O objetivo deste trabalho foi desenvolver uma forma alternativa de se produzir alvos para irradiação contendo urânio, destinados à produção do par de radionuclídeos 99Mo-99mTc. Estes alvos foram obtidos por metalurgia do pó, utilizando-se pós de níquel e de cobre, servindo o compactado como meio de encapsulamento para um cilindro de urânio a ser irradiado. O desenvolvimento compreendeu as etapas de caracterização química e física dos pós-utilizados. Os alvos foram compactados em prensa uniaxial e em prensa isostática a frio. As amostras foram sinterizadas em três atmosferas diferentes: argônio, hidrogênio e em alto vácuo. Quando do uso conjunto de cobre e níquel, foi feita sinterização por dois corpos, i.e., um compactado de níquel contendo o núcleo para ser irradiado e um compactado de cobre para servir de infiltrante. Isto, visando a eliminação de porosidade interconectada, permitindo o selamento do conteúdo físsil no interior do compactado. Os alvos após sinterização foram caracterizados fisicamente sendo avaliada a massa específica, pelo método geométrico e pelo princípio de Arquimedes. A porosidade foi medida pela técnica de porosimetria de mercúrio. Os alvos prontos foram caracterizados micro estruturalmente por microscopia óptica e eletrônica de varredura. Os resultados indicaram que a densificação do níquel foi diretamente proporcional à pressão de compactação obtendo-se 87% de densidade relativa após prensagem a 800 MPa (limite superior de compactação para ligas metálicas) e sinterização por 4 h a 600 ºC em atmosfera de hidrogênio. A sinterização por dois corpos (níquel com cobre) mostrou-se promissora para o uso como invólucro para núcleos, em termos de integridade estrutural e selamento devido à ausência de porosidade interconectada. / The objective of this work was to develop an alternative way to obtain targets for irradiation, containing uranium, destined for the production of the radionuclide pair 99Mo-99mTc. The targets were obtained using powder metallurgy using nickel and cooper powders, serving the compact as a medium for encapsulation of a uranium cylinder to be radiated. The development started with the chemical and physical characterization of the used powders. The targets were compacted either in uniaxial press and cold press isostatic. The samples were sintered at three different atmospheres: argon, hydrogen and high vacuum. In the case of use of nickel and copper, it was used the two bodies technique for sintering, i.e., a nickel compact containing a core to be irradiated and the cooper used as infiltrant. This was aiming at the elimination of interconnected porosity, allowing the sealing of any fissile content in the interior of the compact. The targets were physically characterized after sintering the density being evaluated by geometrical method and the Archimedes principle. The porosity was measured by the technique of mercury porosimetry. The targets were microstructurally characterized using optical and scanning electronic microscopy. The results indicated that the nickel densification was directly proportional to the compaction pressure yielding 87% relative density after pressing at 800 MPa (upper limit for alloys compaction) and sintering for 4 h at 600 °C in hydrogen atmosphere. Sintering of two bodies (nickel and copper) has shown some feasibility for use as core casing in terms of structural integrity and sealing due to the absence of interconnected porosity.

