligas Fe ¿ C ¿ Cr ¿ Nb apresentou as fases ?, M7C3 e NbC em duas configurações microestruturais típicas, com a formação de ? dendrítico ou de carbonetos M7C3 massivos. As ligas da série ao Nb contendo ? dendrítico apresentaram desde 1,5 até 22,2% NbC (em um total de 27,9 até 44,1% de carbonetos M7C3 + NbC). As ligas da série ao Nb contendo M7C3 massivo apresentaram desde 1,2 7 3 até 20,5% NbC (em um total de 36,5 até 45,1% de carbonetos M7C3 + NbC). Investigou-se a variação do desgaste com a porcentagem volumétrica de carbonetos presentes na microestrutura destes materiais. Verificou-se um mínimo de desgaste para frações intermediárias de carboneto M7C3 nas ligas Fe ¿ C ¿ Cr, para microestrutura ligeiramente hipereutética. Também foi verificado um mínimo de desgaste para fração intermediária do total de carbonetos M7C3 + NbC para as ligas Fe ¿ C ¿ Cr ¿ Nb. Para auxiliar na interpretação dos resultados quantitativos de desgaste, foram observados os micromecanismos superficiais de desgaste. As diferentes formas de degradação microestrutural em geral se mostraram semelhantes para as ligas Fe ¿ C ¿ Cr e Fe ¿ C ¿ Cr ¿ Nb. Entretanto, podem ser salientadas duas diferenças importantes no desgaste de NbC e M7C3. O NbC não apresentou ilhas de matriz austenítica confinadas em seu interior, ao contrário do M7C3 massivo que apresentou essa formação microestrutural e o mecanismo de fragmentação por pite associado. Por outro lado, os carbonetos NbC massivos mostraram-se sujeitos a um arrancamento ou desintegração acentuada, enquanto que os carbonetos M7C3 massivos apresentaram degradação sempre gradual. Para a previsão e interpretação da formação das microestruturas obtidas nas ligas da série contendo Nb, foi desenvolvido um modelo de equilíbrio e solidificação de fases. O modelo previu por exemplo, os campos de formação de ? dendrítico ou M7C3 massivo, presentes de forma mutuamente excludentes e todas as ligas contendo NbC investigadas. O modelo fundamentou-se no sistema Fe ¿ C ¿ Cr ¿ NbC.
Abstract: The Fe - C - Cr e Fe - C - Cr - Nb alloys, extensively used for abrasive wear resistance applications, were developed and studied in the present work. These experimental alloys were induction melted and sand cast. Low stress rubber wheel abrasion tests with silica were performed for mass and volume loss measurements. Scanning electronic microscopy was use for observing wear damages on the material's surface. Thermal analysis were conducted by heating some alloys in a SiC resistance furnace and water quenching for freezing structures. The Fe - C - Cr alloy microstrutures showed austenitic (?) matrix and 8,7% to 47,7% M7C3 carbides going from hipoeutetic to hipereutetic structures. The Fe - C - Cr alloys exibited ?, M7C3 and NbC in two different microstructural configurations. One of them showed dendritic ? and the other massive M7C3 . The Nb alloys with dendritic ? showed 1,5 to 22,2% NbC (in a total of 27,9% to 44,1% M7C3 + NbC), whilst the Nb alloys with massive M7C3 showed 1,2 to 20,5% NbC (in a total of 36,5 to 45,1% M7C3 + NbC). The influence of carbide volume fraction on the wear behavior was investigated, and a minimum wear was observed for intermediate volume fraction of M7C3 in Fe - C - Cr alloys corresponding to a slightly hipereutetic microstructure. The same behavior was also verified at intermediate M7C3 + NbC carbide volume fraction for the Nb alloys. For a better understanding o the above quantitative results SEM observations were performed, attention being centered on the evolution of the wear morphology and thus on the micromechanism involved in the process. Although the general features were almost identical, two main differences were observed, regarding the fracture mode of massive NbC and M7C3 . First, austenitic matrix islands were observed within M7C3 carbide, which exibited pit formation mechanism, while no such microstructural feature was associated to NbC. Second, evidences of NbC gross fracture were often found while massive M7C3 was characterized by progressive degradation. In order to rationalize the Nb alloys microstruture formation, a phase equilibrium diagram and a solidification model were developed based on a Fe - C - Cr - NbC system. The ? dendritic and massive M7C3 solidification fields for the experimental Nb alloys were explained by this model
Doutorado
Doutor em Engenharia Mecânica
32
Higginson, A. "The passivation of Fe-Cr-Ru alloys in acidic solutions." Thesis, University of Manchester, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488143.
