Ce travail s’intéresse à la formulation et à la caractérisation de mortiers cimentaires imprimables en 3D. Il a été réalisé dans le cadre du projet MATRICE cofinancé par le fonds Feder et la région Hauts de France. Un cahier des charges pour un matériau cimentaire imprimable est tout d’abord défini sur la base de trois critères : l’extrudabilité, la constructibilité et la conservation des résistances mécaniques sur matériau imprimé. Deux mortiers imprimables sont formulés en utilisant des essais simples à l’échelle du laboratoire. Le premier mortier, à prise lente, est composé d’un liant à base de ciment Portland (OPC). Le second mortier, à prise accélérée, est composé d’un liant mixte (93 % d’OPC et 7 % de ciment sulfoalumineux (CSA)). Des impressions à l’échelle réelle sont ensuite réalisées dans le cadre du projet MATRICE et permettent de valider leur imprimabilité selon l’application de chacun. Le comportement chimique de mélanges de ciment Portland et de ciment sulfoalumineux est ensuite étudié expérimentalement. Les chaleurs d’hydratation mesurées par calorimétrie isotherme augmentent avec le dosage en CSA (de 2 % jusqu’à 10 %) et sont plus élevées que celles des pâtes de ciment contenant 100 % d’OPC et 100 % de CSA. La comparaison des hydrates identifiés dans le mélange à 7 % de CSA à ceux présents dans les deux pâtes de ciment pures montre que la présence de gypse et de chaux provenant du ciment Portland entraîne une hydratation plus rapide de la ye’elimite provenant du CSA et une formation d’ettringite à très court terme. Par contre, la nature des hydrates du ciment Portland n’est pas affectée. Le comportement rhéologique, notamment, la thixotropie, de pâtes constituées de mélanges de ciment Portland et sulfoalumineux (jusqu’à 10 %) est ensuite étudié en fonction de différents paramètres de formulation pendant la première heure. L’augmentation du dosage en CSA (0 % à 10 %) entraîne une augmentation quasi linéaire du coefficient de structuration (Athix) de ces mélanges. Pour les mélanges à 7 % de CSA et 100 % d’OPC, l’influence du rapport E/C et du dosage en superplastifiant sur la thixotropie est ensuite étudiée. L’augmentation du rapport E/C entraîne une diminution quasi linéaire de Athix pour chacune des pâtes de ciment. En revanche, le superplastifiant présente une faible influence comparativement au rapport E/C. / The interest of this study is the formulation and characterization of 3D printing cementitious mortars. This research work has been carried out in the frame of the MATRICE Project, co-funded by the region “Hauts de France” and the European Union with the European Regional Development Fund. Specifications for a cementitious printable material are first set based on three criteria: extrudability, buildability and conserving the compressive strength of the printed material. Two printable mortars are formulated using simple tests on a laboratory scale. The first, with slow setting, is composed of a Portland-based binder (OPC). The second, with accelerated setting, is composed of a mixed binder (93% OPC and 7% sulfoaluminous cement (CSA)). Real scale prints are then realized in the frame of the project MATRICE allowing the validation of the printability of each mortar upon its application. The chemical behavior of Portland cement and sulfoaluminate cement mixes is then studied experimentally. The heats of hydration measured by isothermal calorimetry increase with the CSA dosage (2% to 10%) and are higher than those of cement pastes containing 100% OPC and 100% CSA. The comparison of the hydrates identified in the mix mad of 7% CSA to those present in the two other cement pastes of each cement alone shows that the presence of gypsum and lime from the Portland cement lead to a faster hydration of the ye’elimite from CSA and to an early formation of ettringite. However, the nature of hydrates is not affected. The rheological behavior, in particular the thixotropy, of the cement pastes made of Portland cement and sulfoaluminate cement (up to 10%) is then studied in function of different formulation parameters during the first hour. The increase in CSA dosage (0% to 10%) leads to an almost linear increase of the structuration coefficient (Athix) of theses mixes. For mixes with 7% CSA and 100% OPC, the influence of the W/C ratio and superplasticizer on the thixotropy is then studied. The increase in W/C ratio leads to an almost linear decrease of the Athix for each of cement paste. However, the superplasticizer present a low influence compared to the W/C ratio.

