Despite of their costs, titanium alloys are often used for structural applications due to their high performance to density ratio that allows the manufacturers to reach the aimed mechanical properties. Users are more and more inclined to turn towards the ƓÒ-metastable alloys since they provide a wider range of processing conditions, very attractive corrosion resistance and higher strength levels in comparison to the ƓÑƓyƓÒ alloys. Nevertheless, these alloys present a high sensitivity to the variation in the applied heat- or thermomechanical treatment influencing the final mechanical properties. That is why the understanding of the relationships existing between these heat- or thermomechanical treatments and the corresponding modifications of the microstructures, as well as the influence of several characteristics of the microstructure on the mechanical properties under static and cycling loading conditions is of primary importance. This research allows to characterise and to better understand the precipitation and growth sequences of the ƓÑ phase in the Ti-LCB alloy during classical heat- and thermomechanical treatments in order to be able to predict the microstructure resulting from a defined treatment. Furthermore, to improve the understanding of the relationships existing between the manufacturing process, the corresponding microstructures modifications, and the mechanical properties, tensile tests are performed on the different microstructures and microstructural parameters playing an important role on the static properties are identified. Microstructural features governing the static fracture process in two different microstructures are determined by using a micromechanical model based on a physical understanding of the mechanisms of damage. Finally, the crack initiation and the first stage of crack propagation under high cycle fatigue conditions are investigated at a local scale on two different microstructures.

Despite of their costs, titanium alloys are often used for structural applications due to their high performance to density ratio that allows the manufacturers to reach the aimed mechanical properties. Users are more and more inclined to turn towards the ƓÒ-metastable alloys since they provide a wider range of processing conditions, very attractive corrosion resistance and higher strength levels in comparison to the ƓÑƓyƓÒ alloys. Nevertheless, these alloys present a high sensitivity to the variation in the applied heat- or thermomechanical treatment influencing the final mechanical properties. That is why the understanding of the relationships existing between these heat- or thermomechanical treatments and the corresponding modifications of the microstructures, as well as the influence of several characteristics of the microstructure on the mechanical properties under static and cycling loading conditions is of primary importance. This research allows to characterise and to better understand the precipitation and growth sequences of the ƓÑ phase in the Ti-LCB alloy during classical heat- and thermomechanical treatments in order to be able to predict the microstructure resulting from a defined treatment. Furthermore, to improve the understanding of the relationships existing between the manufacturing process, the corresponding microstructures modifications, and the mechanical properties, tensile tests are performed on the different microstructures and microstructural parameters playing an important role on the static properties are identified. Microstructural features governing the static fracture process in two different microstructures are determined by using a micromechanical model based on a physical understanding of the mechanisms of damage. Finally, the crack initiation and the first stage of crack propagation under high cycle fatigue conditions are investigated at a local scale on two different microstructures.

Orientador: Ruís Camargo Tokimatsu / Resumo: Esse trabalho tem a finalidade de projetar, com base em levantamento bibliográfico, uma prótese de disco intervertebral de Ti6Al4V pelo processo DMLS. Os sistemas de imagem de tomografias computadorizadas e ressonâncias magnéticas trabalham de maneira semelhante. Imagens em 3D de dados dos pacientes são construídas através da combinação de fatias 2D tomadas a partir de sistemas de sensores e da interpolação entre eles. A distância entre as fatias desses sistemas de imagens é grosseira comparada com a tecnologia da manufatura aditiva, portanto, esses processos combinam as imagens das fatias dentro de um software para criar um modelo 3D sobrepondo camadas, devido a essa sinergia entre os dois tipos de sistema, pesquisadores de todo o mundo tentam melhorar e inventar próteses para substituir o disco intervertebral através da ciência. Os resultados mostraram que a fabricação de uma prótese de disco com junta esférica pelo processo de manufatura aditiva é viável, porém nos segmentos menores, como na cervical ainda são difíceis de produzir devido à altura do disco intervertebral e ao limite da dimensão das camadas da manufatura aditiva, que atualmente estão por volta dos 20μm, por isso requerem tratamentos superficiais após sua fabricação. Espera-se que este trabalho possa ajudar futuros pesquisadores da área de biomecânica da coluna vertebral. / Abstract: This work has the purpose of designing, based on a bibliographical survey, an intervertebral disc prosthesis of Ti6Al4V by the DMLS process. Computed tomography (CT) imaging systems and MRIs work similarly. 