Full text
33
Osso, Dominique. "Élaboration de nanocomposites alumine-métal (Fe, Cr, Ni) par mécanosynthèse." Vandoeuvre-les-Nancy, INPL, 1995. http://docnum.univ-lorraine.fr/public/INPL_T_1995_OSSO_D.pdf.
Full textAbstract:
Des matériaux composites alumine-alliages (Fe, Cr, Ni) ont été élaborés par mécanosynthèse. Ces poudres composites sont obtenues par broyage réactif à haute énergie d'un mélange de poudres d'aluminium et d'oxydes métalliques. Les matériaux ainsi synthétisés ont la caractéristique d'être des matériaux à grains nanocristallins. Les mécanismes réactionnels, intervenant lors du broyage, pour des systèmes simples alumine-métal et pour des systèmes complexes alumine-alliages ont été étudiés. Un large domaine de composition de la phase métallique est abordé. Le broyage réactif en présence de fluide est aussi étudié ainsi que l'effet d'une activation mécanique sur la réaction d'oxydoréduction. Un schéma d'interprétation simple est proposé pour expliquer les observations. Les évolutions à haute température des poudres ainsi obtenues sont présentées. Nous nous intéressons plus particulièrement à l'évolution de la composition chimique des phases, à la croissance des grains et à la microstructure des poudres consolidées soit par frittage classique soit par frittage sous charge
34
Dahlström, Alexander. "Influence d'une contrainte mécanique sur le vieillissement d'alliages Fe-Cr." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR039/document.
Full textAbstract:
L’acier inoxydable est un alliage important pour le développement technique d’une société moderne; cela a été découvert au début du 20ème siècle. Cependant, leur système d'alliage de base, Fe-Cr, est affecté par une lacune de miscibilité à basse température (<600 °C) présent dans le diagramme de phases. Les alliages présentant une lacune de miscibilité dans leur diagramme de phase ont tendance à se décomposer. Ce phénomène également connu sous le nom de "fragilisation à 475 °C", est d’une importance technique, car la décomposition modifie les propriétés mécaniques de ces alliages; dans ce cas présente, par la perte de ductilité et de résistance aux chocs. La tendance à la décomposition augmente avec la diminution de la température, ce qui limite la température de service supérieure à environ 300 °C, limitant ainsi la durée de vie de ces alliages. Étant donné que la fragilisation peut provoquer une défaillance soudaine de ces alliages, cet aspect nuit à leur utilisation en tant que composants structurels dans les secteurs du transport et de l’énergie. La décomposition des alliages Fe-Cr pose un défi aux techniques de caractérisation traditionnelles, car les variations de composition se produisent à l'échelle nanométrique. Par conséquent, la sonde atomique tomographique de pointe a été utilisée pour étudier ces variations de composition à l'échelle atomique en 3D. La modélisation atomistique corrélative a été utilisée pour améliorer davantage la compréhension du processus de décomposition dans ces alliages ; ce modèle était basé sur la théorie de la fonction de densité atomique. Pour émuler la décomposition améliorée du matériau, causée par la température et/ou une charge externe, la décomposition dans ce projet est stimulée par une température de service supérieure à la normale. Dont la nécessité de connaître la limite exacte de la lacune de miscibilité. Ainsi, la nécessité d'évaluer la limite supérieure de température de cette décomposition dans le système Fe-Cr est née de résultats non concluants des analyses de la littérature existant. Par conséquent, un four de haute précision en combinaison avec une sonde atomique tomographique a été utilisé pour étudier la décomposition et l’agglomération dans le système Fe-Cr d’une manière plus précise que jamais. En outre, d’explorer en détail l’emplacement de la limite de la lacune de miscibilité. La décomposition de ces