The complex interaction between cement and chemical/mineral admixtures in concrete mixtures sometimes leads to unpredictable concrete performance in the field which is generally defined as concrete incompatibilities. Cement paste rheology measurements instead of traditional workability tests (i.e., slump cone test) can have great potential in detecting those incompatibilities in concrete before the concrete is placed, which can, in turn, avoid related workability problems and setting time as well as heat evolution abnormalities. The objectives of the present study were to examine the applicability of the dynamic shear rheometer (DSR) to measure cement paste rheology, and to identify cement and mineral/chemical admixture incompatibilities, based on the determined rheological parameters. The DSR was modified and optimized for cement paste rheology measurements. Two different modes of operations (i.e., static and dynamic methods) with the modified DSR were investigated to measure representative rheological parameters as well as to identify cement and chemical/mineral admixture incompatibility. The conventional plastic viscosity and yield stress are measured in static mode and storage modulus curve, as a function of time, is measured in dynamic mode. The rate of change of plastic viscosity (RPV) as another static rheological parameter and the modeled magnitude parameter ?, from the dynamic rheological method, showed great potentialities as acceptance criteria to identify incompatible mixtures. The heat of hydration data from isothermal conduction calorimeter tests and setting time results for the studied mixtures have strongly supported the rheology based observations as supporting tools. Based on the main tests results, the acceptance criteria were set up using the rheological parameters in accordance with heat of hydration data. This will ultimately help material suppliers, concrete producers, and other users to detect problematic combinations of concrete ingredients before a given concrete mixture is placed.

[pt] Operações de posicionamento de tampão de cimento na indústria do petróleo representam um exemplo de escoamento dominado por efeitos gravitacionais. Essa situação é altamente instável visto que o cimento geralmente é mais denso que o fluido do poço e, como consequência, suas posições tendem a se inverterem. O presente estudo objetiva aprimorar a percepção dos mecanismos físicos associados às operações de tamponamento através da análise de escoamentos de inversão por gravidade. Com esta finalidade, executam-se experimentos de visualização com líquido mais denso posicionado sobre outro de menor densidade em tubo vertical. Ademais determina-se a velocidade da interface através do processamento e análise de imagens. A influência dos parâmetros governantes é averiguada sobre a velocidade de inversão e o regime de escoamento. A importância relativa entre as forças gravitacionais, viscosa, inercial e interfacial são avaliadas. A primeira etapa do estudo consiste na realização de experimentos com pares de fluidos newtonianos e imiscíveis com pequena diferença de densidade. Examinam-se dois regimes de escoamento, a saber gotas e slugs em queda. Os resultados experimentais demonstram que a velocidade terminal pode ser estimada por correlações empíricas de esferas rígidas em queda dentro de um tubo. A segunda etapa da pesquisa consiste na análise de escoamento de inversão por gravidade com fluido elasto viscoplástico tixotrópico sobre óleo newtoniano menos denso. Constatam-se três diferentes regimes de escoamento, denominados instável, quase-estável e estável (sem escoamento). O regime instável apresenta escoamento wavy core annular com o líquido mais denso no centro. No regime quase-estável há formação de plug flow após um tempo de retardo, que é função dos efeitos tixotrópicos e elásticos do material. Através da análise dos resultados experimentais é possível identificar, para um dado par de fluidos, a janela de operações no espaço de parâmetros governantes dentro da qual a velocidade de inversão é suficientemente baixa (ou nula) para assegurar o sucesso da operação de tamponamento. / [en] Cement plug placement in oil industry operations represents an example of buoyancy-driven exchange flows. This situation is highly unstable since cement is usually denser than well fluid and, as a consequence, their positions tend to invert. The present study aims to improve the perception of the physical mechanisms associated to cement plug operations through the analysis of exchange flows. To this end, visualization experiments are performed with denser liquid positioned above a lower-density liquid in a vertical tube. In addition, the interface front speed is determined through image processing and analysis. The influence of the governing parameters is investigated on the speed of inversion and flow regime. The first stage of the study consists of conducting experiments with pairs of immiscible Newtonian liquids with small density difference. Two different flow regimes were examined, namely, falling drops and falling slugs. Experimental results demonstrate that the terminal velocity can be estimated by empirical correlations for falling rigid spheres within a tube. The second stage of the research consists of an exchange flow analysis considering an elastoviscoplastic thixotropic fluid above a less dense Newtonian oil. Three different flow regimes were observed, namely unstable, quasi-stable, and stable (no flow). The unstable regime is a wavy core-annular flow with the denser liquid in the core. In the quasi-stable regime a slow plug flow starts after a time delay, which is a function of material thixotropic and elastic effects. Through analysis of the experimental results it is possible to identify, for a given pair of fluids, the operational window in the governing parameter space within which the speed of inversion is sufficiently low (or zero) to ensure the cement plug operation success.