Orientador: João Batista Fogagnolo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T18:12:15Z (GMT). No. of bitstreams: 1 SallicaLeva_Edwin_M.pdf: 25527220 bytes, checksum: e74531ec342d519e6163a514595cb183 (MD5) Previous issue date: 2012 / Resumo: Peças fabricadas em titânio com estrutura porosa apresentam vantagens como material para implantes basicamente pela redução do módulo de elasticidade, o que aproxima sua rigidez à de tecidos ósseos, tornando-as mais adequadas á sua função. Neste trabalho apresenta-se um estudo da microestrutura e propriedades mecânicas de peças porosas de Ti-6Al-4V fabricadas por sinterização seletiva a laser, que é uma das técnicas de prototipagem rápida, que consolida, camada a camada, peças com geometria complexa a partir de pó. As estruturas porosas foram modeladas em programa CAD e fabricadas em um equipamento EOSINT M 270. Os modelos computacionais têm forma cúbica com 15 mm de aresta e possuem arquitetura interna de poros interconectados também de forma cúbica. A porcentagem de porosidade foi variada na faixa de 61 a 76%, mudando-se o número e o tamanho dos poros e a espessura das paredes internas. Pó atomizado da liga Ti-6Al-4V foi utilizado como matéria-prima. Utilizaram-se dois níveis de energia fornecida, variando-se alguns parâmetros do processo, como a velocidade de varredura do feixe de laser, a potência do laser e distância entre linhas de sinterização. As amostras sinterizadas foram caracterizadas por microscopia óptica e eletrônica de varredura, ensaios de dureza e compressão. Em uma segunda etapa, foram realizados tratamentos térmicos em amostras com 69% de porosidade projetada. As peças sinterizadas apresentaram microestrutura martensítica, porosidade interconectada na faixa de 63 a 77%, com boa formação de parede, e superfície rugosa com aderência de partículas de pó não sinterizado. Testes de compressão das amostras sinterizadas mostraram que o módulo de Young variou de 5,36±0,01 a 8,73±0,07 GPa, o limite de escoamento variou de 91,5±0,7 a 170±5 MPa e a resistência mecânica à compressão variou de 106±1 a 219±5 MPa, dependendo da porcentagem de porosidade. O aumento da energia do processo resultou em paredes mais finas, para o mesmo modelo, e também uma porosidade não controlada, interna às paredes das peças, o que reduziu a rigidez e a resistência mecânica das peças. Os tratamentos térmicos feitos nas peças porosas com 69 % de porosidade projetada promoveram mudanças microestruturais, mas não resultaram em aumento das propriedades mecânicas / Abstract: Titanium porous parts have advantages as materials for implants due to their lower modulus of elasticity, which approximates their stiffness to the bone tissue stiffness, making them more appropriate to their biofunction. In this work we present a microstructural characterization and a mechanical property evaluation of porous parts of Ti-6Al-4V produced by selective laser sintering, which is a rapid prototyping technique that consolidates, layer by layer, parts with complex geometry from powder. The porous structures were designed in a CAD program and manufactured in the EOSINT 270 laser-sintering system. The computational models have cubic shape with 15 mm edge and an internal architecture of interconnected pores also with cubic shape. The percentage of porosity was varied in the range from 61 to 76 % by changing the number and size of the porous and the thickness the struts. Powder prealloyed of Ti-6Al-4V was using as raw material. Two energy levels were tested, by varying the process parameters, such as laser power, speed of laser and spacing between laser tracks. The as-sintered samples were characterized by optical and scanning electron microscopy, hardness and compressive tests. Further, thermal treatments were performed on samples with 69% of modeled porosity. The sintered parts presented martensitic microstructure, with interconnected porosities varying from 63-77%, with good formation of struts, and rough surface with adhesion of no-sintered powder particles. The compression tests of as- sintered samples showed the Young's modulus values ranging from 5.36 ± 0.01-8.73 ± 0.07 GPa, the yield strength values ranging from 91.5 ± 0,7-170 ± 5 MPa and the compressive strength values ranging from 106 ± 1-219 ± 5 MPa, depending on the percentage of porosity. Increasing the energy of the process resulted in thinner struts for the same model and also a no-controlled porosity in the internal struts of parts, which reduced the stiffness and the mechanical strength of the parts. Heat treatments performed in the porous parts with 69% porosity promoted microstructurals changes, but did not result in an increase of the mechanical properties / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

La technologie Spark Plasma Sintering (SPS) permet la conception de matériaux denses avec des microstructures fines. Il s’agit d’une variante du pressage à chaud (HP) qui utilise un courant pulsé pour chauffer la matrice et le matériau. Les phénomènes mis en jeu restent mal compris et sujets à controverse, laissant plusieurs interrogations : - Pourquoi le frittage par SPS apparaît-il plus efficace que les méthodes de frittage sous charge classiques ? Quels sont les mécanismes de densification et de consolidation activés qui déterminent l’élaboration par SPS ? Le passage du courant joue-t-il un rôle dans ces mécanismes et si oui lequel ? Ce travail vise à répondre à ces questions dans le cas de poudres de cuivre sphériques de 10 à 50 µm. Des comparaisons systématiques ont été réalisées avec le pressage à chaud classique, dans des conditions identiques. La cinétique de densification a été étudiée à l’échelle macroscopique et à l’échelle de la microstructure. L’observation de la formation des cous de frittage a été réalisée à partir de fractographies et de sections polies. La densification est assurée par la déformation des particules due à la charge appliquée et à l’augmentation de la température. Aucune différence, ni macroscopique, ni microscopique, n’a été mise en évidence entre l’élaboration par HP et celle par SPS, même lorsque des conditions favorables à la mise en évidence ont été utilisées : couches d’oxyde développée sur les particules, passage du courant forcé dans l’échantillon, fortes intensités appliquées par des « pulses » de courant. Dans les conditions étudiées, il n’apparaît aucun effet spécifique lié au courant. / Spark plasma sintering is a manufacturing process that leads to dense materials with fine microstructures. SPS combines heating and uniaxial load as well as the Hot Pressing (HP) process but the material is heated using a pulsed current. The phenomena occurring during SPS are not fully understood and are still an open point: -Which densification and consolidation mechanisms are involved during SPS? -Why is sintering by SPS more efficient than sintering by traditional ways such as HP? –Does electrical current modify the sintering mechanisms? The aim of this work is to answer these questions in the case of spherical copper powder (from 10 to 50 µm). Comparisons between SPS and HP were performed using the same process conditions. The densification rate was studied macroscopically and microscopically. The evolution of the necks between particles was followed by cross sections and fractography. The densification is realized by plastic deformation due to the applied load and the temperature increase. No difference between SPS and HP was observed although sintering conditions favorable to the occurrence of specific phenomena were applied: oxide layer coating the particles, current forced through the sample, high intensity using a pulsed current. In the studied conditions, no specific effect was observed due to the current presence.