alliages au cours du vieillissement modifie les propriétés mécaniques. Ainsi, en raison de leur utilisation en tant que composants structurels, le comportement de décomposition dû au vieillissement a été étudié, ainsi que le vieillissement dû à la charge externe. Cette dernière situation se rencontre également dans des applications réelles pendant le service, émulées par le vieillissement dû à la pression en utilisant une simple force de traction. Afin d'examiner en détail l'effet de la pression externe, l'orientation du grain par rapport à la direction de traction a été prise en compte lors d'un simple vieillissement thermique et lors de l’application d’une force de traction continue. Ainsi, l'orientation cristallographique et les niveaux de charge ont été pris en compte pour leur effet sur le processus de décomposition/dégradationStainless steel is an important alloy for the technical development of a modern society, they were discovered in the early 20th century. However, their base alloying system, Fe-Cr, is affected by a low temperature (<600°C) miscibility gap present in the phase diagram. Alloys with a miscibility gap in their phase diagram tend to decompose. This phenomenon is also known as the “475°C embrittlement”, it is of technical importance as decomposition alters the mechanical properties of these alloys, in this specific case, by loss of ductility and impact toughness. The tendency to decompose increases with decreasing temperature, restricting the upper service temperature to around 300°C and limiting the service lifetime of these alloys. Because embrittlement can cause sudden failure of these alloys, this phenomenon is detrimental to their use as structural components in transportation and energy industry. The decomposition of Fe-Cr alloys poses a challenge for traditional characterisation techniques, as composition variations occur at the nanoscale. Therefore, the state-of-the-art atom probe tomography have been utilised to study these composition variations at the atomic scale in 3D. Correlative atomistic modelling has been used to further enhance the understanding of the decomposition process in these alloys, this model was based on atomic density function theory. To emulate enhanced decomposition of the material, caused by temperature and/or an external load, decomposition in this work is stimulated by a higher than the normal service temperature. Hence, a need to know the exact limit of the miscibility gap. Thus, a need to evaluate the upper-temperature limit of this decomposition in the Fe-Cr system arose from inconclusive results in the literature. Hence, a high precision furnace in combination with atom probe was utilised to study decomposition and clustering in the Fe-Cr system more accurately than ever before. Furthermore, to explore in detail the location of the limit of the miscibility gap. The decomposition of these alloys during ageing alter the mechanical properties. Thus, due to their use as structural components, the decomposition behaviour during ageing was investigated, as well as ageing during external load. This last situation is also encountered in real applications during service, mimicked by stress-ageing using a simple tensile force. In order to in detail investigate the effect of the external stress, grain orientation with respect to the tensile direction was considered during simple thermal ageing, and during the constantly applied tensile force. Thus, crystallographic orientation and load levels were considered for their effect on the decomposition process
35
Babu, Sudarsanam Suresh. "Acicular ferrite and bainite in Fe-Cr-C weld deposits." Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/221886.
Full text
36
Payne, Matthew A. "High-throughput Screening of Alloy Oxidation Across Al-Fe-Ni and Al-Fe-Ni-Cr Composition Space." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/863.