Orientador: Geraldo de Freitas Maciel / Resumo: O ensaio de abatimento de tronco de cone, desenvolvido inicialmente como ferramenta de controle de qualidade para avaliar a consistência de materiais cimentícios e com grande aplicação no setor da construção civil, tem sido cada vez mais empregado para análise de materiais de diferentes setores, seja da indústria do petróleo, da mineração e mesmo de alimentos. O interesse de diferentes setores industriais pela medida do abatimento deve-se a esta possibilitar uma ferramenta de controle de qualidade de materiais e ainda fornecer um mecanismo simples e fácil para a determinação de um importante parâmetro reológico, a tensão limite de escoamento. Nesse contexto, esta dissertação de mestrado apresenta o desenvolvimento de um aparato experimental capaz de realizar, de forma automatizada, o ensaio de abatimento de tronco de cone (comumente conhecido por slump test), desde o levantamento do cone de Abrams até a medição do abatimento. A partir do equipamento desenvolvido, três abordagens são realizadas e discutidas ao longo desta dissertação, tendo como materiais avaliados os géis de carbopol (fluido teste reologicamente representativo de lamas), lamas, argamassas e concretos. A primeira abordagem diz respeito a funcionalidade e operacionalidade do aparato automatizado de slump test. A segunda abordagem apresenta modelos empíricos de determinação da tensão limite de escoamento e viscosidade aparente, a partir da medida mais rigorosa de abatimento e outras informações fornecidas pelo a... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The slump test was, initially, developed as a quality control tool for evaluating the consistency of cement-based materials, with many applications in civil engineering, it has been used for the analysis of materials in different sections of petrol industries, mining, and even food industries. The interest of these different industrial sections in the slump is due to its possible role as quality control tool of materials, providing an easy and simple mechanism for the determination of an important rheological parameter: the yield stress. In this context, this dissertation presents the development of an experimental apparatus capable of obtaining, in such automated way, the slump test, since the lifting of the Abrams cone to the obtaining of the slump. From the apparatus, three approaches are presented and discussed in this text, showing the results for the evaluation of materials such as carbopol gel (a rheological representative fluid of mud), mud, concrete and mortar. The first approach deals with the functionality of the automated apparatus for slump test. The second approach presents empiric models for the determination of yield stress and apparent viscosity, from the slump and further information obtained by the automated apparatus. The third and last approach presents the numerical simulation and validation of the slump test by the use of FLUENT software, considering the Non-Newtonian property (Herschel-Bulkley’s fluid) of the tested materials, and the trial of the mode... (Complete abstract click electronic access below) / Mestre

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2015-05-08T14:05:16Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) 1 Dissertação - João Vitor Nogueir.pdf: 7740367 bytes, checksum: e311056ecafb8741fc3538682907dcc1 (MD5) / Made available in DSpace on 2015-05-08T14:05:16Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) 1 Dissertação - João Vitor Nogueir.pdf: 7740367 bytes, checksum: e311056ecafb8741fc3538682907dcc1 (MD5) Previous issue date: 2014-01-30 / A instabilidade de Saffman-Taylor se dá na interface entre dois fluidos viscosos no interior de uma célula de Hele-Shaw (CHS). A CHS é um aparato experimental que consiste em duas placas, usualmente planas e paralelas, separadas por uma distância muito pequena. Sabe-se que quando um fluido viscoso desloca outro mais viscoso, em uma CHS, a interface entre eles se torna instável e estruturas chamadas de “dedos viscosos” surgem. Em função da geometria da CHS e da força motriz do fluxo, tais dedos podem bifurcar, afinar, competir em tamanho e interferirem uns com os outros, formando as mais diversas estruturas morfológicas. Estudos com fluidos newtonianos em CHS vêm sendo feitos desde o final do século XIX. No entanto, apenas recentemente, a cerca de trinta anos, estudos com fluidos não newtonianos em CHS vêm sendo conduzidos, e em sua maioria estudos analíticos lineares ou não lineares puramente numéricos. Este trabalho tenta preencher essa lacuna com um estudo analítico não linear de fluidos não newtonianos em CHS. Estudamos a CHS de geometria radial com levantamento da placa superior e injeção como forças motrizes do fluxo. Nestes casos estudamos o fluido yield stress, um tipo especial de fluido não newtoniano que se comporta como um “semissólido”. Estudamos também o fluido power-law que introduz, na viscosidade, uma dependência do fluxo. Em cada caso fomos capazes de estabelecer conexões entre as nossas previsões teóricas e os experimentos e simulações encontrados na literatura. Tais previsões são acerca da estabilidade e morfologia da interface como: bifurcação de dedos, a estrutura conhecida como side branching e a competição entre dedos.