3D images of patients data are constructed by combining 2D slices taken from sensor systems and interpolating between them. The distance between the slices of these imaging systems is rough compared to the additive manufacturing technology, so these processes combine the slice images within a software to create a 3D model overlapping layers because of this synergy between the two system types, researchers around the world try to improve and devise prostheses to replace the intervertebral disc through science. The results showed that the manufacture of a disc prosthesis with spherical joint by the additive manufacturing process is feasible, but in the smaller segments, such as in the cervical still difficult to produce due to the height of the intervertebral disc and to the limit of the size of the layers of the manufacture additives, which are currently around 20μm, so they require surface treatments after their manufacture. It is hoped that this work may help future researchers in the area of spinal biomechanics. / Mestre

Submitted by BRUNO FONTOURA DA SILVA COLMAN (brunocolman@hotmail.com) on 2018-05-03T15:19:22Z No. of bitstreams: 1 Dissertação de Mestrado - Bruno Colman Rev.36_03-05-2018.pdf: 5215084 bytes, checksum: 2152650458ee3ee274744cb5b222bb3c (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-05-03T17:05:09Z (GMT) No. of bitstreams: 1 colman_bfs_me_ilha.pdf: 5215084 bytes, checksum: 2152650458ee3ee274744cb5b222bb3c (MD5) / Made available in DSpace on 2018-05-03T17:05:09Z (GMT). No. of bitstreams: 1 colman_bfs_me_ilha.pdf: 5215084 bytes, checksum: 2152650458ee3ee274744cb5b222bb3c (MD5) Previous issue date: 2018-03-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esse trabalho tem a finalidade de projetar, com base em levantamento bibliográfico, uma prótese de disco intervertebral de Ti6Al4V pelo processo DMLS. Os sistemas de imagem de tomografias computadorizadas e ressonâncias magnéticas trabalham de maneira semelhante. Imagens em 3D de dados dos pacientes são construídas através da combinação de fatias 2D tomadas a partir de sistemas de sensores e da interpolação entre eles. A distância entre as fatias desses sistemas de imagens é grosseira comparada com a tecnologia da manufatura aditiva, portanto, esses processos combinam as imagens das fatias dentro de um software para criar um modelo 3D sobrepondo camadas, devido a essa sinergia entre os dois tipos de sistema, pesquisadores de todo o mundo tentam melhorar e inventar próteses para substituir o disco intervertebral através da ciência. Os resultados mostraram que a fabricação de uma prótese de disco com junta esférica pelo processo de manufatura aditiva é viável, porém nos segmentos menores, como na cervical ainda são difíceis de produzir devido à altura do disco intervertebral e ao limite da dimensão das camadas da manufatura aditiva, que atualmente estão por volta dos 20μm, por isso requerem tratamentos superficiais após sua fabricação. Espera-se que este trabalho possa ajudar futuros pesquisadores da área de biomecânica da coluna vertebral. / This work has the purpose of designing, based on a bibliographical survey, an intervertebral disc prosthesis of Ti6Al4V by the DMLS process. Computed tomography (CT) imaging systems and MRIs work similarly. 3D images of patients data are constructed by combining 2D slices taken from sensor systems and interpolating between them. The distance between the slices of these imaging systems is rough compared to the additive manufacturing technology, so these processes combine the slice images within a software to create a 3D model overlapping layers because of this synergy between the two system types, researchers around the world try to improve and devise prostheses to replace the intervertebral disc through science. The results showed that the manufacture of a disc prosthesis with spherical joint by the additive manufacturing process is feasible, but in the smaller segments, such as in the cervical still difficult to produce due to the height of the intervertebral disc and to the limit of the size of the layers of the manufacture additives, which are currently around 20μm, so they require surface treatments after their manufacture. It is hoped that this work may help future researchers in the area of spinal biomechanics. / CAPES - PROPG