Full textAbstract:
The high-temperature oxidation of multicomponent metal alloys involves complex kinetic processes that are not fully understood for many systems. As a result, prospective alloy compositions must typically be screened experimentally during the design of oxidation-resistant alloys. The comprehensiveness with which this can be done has conventionally been limited by the time required to prepare and test large numbers of single-composition alloy samples. This thesis describes the development, implementation, and assessment of a high-throughput methodology for studying the compositional dependence of alloy oxidation using composition spread alloy films (CSAFs), compact samples containing continuous, lateral gradients in composition. High-throughput analyses of the oxidation behavior of many different alloy compositions can be performed with a single CSAF by using spatially resolvable characterization techniques to probe different locations across its surface. We have used CSAFs to study the oxidation of aluminum-iron-nickel (Al-Fe-Ni) and aluminum-iron-nickel-chromium (Al-Fe-Ni-Cr) alloys. Given a minimum “critical Al concentration”, 𝑁Al∗, these alloys preferentially form a surface layer of Al2O3 upon initial exposure to an oxidizing environment, which provides substantial protection to the underlying metal against further oxidation. However, the value of 𝑁Al∗ can vary as a function of both multicomponent composition and the thermochemical identity of the oxidizing environment. By oxidizing CSAFs in dry or humid air at 427 °C, we have identified continuous boundaries through the Al-Fe-Ni and Al-Fe-Ni-Cr composition spaces where phenomenological transitions in oxidation behavior occur, including 𝑁Al∗ boundaries delineating the compositional limits for protective Al2O3 formation. The results demonstrate the potential of CSAF-based methods to screen with unprecedented detail the effects of composition on multicomponent alloy oxidation, and offer important fundamental insights into its mechanisms.
37
Carvalho, Fernanda Raquel. "Redução fotocatalítica de Cr(VI) e adsorção de Cr(III) pelo compósito magnético Fe-TiO 2 -Ag." Universidade Federal de Viçosa, 2016. http://www.locus.ufv.br/handle/123456789/13252.
Full textAbstract:
Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-11-17T17:13:09Z
No. of bitstreams: 1
texto completo.pdf: 1125978 bytes, checksum: 943ab1e68d5c423db641e29cac7f50e2 (MD5)Made available in DSpace on 2017-11-17T17:13:09Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1125978 bytes, checksum: 943ab1e68d5c423db641e29cac7f50e2 (MD5) Previous issue date: 2016-08-10
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O compósito calcinado Fe-TiO 2 -Ag foi preparado e utilizado na fotorredução de Cr(VI) de soluções aquosas e de efluentes de galvanoplastia. Os catalisadores foram caracterizados por microscopia eletrônica de varredura (MEV), espectroscopia de raio-X (DRX), espectroscopia de infravermelho (IV), espectroscopia Raman, espectroscopia de reflectância difusa (ERD) e espectroscopia de massas com plasma indutivamente acoplado (ICP-MS). A atividade fotocatalítica foi verificada em soluções de Cr(VI) (30 mg L -1 ), onde foram obtidos aproximadamente 100% de redução, em 120 minutos, quando submetida a radiação artificial (λ > 300 nm), e 85% de remoção, em 270 minutos, na presença de radiação solar em um dia de inverno. Não foram observadas diferenças significativas quando o catalisador foi utilizado em um efluente real de galvanoplastia, indicando que a fotorredução de Cr(VI) não é afetada por possíveis interferentes deste efluente. A impregnação da prata culminou em uma melhoria na atividade do fotocatalisador, que passou a absorver radiação visível. A introdução do óxido de ferro tornou o catalisador completamente magnético, facilitando sua retirada da solução ao término do processo pela aplicação de um simples campo magnético. As condições experimentais foram investigadas para a otimização da proporção mássica de prata (15%), de óxido de ferro (10%), pH (2), dosagem do catalisador (1 g L -1 ) e o efeito da calcinação, que provocou um aumento na área superficial do catalisador, melhorando sua atividade. Verificou-se ainda que a cinética de fotorredução do Cr(VI) segue um modelo de pseudoprimeira ordem e que a quantidade máxima de Cr(III) adsorvida é de aproximadamente 72 mg g -1 . A boa estabilidade apresentada pelo compósito Fe-TiO 2 -Ag calcinado, permitindo sua reutilização por até 5 ciclos com pequena perda na atividade, somada ao fato de ser magnético, não sofrer interferências de outros metais e poder ser usado sob radiação solar torna possível a aplicabilidade prática deste fotocatalisador na indústria.