Les phénomènes de mouillage et la rhéologie des fluides à seuil sont deux domaines de la physique des matériaux mous dans lesquels de grandes avancées ont été faites lors des derniers siècles. De plus ces questions sont d'une grande importance au niveau des applications industrielles, ce qui contribue à leur dynamisme. En revanche, le mouillage des fluides à seuil a été peu étudié, alors que c'est une situation fréquente. En effet, presque tous les fluides rencontrés dans l'industrie et la vie quotidienne sont des fluides à seuil. D'autre part, la connaissance des propriétés de mouillage est cruciale lors de leur manipulation car la plupart des processus font intervenir des interfaces.Dans ma thèse, je m'intéresse aux questions suivantes : comment la tension de surface apparente est-elle affectée par le seuil ? Comment le seuil influence-t-il la dynamique du mouillage, habituellement décrite par la loi de Tanner ? Pourquoi l'angle de contact d'une goutte de fluide à seuil n'est-il pas prédit par la loi d'Young-Dupré ?J'ai réalisé des expériences sur un fluide à seuil modèle appelé carbopol. La première expérience a consisté à mesurer la force d'adhésion d'un pont capillaire, qui a été comparée au cas des fluides simples. Les résultats ont montré l'importance de l'histoire de la déformation et de l'élasticité du fluide. La seconde expérience a porté sur l'étalement de gouttes sur une surface hydrophile. J'ai étudié la dynamique d'étalement, ainsi que l'angle de contact final. Alors que la dynamique est contrôlée par la viscoélasticité, l'état final est déterminé par le seuil / Wetting phenomena and yield-stress fluids rheology are subfields of soft matter physics where big understanding steps have been made during the last centuries. In addition, these two fields have very important potential implications for industry, which contributes to their dynamism. But their combination, the wetting of yield-stress fluids, has received little interest until the very last years, although it is a situation that happens all the time. Indeed, yield-stress fluids gather nearly all the fluids encountered in food industry, cosmetics, building industry, oil and gas industry… and wetting properties are crucial when processing or using the fluids, as many processes involve interfaces with air or a solid surface.In this thesis, I consider the following questions: how is the apparent surface tension affected by yield stress? How does the yield stress influence the wetting dynamics, classically described by Tanner’s law? Why can the final contact angle of a sessile drop of yield-stress fluid not be predicted by Young-Dupré’s theory?I performed experiments with a model yield-stress fluid called carbopol. The first experiment consisted in measuring the adhesion force of a capillary bridge and comparing it to the case of simple fluids. The main results show the importance of the deformation history and of the fluid elasticity. The second main experiment concerned spreading of drops on a hydrophilic surface. I studied the short-time dynamics and the long-time dynamics, as well as the final contact angle. The first regime is controlled by viscoelasticity, whereas the final state is determined by the yield stress

Nous étudions la formation de bulles dans un fluide à seuil (matériaux liquides si la contrainte appliquée est supérieure à la contrainte seuil, et solides autrement) au moyen de géométries milli fluidiques (jonctions en T, “flow focusing“) constituées de canaux axisymétriques, et fabriquées par stéréo lithographie. En tirant partie de la domination des effets capillaires par la contrainte seuil, nous produisons des bulles dans des fluides à seuil simples (émulsions concentrées, gels de carbopol). La formation des bulles est due au pincement du filament de gaz par l'écoulement de fluide à seuil à débit imposé. Il rappelle celui observé pour des fluides Newtoniens dans des géométries de “flow focusing“ 2D. Nous étudions les différents régimes de fonctionnement de ces systèmes lorsque le débit de fluide à seuil et la pression de gaz sont imposés. La production instationnaire de bulles est observée, et expliquée par la rétroaction provenant des variations de résistance hydrodynamique induites par la formation des bulles sur le débit de gaz. La déstabilisation finale se produit lorsque toutes les bulles coalescent. Ceci est dû au transfert de fluides entre les ponts liquides séparant les bulles et les films fins situés près des parois solides. Aussi, nous étudions le dépôt de fluide à seuil dans un tube capillaire avec ou sans glissement aux parois. En effet, ce phénomène est courant lors de l'écoulement de fluide à seuil