Étude des modifications microstructurales de superalliages à base nickel induites par nitruration assistée plasma PDF Download

Author: Sébastien Chollet
Publisher:
ISBN:
Category :
Languages : fr
Pages : 0

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Book Description
Les turbines aéronautiques et terrestres utilisent comme matériaux de structure les superalliages à base nickel. Ils sont confrontés en utilisation à des environnements agressifs à très hautes températures, conduisant à l'usure et la corrosion, et à des sollicitations mécaniques qui entraînent fatigue et fluage. Pour permettre l'utilisation de ces matériaux dans des conditions toujours plus sévères de fonctionnement et augmenter la durée de vie des pièces, divers traitements de nitruration ont été proposés pour durcir la surface tout en conservant ou en améliorant la tenue mécanique et la résistance chimique. Les modifications induites par la nitruration, leur stabilité et l'influence de la microstructure initiale sont encore mal comprises dans ces matériaux complexes. Au cours de ces travaux, nous avons étudié les effets d'une nitruration assistée plasma en fonction de la microstructure et de la composition chimique des alliages. Différents types de superalliages à base nickel ont été choisis, de microstructures variées, comprenant éventuellement des précipités de type Ni3(Al,Ti,Nb) et/ou Ni3 (Nb). Nous avons alors caractérisé les modifications induites par l'introduction de l'azote dans les matériaux suite à un traitement de nitruration à basse température (400°C) : expansion de la maille, génération de contraintes résiduelles, comportement des précipités, formation de nitrures, plasticité, anisotropies... Les résultats obtenus suggèrent des effets différents selon la composition des précipités. Ces modifications structurales et leurs évolutions ont ensuite été étudiées lors d'un recuit à plus haute température (650°C) afin d'étudier la stabilité des couches formées.

Author: Agnes Buka
Publisher: World Scientific
ISBN: 1848167997
Category : Science
Languages : en
Pages : 299

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The book intends to give a state-of-the-art overview of flexoelectricity, a linear physical coupling between mechanical (orientational) deformations and electric polarization, which is specific to systems with orientational order, such as liquid crystals. Chapters written by experts in the field shed light on theoretical as well as experimental aspects of research carried out since the discovery of flexoelectricity. Besides a common macroscopic (continuum) description the microscopic theory of flexoelectricity is also addressed. Electro-optic effects due to or modified by flexoelectricity as well as various (direct and indirect) measurement methods are discussed. Special emphasis is given to the role of flexoelectricity in pattern-forming instabilities. While the main focus of the book lies in flexoelectricity in nematic liquid crystals, peculiarities of other mesophases (bent-core systems, cholesterics, and smectics) are also reviewed. Flexoelectricity has relevance to biological (living) systems and can also offer possibilities for technical applications. The basics of these two interdisciplinary fields are also summarized.

Author:
Publisher:
ISBN: 9781617827709
Category : Electronic books
Languages : en
Pages :

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Author: W Sha
Publisher: Elsevier
ISBN: 1845695860
Category : Technology & Engineering
Languages : en
Pages : 588

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Given their growing importance in the aerospace, automotive, sports and medical sectors, modelling the microstructure and properties of titanium and its alloys is a vital part of research into the development of new applications. This is the first time a book has been dedicated to modelling techniques for titanium.Part one discusses experimental techniques such as microscopy, synchrotron radiation X-ray diffraction and differential scanning calorimetry. Part two reviews physical modelling methods including thermodynamic modelling, the Johnson-Mehl-Avrami method, finite element modelling, the phase-field method, the cellular automata method, crystallographic and fracture behaviour of titanium aluminide and atomistic simulations of interfaces and dislocations relevant to TiAl. Part three covers neural network models and Part four examines surface engineering products. These include surface nitriding: phase composition, microstructure, mechanical properties, morphology and corrosion; nitriding: modelling of hardness profiles and kinetics; and aluminising: fabrication of Ti coatings by mechanical alloying.With its distinguished authors, Titanium alloys: Modelling of microstructure, properties and applications is a standard reference for industry and researchers concerned with titanium modelling, as well as users of titanium, titanium alloys and titanium aluminide in the aerospace, automotive, sports and medical implant sectors. - Comprehensively assesses modelling techniques for titanium, including experimental techniques such as microscopy and differential scanning calorimetry - Reviews physical modelling methods including thermodynamic modelling and finite element modelling - Examines surface engineering products with specific chapters focused on surface nitriding and aluminising

Author: Jerome V. Moloney
Publisher: Springer Science & Business Media
ISBN: 9780387985817
Category : Business & Economics
Languages : en
Pages : 270

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Mathematical methods play a significant role in the rapidly growing field of nonlinear optical materials. This volume discusses a number of successful or promising contributions. The overall theme of this volume is twofold: (1) the challenges faced in computing and optimizing nonlinear optical material properties; and (2) the exploitation of these properties in important areas of application. These include the design of optical amplifiers and lasers, as well as novel optical switches. Research topics in this volume include how to exploit the magnetooptic effect, how to work with the nonlinear optical response of materials, how to predict laser-induced breakdown in efficient optical devices, and how to handle electron cloud distortion in femtosecond processes.

Author: Luz Stella Gomez-Villalba
Publisher: Trans Tech Publications Ltd
ISBN: 3035733201
Category : Technology & Engineering
Languages : en
Pages : 168

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This volume presents the recent research progress in the synthesis, characterization techniques, properties and interactions of nanostructured materials for multifunctional applications. The opportunity to apply singular or hybrid nanomaterials proves to be a constant challenge in order to optimize its use, achieving simultaneous results for its application in different branches of research. It is focused on the study of structures and their effect on the properties of solids, using different experimental techniques and practical applications of nanostructured materials in the context of the latest achievements in the area of research of solid-state phenomena.