Fe-TiO 2 -Ag calcined composite was prepared and used for photo- reduction of Cr(VI) from aqueous solution and electroplating wastewater. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy (DRS) and inductively coupled plasma mass spectroscopy (ICP-MS). The photocatalytic activity was investigated for Cr(VI) (30 mg L -1 ) solutions, in which it was obtained almost 100% of reduction, in 120 minutes, under artificial irradiation (λ > 300 nm), and 85% removal, after 270 minutes, under solar irradiation in a winter’s day. There were no significant differences when the catalyst was used for an industrial electroplating wastewater, indicating that the photo-reduction of Cr(VI) is not affected by possible interference in this industrial effluent. Silver doping improves the photocatalytic activity, inducting visible light radiation absorption. The introduction of iron oxide turned the catalyst completely magnetic, facilitating its removal from solution, after the end of the procedure, with a simple application of a magnetic field. The experimental conditions have been investigated for the optimization of mass proportion of loading silver (15%) and iron oxide (10%), pH (2), catalyst dosage (1 g L -1 ) and the effect of calcination, which results in an increase in the catalyst’s surface area, improving its activity. It was also verified that the Cr(VI) photo-reduction obeys to a pseudo first order kinetic and the maximum adsorption capability for Cr(III) was about 72 mg g -1 . The good stability showed by the calcined composite Fe-TiO 2 -Ag, allowing its reutilization for 5 cycles with small loss in activity, added to the fact of being magnetic, not affected by other metal interfering and with the possibility of be used under solar irradiation, support the practical industrial applicability of this photo-catalyst.
38
Olden, Vigdis. "FE modelling of hydrogeninduced stress crackingin 25% Cr duplex stainless steel." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5026.
Full text
39
Azcoitia, Christian. "Effets magnétomécaniques dans des alliages ferromagnétiques du type Fe-Cr-X /." [S.l.] : [s.n.], 2002. http://library.epfl.ch/theses/?nr=2531.
Full text
40
Liotti, Enzo. "Microstructural characterisation of a bulk, spraycast Al-Fe-Cr-Ti alloy." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8508.
Full textAbstract:
Legislative and environmental demands are increasing the pressure on transport industries to introduce vehicles with lower weight, greater efficiency and reduced emissions while remaining competitive. For these reason the aerospace, defence and automotive industries worldwide are unanimous in the call for the development of new alloys with a step-change in performance. In the present thesis the results of the thorough microstructural and mechanical properties investigation of a 19 kg spraycast billet of the normally nanoquasicrystalline containing composition Al93Fe3Cr2Ti2 produced at Oxford University along with three binary Al intermetallics: Al3Ti, Al13Cr2 an Al13Fe4 produced by suction casting in the form of 5 mm rods at Sheffield University are presented and discussed.
41
Baxter, A. G. "The oxidation and carburisation of Fe-9%Cr-1%Mo steel." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234829.
Full textAbstract:
The mechanisms involved in the breakdown of the protective ccides formed on Fe-9%Cr l%Mo have been investigated in both air and high pressure CO 2' The initial research programme was to investigate the microstructural changes which occurred with breakaway oxidation, a new EELS detector being cxi missioned to detenni. ne oxygen and raXbon levels. Oxidation in air was performed at temperatures between 500 and 1000'C. SEM and sane TEN cross sectional work was performed to determine the role of oxygen ingression, but prcblems in sample preparation made examination difficult. With cDcidation in high pressure OD2 the change from protective growth to breakaway is accanpanied by massive oxide growths usually at specimen corners. Microstructural changes also occur, with massive carbide growth acccrnpanying the changes in oxide structure. During oxidation, chemical exchanges between the oxidising gas, the metal and the inner oxide all contribute to the deposition of carbon at the metal/ oxide interface. This process generates internal stresses in the oxide, allowing microcracks to develop this enhancing the inward movement of the 002 and causing more, oxidation and carbon deposition. TEM cross sections were prepared to determine the mode of oxidation and the process by which carbon reaches the interface. In theory, EELS analysis allows identification of light elements Mi and above) but in practice the system proved very sample dependent, working well on thin films but very poorly on thick specimens (carbides). Evidence of the range of EELS mapping facilities are presented together with work on a new particle extraction system
42
Tappin, David Keith. "The characterisation of displacement cascades in austenitic Fe-Cr-Ni alloys." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317254.