en milieu confiné sur des surfaces lisses. Les résultats peuvent être décrits par une loi d'échelle (contrainte interne équilibrant le gradient de pression capillaire) lorsqu'il n'y a pas de glissement aux parois. Dans le cas contraire nous montrons qu'il existe trois régimes dépendant de l'état de contrainte du système, et qu'ils fixent les formes de bulle observées en régime instationnaire. Finalement, différentes méthodes de régulations (pression, écoulement pulsés) nous permettent d'obtenir des régimes stationnaires. Ceux-ci sont caractérisés (fraction volumique de gaz, temps de formation de bulles), et permettent l'obtention de mousses de fluides à seuil. Ainsi, ouvrant potentiellement la voie à la production contrôlée de fluides à seuil aérés à grande échelle / We study the formation of bubbles inside yield stress fluids (liquid when the applied stress is above the yield stress, and solid otherwise) using mill fluidic geometries (T-junctions, flow focusing devices) made of axisymmetric channels, and manufactured by stereo lithography. We show that dispersing bubbles in simple yield stress fluids (concentrated emulsions, and carbopol gels) is possible by taking advantage of the yield stress over the capillary stress, and due to the squeezing of the gas thread by the core of the yield stress fluid flow at imposed flow rate. The observed behaviour is reminiscent of the geometrical operating regime in 2D flow-focusing devices for Newtonian fluids. We investigate the different operating regimes that occur when the yield stress fluid flow rate and the gas pressure are imposed. We report that, for these inlet conditions the production is unsteady, which comes from the hydrodynamic feedback induced by the formation of each bubble on the gas flow rate. The regime eventually breaks down when all bubbles coalesce. This is due to the transfer between the liquid plugs separating each bubble and the thin film located on the channel wall. Thus, we study the deposition of yield stress fluid on the wall of capillary tubes. Indeed, this often occurs for yield stress fluids flowing in confined geometries on smooth surfaces. The results with no-slip are well described by a classical scaling law (internal stresses balanced by capillary pressure gradient). When there is wall slip, we show that there are three regimes that depend on the stress state of the system, and set the bubbles' shape observed for unsteady regimes. Finally, different regulation methods (pressure, pulsated flows) allow to obtain steady regimes. They are characterized (gas volume fraction, bubble formation time) and we show that they allow to obtain yield stress fluid foams. Thus, identifying pathways for potential steady-state controlled production of aerated yield stress fluids at large scale

Les fluides à seuil sont des matériaux utilisés dans de nombreux procédés industriels au cours desquels ils sont mis en écoulement via leur interaction avec des outils solides. Afin de mieux comprendre comment ils s'étalent sur des surfaces, nous avons étudié d'une part leur enduction verticale sur une plaque mince et d'autre part leur étalement horizontal à l'aide d'une lame. Ces deux études se sont appuyées sur des mesures macroscopiques permettant de suivre la force appliquée à l'outil et des mesures microscopiques de PIV pour déterminer les champs de vitesse dans le matériau. Après confirmation de leur validité par comparaison avec nos résultats expérimentaux, des simulations numériques basées sur la programmation conique ont permis de préciser les écoulements en jeu. Pour l'enduction par trempage, nous observons que dans notre gamme d'étude, le dépôt de fluide à seuil sur la plaque est millimétrique et d'épaisseur constante, sauf aux extrémités. Selon le rapport des forces visqueuses et plastiques, l'enduction est régie par un équilibre "seuillo-gravitaire" ou "visco-gravitaire". Nous avons ensuite caractérisé l'écoulement généré dans le bain par le déplacement de la plaque afin d'expliciter l'origine du phénomène d'enduction. Les simulations numériques précisent la forme de cet écoulement. L'étalement horizontal dans un canal à l'aide d'une lame mince conduit au déplacement d'un amas de fluide faiblement cisaillé par rapport à une région de fluide au repos, par l'intermédiaire d'une couche cisaillée. Nous montrons qu'un modèle simple permet de prédire la dynamique de croissance de l'amas et la relie à la force normale à la lame / Yield stress fluids are used in various industrial processes in which solid tools make them flow. To have a better understanding on how they spread on surfaces, we first studied the vertical coating on a thin plate and