Orientadores: Cecília Amélia de Carvalho Zavaglia, Carmo Roberto Pelliciari de Lima / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T04:15:56Z (GMT). No. of bitstreams: 1 Goncalves_FernandodeAlmeida_D.pdf: 4153645 bytes, checksum: fe7e541e43fe3f147ac65eff5bc547f0 (MD5) Previous issue date: 2012 / Resumo: A necessidade de melhorar as características superficiais da liga Ti-4Al-6V usada em implantes ortopédicos, levou à pesquisas no sentido de estudar a modificação da superfície dos implantes através da deposição de revestimentos cerâmicos resistentes à corrosão, ao desgaste e biocompatíveis, por vários métodos: eletroquímica, física a vapor, eletroforética, por sol-gel, biomimética e por aspersão térmica a plasma, entre outras. A aspersão térmica a plasma é o processo mais utilizado comercialmente, pois é rápido e reprodutível. As biocerâmicas mais utilizadas para revestimento, com sucesso, são as de fosfato de cálcio (hidroxiapatita-HA, betafosfato tricálcico [o -TCP] e uma mistura dessas duas fases). A adesão dessas biocerâmicas ao tecido ósseo possuí bom desempenho é bastante discutida na literatura. A comunidade médica tem algumas restrições ao uso desses implantes metálicos revestidos por cerâmicas, com relação à interface metal-cerâmica, cuja adesão é considerada baixa. Neste trabalho foi estudado a adesão metal/cerâmica em implantes revestidos por aspersão térmica à plasma (ATP) com cerâmica, mais especificamente liga de titânio (Ti-6Al-4V) revestida com titânia (TiO2) sem e com tratamento térmico a vácuo, com o intuito de verificar uma possível melhoria nessa adesão. A cerâmica utilizada neste trabalho foi a titânia, uma vez que é uma cerâmica biocompatível e osseointegrável, que é bastante utilizada para revestir implantes. Para a execução do trabalho foram confeccionados diversos corpos de prova, os quais foram revestidos por titânia por aspersão térmica à plasma, tratados termicamente e caracterizados segundo procedimentos contidos em normas e trabalhos científicos correlacionados que norteiam o assunto proposto. Foram utilizadas as seguintes técnicas de caracterização: análise granulométrica dos pós cerâmicos, difração de raios X, verificação da porosidade, microscopia óptica e eletrônica de varredura, verificação da rugosidade das amostras. Especial ênfase foi dada aos ensaios de adesão metal-cerâmica: ensaios de adesão por tração, flexão e riscamento. Tentou-se utilizar, sem sucesso, os ensaios de microdureza para avaliar a adesão. Como resultados, verificou-se uma boa qualidade nas amostras da liga Ti-4Al-6V revestidas por titânia por aspersão térmica a plasma. Através das três técnicas de avaliação da adesão, verificou-se uma ligeira melhoria dessas características pelo tratamento térmico a vácuo, no ensaio de riscamento a carga crítica aumentou de 53N para 62N, no ensaio de tração a tensão de fratura aumentou de 10,5MPa para 17,4MPa e no ensaio de flexão a tensão de fratura aumentou de 153,3MPa para 193,1MPa. Comparando com valores encontrados na literatura, a adesão Ti-4Al-6V/TiO2 ficou superior a Ti-4Al-6V/HA nas mesmas condições de deposição / Abstract: The need to improve the surface characteristics of the alloy Ti-4Al-6V used in orthopedic implants, increase researches with the focus into the surface modification, using deposition of ceramic coatings resistant to corrosion, wear and more biocompatible by various methods: electrochemistry, physical vapor, electrophoretic, by sol-gel, biomimetics and by thermal plasma, among others. The plasma spray technique is the process more used commercially because it is fast and reproducible. The bioceramics most used for coating, are calcium phosphate (hydroxyapatite-HA, beta-tricalcium phosphate, o -TCP and a mixture of these two phases). The adhesion of these bioceramics to the bone tissue is quite discussed in literature, presenting a good performance. However, the medical community has some restrictions on the use of metal implants with ceramic coating, since the metal-ceramic interface is considered low. In this work the aim is to study the adhesion metal/ceramic-coated implants in the thermal spray plasma (ATP), using titanium alloy (Ti-6Al-4V) coated with titania (TiO2) with and without vacuum heat treatment in order to check a possible improvement this adherence. The ceramic used in this work was the titania, since it is biocompatible and bioactive, and it is quite used to coat dental implants. For the execution of the work were made several specimens, which were coated with titania by plasma thermal spray, heat treated and characterized according to procedures and standards contained in scientific papers related to guide the proposed subject. The following characterization techniques it were used: particle size analysis of ceramic powders, X-ray diffraction, analysis of the porosity, optical microscopy and scanning electron microscopy, scanning the roughness of the samples. Special emphasis was given to tests of metal-ceramic adhesion: adhesion assays for tensile, bending and scratching. Micro hardness tests carried out, however the results were not significant. The summary of this project were that this alloy present a good quality coated by titania. The methods of increase the adhesion, showed a slight improvement of these characteristics by vacuum heat treatment, the result of the scratching test showed that the critical load