Full text
43
Clauß, Arno Rainer. "Nitriding of Fe-Cr-Al alloys nitride precipitation and phase transformations /." Stuttgart : Max-Planck-Inst. für Metallforschung, 2008. http://d-nb.info/995395918/34.
Full text
44
Kjellqvist, Lina. "Thermodynamic description of the Fe-C-Cr-Mn-Ni-O system." Doctoral thesis, Stockholm : Skolan för industriell teknik och management, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11100.
Full text
45
KUNIOSHI, CLARICE T. "Obtencao e caracterizacao de ligas metalicas amorfas Fe-Cr-P eletrodepositadas." reponame:Repositório Institucional do IPEN, 1998. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10696.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:43:06Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:05:46Z (GMT). No. of bitstreams: 1 06210.pdf: 5391897 bytes, checksum: 31d1e55c71f38af31061fa75495c605f (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
46
Watson, Maxine. "Phase stability, constitution and precipitation effects in Fe-Ni-Cr alloys." Thesis, Sheffield Hallam University, 1990. http://shura.shu.ac.uk/20503/.
Full textAbstract:
A study of the constitution, transformation and precipitation effects in ternary Fe-Cr-Ni alloys and quaternary Fe-Cr-Ni-X alloys containing Mo, Nb, Ti, and Si was carried out. A systematic approach was adopted so that the microstructural effects observed as a result of ageing the selected iron base ternary alloys could be directly compared to the quaternary alloys. A series of ageing curves were plotted for the six ternary alloys over the temperature range 400°-900°C and for the ten quaternary alloys in the temperature range 650°-850°C. Optical and electron metallography were used to study the transformation and precipitation of intermetallic phases and carbides in the aged microstructures. The transformation of delta ferrite to sigma phase in a duplex (gamma+delta) ternary alloy was studied. The transformation was preceded by the precipitation of a cellular structure which formed on the delta/gamma grain boundaries and consisted of M23C6 and new austenite. A complex transformation product, which resembled a region of imiscibility, then formed at the delta/(gamma + M23C6) interface, this product consumed the delta ferrite grain, eventually transforming to sigma phase and new austenite. The alpha' phase, more commonly referred to as 475°C embrittlement, was also observed precipitating in the delta ferrite grains in two of the iron based ternary alloys in the temperature region 400°-500°C. Overageing of the alpha' precipitates after 1000 hours at 500°G was accompanied by the precipitation of a rod like austenite. The elements 2%Mo, 1%Nb, 1/4%Ti and 1% and 2%Si were added totwo Fe-Ni-Cr base alloys. One alloy was an austenitic (20Cr,23Ni) and the other was a transformable alloy (18Cr, 7Ni). The quaternary element additions had no effect on the constitution of the austenitic ternary alloy. However the addition of Mo to the 18Cr, 7Ni ternary alloy caused the transformation of delta ferrite to sigma phase over ageing temperature range 650°-850°C. The addition of Si moved the constitution of the ternary alloy further into the gamma+delta phase field, a small amount of sigma phase was observed in the 2%Si quaternary alloy on ageing at 650°C for 1000 hours. Irradiation damage studies were performed using High Voltage Electron Microscope and Variable Energy Cyclotron. The effect ofthe quaternary alloying additions Mo, Si, and Nb on the voidswelling behaviour of a 20Cr, 23Ni alloy were studied using 46MeV Ni6 ions in the Variable Energy Cyclotron, irradiating to a total dose of 10dpa at 550°C. All additions reduced void swelling, the largest reduction was observed in the Si containing allov. The Insert A Thermal ageing showed the presence of M23C6 the amount of which increased with increasing ageing temperature. No delta ferrite was observed in these alloys.
47
Dubois-Delmer, Catherine. "Solidification rapide d'aciers inoxydables Cr-Fe-Ni : effet de la composition." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0113.