L’élaboration de multimatériaux en couches par métallurgie des poudres permet de réduire les coûts de fabrication, et d’augmenter les performances d’une pièce. Néanmoins, l’assemblage de multicouches engendre bien souvent des fissures ou même des délaminations, qui nuisent aux bonnes propriétés de la pièce. Ces travaux de thèse ont donc pour objectif de mieux comprendre quels peuvent être les paramètres importants à prendre en considération et leurs influences pour l’élaboration de multimatériaux. Pour cela, le cofrittage de trois couples de bimatériaux en couches massives a été étudié. Pour apprécier la cause de l’endommagement dans les bicouches, un dispositif de suivi in situ sans contact a été développé afin d’observer les déformations, les fissures, et les délaminations. De plus, la simulation du cofrittage grâce à un modèle de loi de comportement de type Binghamien a été réalisée dans le but de connaître le champ de contraintes résiduelles : les fissures observées ont été corrélées à ce champ de contraintes. Pour un premier couple de matériaux sans aucune interaction (Al2O3/ZrO2), il apparait nécessaire d’avoir des retraits qui débutent à des températures similaires, des retraits finaux proches, et une densification incomplète pour éviter l’endommagement. L’étude concernant la présence d’une phase liquide à l’interface (Al2O3/WC-Co) a souligné que celle-ci accroit l’accroche à l’interface pendant le frittage, mais qu’elle la fragilise lors du refroidissement. En présence d’une réaction à l’interface (ZrO2/Ti) une forte accroche chimique permet même de contrecarrer les effets néfastes d’un fort différentiel de retrait final. / The multilayer materials processed by powder metallurgy allow reducing the manufacturing cost. However, the multilayers assembly often leads to cracks or even debonding, which decreases the piece properties. The main purpose of this work is to better understand which important parameters have to be taken into account and their influences on the multimaterials processing. In order to fulfil this objective, the cosintering of three different couples of bimaterials in thick layer has been studied. To identify the damaging reasons in the bilayers, an in situ monitoring device has been developed to observe deformations, cracks and debonding. Moreover, the cosintering simulation with a Binghamien law model was performed to evaluate the internal stresses field : the experimentally observed cracks were correlated with this internal stresses field. For a first couple of materials with no interaction (Al2O3/ZrO2), it appears the necessity to have shrinkages which begin at similar temperatures, similar final shrinkages and an incomplete densification to avoid damaging. The study concerning the presence of a liquid phase at the interface (Al2O3/WC-Co) underlined that this liquid phase increases the bonding during the sintering, but decreases it during the cooling. With a reaction at the interface (ZrO2/Ti), a strong chemical bonding allows to avoid the bad effects of an important differential final shrinkage.