then the horizontal blade-coating. Both studies are based on macroscopic measures recording the force applied on the plate and on the microscopic determination on the velocity fields in the fluid by PIV. Numerical simulations based on cone programming, which validity had been confirmed in comparison to our experimental results, specified the flows at stake. In dip-coating, we observed than within our framework, the yield stress fluid deposit on the plate is millimetric and of constant thickness, except on the tips. According to the value of the viscous over plastic forces ratio, the coating is led by a "yield-gravity" or a "visco-gravity" balance. Then, we characterized the flow generated in the bath by the plate displacement in order to clarify the origin of the coating phenomenon. The numerical simulations specified the flow characteristics. The horizontal blade-coating in a channel involves the displacement of a weakly sheared cluster of fluid in relation to a part of fluid at rest, through a sheared layer. We showed that the growing dynamic of the cluster is described with a simple model which links it to the normal force to the plate

La relation scalaire entre contrainte et déformation obtenue par le cisaillement simple dans les rhéomètres classiques n'est pas assez riche pour décrire les écoulements complexes. Pour obtenir plus d'information, nous superposons deux écoulements orthogonaux en utilisant la géométrie plan-plan. Le fluide, sous forme cylindrique, peut alors être cisaillé par la rotation mais aussi écrasé par le rapprochement (ou étiré par l'éloignement) des disques. Nous détaillons les calculs théoriques permettant de déterminer les liens entre contraintes et taux de cisaillement et les efforts et vitesses macroscopiques associés. Ensuite, nous décrivons précisément le dispositif expérimental mis en place pour imposer toutes sortes d'écoulements combinant des cisaillements stationnaires ou oscillants, en rotation ou en écrasement. Puis nous présentons les résultats de la comparaison entre l'écoulement de rotation et l'écoulement d'écrasement. Nous présentons enfin les expériences de superposition des deux écoulements. Nous créons des écoulements complexes et divers afin, entre autres, de mesurer et comprendre la loi d'écoulement 3D et le critère d'écoulement 3D des fluides à seuil / The scalar relation between stress and strain obtained by simple shear within classical rheometers is not rich enough to describe complex flows. To obtain more information, we shall superimpose two orthogonal flows and for that, we shall use the parallel-plate geometry. The volume of fluid has a cylindrical shape and can be sheared by the rotation of a plate or squeezed by the move closer (or stretched by the move away) of the plates. We detail theoretical considerations that allow us to determine the link between stresses and shear rates and associated macroscopic efforts and velocities. Then we precisely describe the experimental setup developed to impose all kind of flows : steady or oscillating flows, rotation or squeeze. After that, we present the results of comparison between rotational and squeeze flow. Finally, we present the experiments with both superimposed flows. We create complex flows to measure and understand, among others, 3D behavior and 3D flow criteria of yield stress fluids

Oxygen strengthened biomedical beta titanium alloys Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt. %) exhibits a low Young's modulus and high strength thanks to interstitial strengthening effect of oxygen. These mechanical properties are promising for implant production. In this thesis, the aforementioned alloy is thoroughly studied in conditions prepared by various thermomechanical treatments, namely: material after casting, hot compression testing, die-forging, hot rolling and finally, cold-swaged and annealed condition. Mechanical properties and microstructure of prepared conditions are studied with special interest of enhancing the fatigue performance that is poor after casting due to porosity and large grains. The hot rolling was shown to improve the fatigue performance significantly, mainly through grain refinement. It is shown that by combining the effects of cold-swaging and recrystallization annealing, extensive refinement of grain structure can be achieved. Industrial aspects of implant production by the studied methods were discussed. In the second part of the thesis, the possibility of lowering the Young's modulus by reducing the beta phase stability (by reducing of Nb and Ta content), while retaining high strength caused by high interstitial oxyen content is explored. Several alloys were...