Full textAbstract:
Nous avons applique la technique de solidification rapide de type melt-spinning a un alliage aisi 304 industriel et a des alliages de composition proche, legerement ferritiques, apres avoir montre que, dans les conditions d'equilibre donnees par le diagramme de phases du systeme cr-fe-ni, il devait se former de la ferrite primaire dans tous les cas. En tout premier lieu, nous avons constate une influence sensible de la teneur en chrome sur le comportement de l'alliage lors de sa mie en forme par contact avec le substrat (adherence, refroidissement secondaire, oxydation). Le resultat primordial a ete de constater l'apparition d'austenite primaire. Pour le fe-18cr-8ni et le fe-19cr-8ni, les vitesses de refroidissement etant relativement modestes, ce comportement a pu etre interprete par une extrapolation du diagramme etablissant la transition ferrite primaire/austenite primaire en fonction de la composition et de la vitesse du front de solidification, propose par bobadilla. Pour le fe-21cr-6ni, soumis a des vitesses de refroidissement beaucoup plus elevees et ne presentant pas de segregations, nous avons ete conduit a interpreter l'inversion du mode de solidification primaire par un effet de germination heterogene sur le substrat austenitique. Sur la base de la theorie classique de la germination heterogene polymorphe, nous avons pu etablir qu'il etait possible, dans certaines conditions, d'obtenir des germes austenitiques. Le calcul du rapport des frequences de germination qui nous a conduit a ce resultat ayant necessite une evaluation de l'energie libre interfaciale solide-liquide, nous avons ete amenes a etablir une extension du modele de becker au cas d'alliages multiconstitues se solidifiant de maniere polymorphe. En conclusion, nous avons evoque le possibilite d'etude plus approfondie de cette croissance eutectique couplee, induite par germination heterogene sur le substrat
48
Xu, Shuo. "A study of irradiation damage in iron and Fe-Cr alloys." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:fec4b2d0-411e-4c20-862d-e5fd884367f3.
Full textAbstract:
Irradiation damage structures induced in pure Fe and Fe-Cr (up to 14%Cr) alloys by 2 MeV Fe+ ion irradiations in the temperature range 300-460°C were investigated by transmission electron microscopy. Specimens were irradiated in bulk to doses of 1.5 x 1019 Fe+/m2 (about 2.5 displacements per atom: dpa) and 4.5 x 1019 Fe+/m2 (about 7 dpa). In most cases, damage took the form of dislocation loops with diameters from 2-100nm; the loops were distributed uniformly within all the samples. At higher irradiation temperatures (400°C, 460°C), complex microstructures such as finger loops (50nm in width and 1 micron in length) and perpendicular <100> loop clusters, were observed in both pure Fe and Fe-Cr samples. Loop sizes and densities were seen to change as a function of irradiation temperature and dose. Loop sizes were seen to increase as the increase of irradiation temperatures and doses, while loop densities only increased with increasing doses and decreased as increasing temperatures. Loops with both types of Burgers vectors (<100> and ½<111>) were observed in all the samples. The proportion of <100> loops was higher in Fe than that in Fe-Cr alloys at the same irradiation condition, which has can be attributed to the high mobility of ½<111> loops in Fe, so that a large proportion of them will escape to the (001) foil surface. A transition in loop Burgers vectors as a consequence of increasing temperature was observed. In Fe, the proportion of <100> loops increased with increasing irradiation temperature from 40% at 300°C to 60% at 460°C. A similar trend was found in the Fe-Cr alloys, but due to the higher proportion of ½<111> loops in these alloys, the increase of <100> loops was not that obvious, being from 30% at 300°C to 45% at 460°C(Fe-11Cr). The effects of irradiation dose rate on the formation of dislocation loops by 2 MeV Fe+ ions were also investigated. These irradiations were carried out at 300°C with two different implantation dose rates: 6 x 10-4 dpa/s and 3 x 10-5 dpa/s. The implantation dose for both implantations was 0.38 x 1019 Fe+/m2 (0.5 dpa). Both the average loop size and loop densities for the Fe-Cr specimens subjected to the high dose rate irradiation were higher than that in the low dose rate irradiations. Take Fe-14Cr as an example, that the loop densities in high dose rate irradiation increased about 90% compared to that in low dose rate, and the average loop size in high dose rate irradiation was 30% larger than that in low dose rate irradiation. The ‘inside-outside contrast’ method was applied to determine the loop nature in all the samples. It was found that all the large loops (>5nm) are of interstitial type. Any vacancies are believed to exist in the form of small dislocation loops (<5nm) or sub-microscopic voids.