Este trabalho tem como objetivo o projeto, construção e análise do funcionamento de uma máquina elétrica síncrona trifásica com núcleo do rotor produzido a partir da metalurgia do pó e ímãs de neodímio-ferro-boro para aplicação em aerogeradores. Tomando como base a máquina elétrica modelo VTOP da fabricante Grupo Voges, foram realizadas mudanças na forma construtiva dos núcleos do estator e do rotor. O pacote chapas que compõem o núcleo do estator foi montado de maneira que as ranhuras apresentem um ângulo de inclinação de 10º ao longo de toda a extensão da máquina. Para o rotor, foi projetado e construído um núcleo através do processo de metalurgia do pó utilizando como matéria-prima pó de ferro puro. A esse novo núcleo foram acrescentados ímãs de neodímio-ferro-boro. Após a montagem dos componentes, a máquina elétrica foi ensaiada em uma bancada de testes. Paralelamente com a confecção do núcleo foi efetuada a simulação computacional da máquina com três tipos diferentes materiais no núcleo do rotor. Os resultados encontrados indicaram que a metalurgia do pó é uma alternativa viável para produção do núcleo de máquinas elétricas. Entretanto alterações na topologia e na forma de fixação dos ímãs são necessárias para um melhor desempenho. / This work aims at the design, construction and performance analysis of a three-phase synchronous electric machine with a rotor core produced by powder metallurgy and neodymium-iron-boron magnets for application in wind turbines. Based on the electric machine VTOP model of the manufacturer Grupo Voges, changes were carried out in the constructive form of the stator and rotor cores. The bundle of plates that make the role of stator core were mounted with a 10º slope along the entire length of the machine. For the rotor, a core was designed and built by employing powder metallurgy process using pure iron powder as raw material. The neodymium-iron-boron magnets were added to this new core. After assembling the components, the electric machine was tested on a test bench. Simultaneously with the core fabrication, the machine was simulated with three different materials in the rotor core. The results indicated that powder metallurgy is a viable alternative to produce the core of electric machines. However, changes in the topology and shape of the magnets are necessary for better assembly, improving the performance.

The widespread use of titanium and its alloys in structural applications has been limited to few highend applications. The dominant reason for this being cost implications. These high costs arise from extracting titanium from its mineral form as well as that of the manufacturing processes to develop a final product. Since producing titanium products includes expensive starting stock, high machinability costs and high wastage, a need for a process that may minimize one or more of these factors is necessary. One such technology that exists is a branch of powder metallurgy (PM), direct powder rolling (DPR) which allows for a continuous approach to produce strip or sheet metal. Products developed by this process are however known to possess inferior properties to its wrought counterpart. The present study comprises of a parametric study observing how two different blends of powder differ in the development of Ti-6Al-4V strip by employing the blended elemental (BE) approach to direct powder rolling. The objectives of this work include predicting the compaction behavior of the two respective blends during powder rolling to inform the production of high density green strip and to compare the outcomes of the prediction method to experimentally determined results using a gravity-fed laboratory-scale rolling mill with roll diameter of 265 mm and roll width of 150 mm. Johanson’s rolling theory was applied to predict rolling outcomes and a fixed set of rolling parameters were implemented for the simulation and experimental segment of this dissertation. The two blends being investigated include blending titanium powder with an elemental blend consisting of aluminium and vanadium powders (B1) and a master alloy blend of a 60Al-40V master alloy (B2). These two blends were used to validate the Johanson simulated rolling data. Fixed parameters applied to the rolling mill included using a roll speed of 14 rpm, roll face width of 65 mm and gravity-fed hopper outlet diameter of 25 mm. Variable roll gaps of 0.5, 1 and 1.5 mm were studied. Average relative green densities of B1 and B2 strips achieved at a roll gap of 1 mm were 77% and 73% respectively. Rolling performance of the B1 powder blend were higher than that of B2, reaching higher green densities and showing superior formability, as rolling at smaller roll gaps was achievable for B1 and not B2. Green strength of B1 and B2 strips at a roll gap of 1 mm reflected similar outcomes where B1 strips required a greater breaking load to fracture samples when compared to B2 indicating a stronger self-supporting compact. Furthermore, the Johanson rolling model proved to overestimate reasonable roll pressure values, although, the general trend of compactibility between B1 and B2 powder blends was reasonably predicted showing B1 to be more compressible than B2 during powder rolling. iv Subsequent sintering at 1200 °C for 3 hours in a vacuum environment was applied to green strips to further densify and homogenize strips. Average relative sintered densities achieved for B1 and B2 strips rolled at a roll gap of 1 mm were 78% and 87% respectively. While green densities of B1 strips were higher than that of B2 strips, it was evident that the addition of the 60Al-40V master alloy to blend B2 resulted in superior sinterability as final sintered densities surpassed that of B1, even when starting at a lower green density after rolling. SEM/EDX was used to evaluate what effect sintering had on homogenization. A standard wrought Ti-6Al-4V specimen was used as the benchmark to compare homogenization results. B2 strips homogenized more than B1 strips when comparing to the baseline wrought sample. It was concluded that both B1 and B2 powders used to create Ti-6Al-4V strip by direct powder rolling (DPR) exhibited high levels of porosity and a subsequent step is necessary to fully densify the material. While B1 strips exhibit superior rollability with higher green densities and green strength; after applying a sintering practice to both B1 and B2 strips, B2 sintered densities surpassed those of B1 and prove to homogenize to a greater degree than B1 strips. The superior roll compaction ability and inferior sinterability for B1 powders was attributed to the elemental powder, aluminium. While the addition of ductile aluminium to B1 aids roll compaction, its low melting point results in large pores evolving at sintering temperatures almost twice its melting point.