increase to 62N instead 53N, when analyzed the results of tensile test it also had an increase 17,4MPa instead 10,5 MPa, the bending test presented higher results 193,1MPa in contrast to 153,3MPa for the samples without treatment. Compared with values found in the literature, the adherence of Ti-4Al-6V/TiO2 was greater than Ti-4Al-6V/HA / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Dans l’optique de maîtriser l’industrialisation des pièces complexes, les efforts de coupe sont une source riche d’informations. Bien que la prédiction des efforts de coupe soit un sujet largement traité par la communauté scientifique, quelques verrous subsistent. Les travaux de cette étude visent à enrichir les modèles existants sous deux principaux aspects : une étude approfondie de l’influence des conditions de contact en dépouille associées à la géométrie de pièce et l’effet de l’usure de l’outil sur l’évolution des efforts de coupe au cours du temps. Pour ce faire, plusieurs expérimentations instrumentées sont réalisées afin de déterminer les paramètres influents à introduire dans les modélisations. S’appuyant sur ces observations, des modélisations, selon une approche phénoménologique, sont développées pour estimer respectivement le niveau d’usure de l’outil, les efforts de coupe et leur évolution fonction au cours du temps. Ces développements sont conduits pour les techniques de fraisage, de tournage intérieur et de tournage extérieur appliquées à l’usinage de l’alliage de titane aéronautique Ti6Al4V. Les méthodologies présentées dans cette étude sont transposables vers d’autres nuances d’alliages de titane afin de couvrir un domaine d’application large en industrie. / In order to control complex parts industrialization, cutting forces can be relevant data. Although cutting force prediction is a well-known subject by the scientific community, it still exists some ways of improvement. This research work focuses on the cutting force modelling enhancement according to two main points. Firstly, an analysis of clearance face contact conditions, linked to part geometry, effect on cutting forces. Secondly, the effect of flank wear on cutting force evolution with respect to the time. Based on experiments, in order to highlight relevant parameters to introduce in the new model, cutting force and flank wear models are formulated according to mechanistic approach. These developments are applied in milling, turning (boring, cylindrical turning and face turning) onTi6Al4V titanium alloy. Methodologies presented in this study can be easily adapted to others titanium alloys shades in order to cover large industrial range of applications.

Abstract Whenever a foreign material is implanted into a human body an implant–tissue interface area forms between them. In this microenvironment, interactions take place between the implant and the surrounding tissue. The implantation of a biomaterial into tissue results in injury and initiation of the inflammatory response. This host response to biomaterials is an unavoidable series of events that occur when tissue homeostasis is disturbed by the implantation process. In bone tissue, biocompatible implants must initially be capable of strong bone implant contact and subsequently, allow the normal bone remodeling cycle around the implant. NiTi is a metal alloy composed of approximately a 50:50 ratio of nickel and titanium. It possesses shape memory and superelasticity properties, which make it an interesting biomaterial. NiTi has two phases: austenite and martensite. A decrease in temperature or applied stress induce the austenite-to-martensite transformation. Heating or removing the stress restores the parent austenite phase. The alloy in its martensite structure can be reshaped and strained several times more than a conventional metal alloy without irreversible deformation of the material. The alloy returns to its original shape as it changes from martensite-to-austenite. This transformation is seen as the macroscopic shape memory effect. This study further investigated the biocompatibility of NiTi, especially the bone cell response to both austenite and martensite. Different surface treatments were investigated in order to improve and possibly even control NiTi's bioactivity as a bone implant material. Osteoclasts grew and attached well on the austenite NiTi phase, but the results indicated that the biocompatibility of martensite NiTi was compromised. Oxidation of the NiTi surface improved osteoblast attachment and viability. This was due to the formation of a TiO2 surface layer of moderate thickness. Coating the NiTi surface with the extracellular matrix protein fibronectin was shown to enhance osteoblast proliferation and increase the number of cells in the G1 cell cycle stage. Austenite was more prone to show these effects than martensite. A sol-gel derived titania-silica surface treatment was observed to increase the bone implant contact of functional NiTi intramedullary nails. The surface treatment was most effective with the constant bending load provided by the NiTi nail.