49
Ginter, Caroline. "Influence des éléments d'alliage sur les mécanismes de nano-précipitation et sur les mécanismes de durcissement d'alliages modèles (Fe-Cr et Fe-Cr-C) et d'aciers industriels nitrurés." Vandoeuvre-les-Nancy, INPL, 2006. http://docnum.univ-lorraine.fr/public/INPL/2006_GINTER_C.pdf.
Full textAbstract:
Ce travail s'inscrit dans un contexte de haute technologie. Il concerne le comportement des aciers alliés, nitrurés par voie gazeuse à 520°C, en matière de mécanismes de nano-précipitation et leur incidence sur le durcissement. La caractérisation des précipités nanométriques a été réalisée par METHR et nano-sonde EDX, complétée par les calculs thermodynamiques de phases, à l'aide du logiciel Thermo-Calc. L'étude réalisée sur des alliages binaires (Fe-Cr) et ternaires (Fe-Cr-C) nitrurés, a permis de proposer une nouvelle explication concernant l'excès d'azote : la précipitation de nitrures mixtes (Fe,Cr)N. Les rôles du chrome et de la microstructure initiale sur le durcissement ont également été déterminés et les mécanismes de précipitation expliqués. Les investigations entreprises sur une dizaine d'aciers industriels nitrurés ont confirmé que le chrome et l'aluminium sont les éléments d'alliage les plus influents sur le durcissement. La caractérisation des aciers industriels 32CrMoV13 et 30CrAlMo6. 12 a mené à l'identification du rôle de ces deux éléments et de la microstructure initiale, sur les mécanismes de précipitation, et leur impact sur le durcissement. L'excès d'azote, mis en évidence systématiquement sous la surface, est lié à la précipitation de nitrures mixtes (Fe,Cr,Al,Mo,Mn,V)N et de nitrures de fer, en présence d'Al. Il a été démontré que les plaquettes nanométriques MN sont essentiellement responsables du durcissement. En ce qui concerne les applications industrielles, cette étude a conduit à l'optimisation de la composition des aciers industriels de nitruration, afin de réduire les cycles thermochimiques, tout en conservant les propriétés mécaniquesThis work deals with high tech industries. It concerns the behavior of gas-nitrided (520°C) alloyed steels, in terms of nano-precipitation mechanisms, with incidence on hardening. Nano-precipitates characterization was performed by HRTEM and nano-probe EDX, complemented by thermodynamic phases calculations, with the help of Thermo-Calc software. The study carried out on nitrided binary (Fe-Cr) and ternary (Fe-Cr-C) alloys, allowed to propose a new explanation about nitrogen excess: nitrides (Fe,Cr)N precipitation. Chromium and initial microstructure effects on hardening were determined, and precipitation mechanisms explained. Investigations conducted on about 10 nitrided industrial steels, confirmed that chromium and aluminium are the most influent alloying elements on hardening. The 32CrMoV13 and 30CrAlMo6. 12 industrial steels characterization resulted in identifying the role of those elements and the one of initial microstructure on precipitation mechanisms, and their impact on hardening. Nitrogen excess, systematically pointed out above the surface, is related to (Fe,Cr,Al,Mo,Mn,V)N mixed nitrides and iron nitrides (in presence of Al) precipitation. It was demonstrated that nanometric platelets MN are mainly responsible for hardening. Concerning industrial application, this study led to optimize the nitrided industrial steels composition, in order to reduce thermochemical cycles, while keeping mechanical properties
50
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