The thesis is dedicated to welding combination of titanium alloy Ti-6Al-4V and austenitic steels 1.4301 by electron beam. Based on literature studies of bonding titanium and its alloys with steels, it was proposed to select for welding interlayer of copper, which could limit the impact of intermetallic phases on the mechanical properties of the weld seam and enable the creation of weld. For welding the pipe samples were used three methods of welding with various welding parameters. Samples which remain after thermal cycling vacuum-tight, were then further analyzed (micro-hardness, tensile test, etc.).

<p> High-end optical grade applications would benefit greatly from the unique mechanical and chemical properties of titanium alloys. However, the standard process of manufacturing optical components has not been explored in depth for titanium alloys. </p> <p> Thus the focus of this work was to extend ultra precision machining technology to produce optical grade surfaces on titanium components. An optical surface is characterized by surface roughness less than 10nm R_rms which are typically produced with single crystal diamond tools having a cutting edge radius on the order of 50-100 nm. A cutting speed of 60m/min, feed rate of 1.5 µm/ rev and depth of cut of 2 µm, was identified to achieve the surface finish target, but the practical limitation of this process was still with tool life and the rapid degradation of surface finish over time. </p> <p> This was attributed to the adhesion of titanium material on the tool that resulted in material pull out and side-flow during machining. Results obtained from the characterization of the tool and workpiece led to the identification of graphitization as the initial wear mechanism. As the cutting edge rounds-off due to graphitization, the rate of adhesion of the workpiece material onto the tool increased. For this reason solutions were explored that would reduce the graphitization process and delay the onset of intense adhension. </p> <p> Thus a coating technology involving Perfluoro Polyether (PFPE) was chosen. Tribometer analysis under a load of 500N and temperature of 450ºC between the uncoated and PFPE coated diamond tools and titanium pins showed a remarkable reduction in COF from 0.275 to 0.05. A significant enhancement in tool life and surface quality was also achieved in single point diamond turning (SPDT) of titanium alloys using PFPE coated diamond tools. Tool life was based on an assessment of the cutting length achieved before the surface roughness exceeded the targeted value of 10 nm R_rms and it improved from 1.25 km and 5.1 km with PFPE coated tools. </p> / Thesis / Doctor of Philosophy (PhD)

Titanium and its alloys are widely used in applications ranging from aeroengines and offshore equipment to biomedical implants and sporting goods, owing to their high ratio of strength to density, excellent corrosion resistance, and biomedical compatibility. Among the titanium alloys used in aerospace, Ti-6Al-4V (an α+β alloy) is the most widely used, in applications in which the temperature may reach 350°C, at which point it retains good fatigue and fracture properties as well as moderate tensile strength and ductility. These alloy properties are dependent on variables such as crystalline structure, alloy chemistry, manufacturing techniques and environmental conditions during service. These variables influence the microstructure and mechanical properties of titanium alloys. With regard to the alloy chemistry and operating environment, the focus of the present work is to understand the influence of boron and hydrogen on the microstructure and selected mechanical properties of cast Ti-6Al-4V. The addition of boron to cast Ti-6Al-4V (0.06 and 0.11 wt% in this work) refines the coarse “as cast” microstructure, which is evaluated quantitatively using FoveaPro image analysis software. Compression testing was performed using a Gleeble 1500 instrument, by applying a 10% strain at different strain rates (0.001, 0.1 and 1 s-1) for temperatures in the range 25-1100°C. The tests were performed to evaluate the effect of boron on the mechanical properties of the alloy. It was observed that there is an increase in the compressive strength, predominantly at room temperature, of cast Ti-6Al-4V after the addition of boron. Metallographic evaluation showed that this increase in strength is a likely result of reductions in both the prior β grain and α colony dimensions, which is caused by boron addition. Studies in a hydrogen environment at 150 bar showed that cast Ti-6Al-4V exhibited lower yield strength and lower ultimate tensile strength in comparison with those properties measured in an air environment. No significant change in the ductility was observed. It was also noted that in a high strain range (≈2%) the low cycle fatigue (LCF) life was significantly reduced in hydrogen compared with air. Microstructural and fractographic characterization techniques were used to establish the role of hydrogen on the deformation mechanism by analysing the crack propagation path through the microstructure. It is seen that cracks tend to propagate along the interface between prior β grain boundaries and/or along the α colony boundaries