The diploma thesis deals with evaluation of electrochemical corrosion characteristics of Mg-Zn systems prepared by powder metallurgy in SBF solution. The main aim of the thesis is to analyze the influence of chemical composition, achieved structure and parameters of the process of production of Mg-Zn systems on their electrochemical corrosion characteristics. The basic electrochemical properties of the prepared materials will be evaluated by electrochemical impedance spectroscopy. In order to clarify the mechanism of corrosion of materials, the immersion tests will be used, accompanied by metallographic observations.

During exothermic reactions a significant amount of heat is released. This heat can be further utilized for heating up chemical substances, chemical reaction initiation or welding. The first part of this thesis contains survey of thermodynamics and thermodynamics and thermochemistry of exothermic reactions, overview of commonly used exothermic processes as thermites and NanoFoil, summary of intermetallic systems and possibilites of powder metallurgy as a fabrication process of exothermic powder blends. Based on the survey part is designed experimental powder blend obtained by powder metallurgy. 18 powder samples were analysed; chemical composition was obtained by XRD and EDS analysis, on scaning electron microscope the morphology of powder particles was evaluated and by differential scanning calorimetry (DSC) the temperature of exothermic intermetallic reaction was determined. Furthermore a bulk intermetallic sample was sintered by spark plasma sintering process (SPS).

The diploma thesis deals with the preparation of the composite material based on the NiSi system using powder metallurgy supplemented by the sintering with the usage of SPS method (spark plasma sintering). Theoretical part contains general information about the mechanical-chemical process and sintering, while materials and methods used for experimental observation are explained in a separate chapter. Experimental part explains the procedure of the experiment and selected parameters of individual processes. In the experiment, two powder mixtures were created in order to form the NiSi phase in the maximum possible amount of powder material. After successfully reaching presence of the NiSi phase in the range of 87 to 89 wt. %, both mixtures were used to produce sintered samples at temperatures from 700 to 900 °C. Experiments showed the best results for sample number 2, which was sintered at 900 °C for 4 minutes. Resulting porosity was 0.9 % and hardness reached a maximum value of 718 HV 1. However, all sintered samples show cracks at room temperature associated with increased brittleness of the material.

A crankshaft is a component which is used to convert a reciprocating movement into rotating or vice versa. Through the past years classical manufacturing techniques did not leave space for a new approach regarding manufacturing this component. Powder Metallurgy provides a manufacturing technique which can revolutionize this procedure and make it more economical and more efficient. In order for this to be achieved, the crankshaft must be produced in different pieces. Webs, counter-webs and journal shafts must be produced individually and assembled together. The main challenge in this thesis is to understand if the crankshaft’s counter webs could be manufactured all in the same pieces or in as less pieces as possible. This thesis deals mostly with the technical requirements and proposing a new modular design. A kinematic-kinetic analysis is performed by using the values from the existing crankshaft which has been scanned and converted into a CAD model. The numerical values from the kinetic-kinematic analysis in Matlab are compared with a MBS model from Adams. Then the balancing of the crankshaft is analyzed and it is investigated how the counterweights should be arranged in space and what should be the mass and the geometrical properties of them. From the component’s design specifications, several models are generated and evaluated with the Pugh matrix. The original and the new proposed models are compared as far as concern the mass, center of mass, mass moment of inertia and natural frequencies. / En vevaxel är en motorkomponent som används för att omvandla den fram- och återgående rörelsen hos kolv och vevstake till en roterande rörelse. De klassiska metoderna att tillverka vevaxlar har varit dominerande och inte gett någon plats för alternativa tillverkningsmetoder. Powder manufacturing är en metod som kan revolutionera produktionens effektivitet och ekonomi. För att denna tillverkningsmetod ska vara möjlig måste vevaxeln tillverkas i delar. Webs, counter-weights och journal shafts måste produceras individuellt för att sedan sammanfogas. Den största utmaningen för denna avhandling är att förstå om vevaxelns counter webs kan tillverkas med samma form eller med så få olika former som möjligt. Denna avhandling handlar främst om att fastställa dessa tekniska krav och föreslå en ny, modulär design för PM. En kinematisk-kinetisk analys utförs med hjälp av en befintlig vevaxel som skannats och omvandlats till en CAD-modell. De numeriska värdena jämförs med en MBS-modell från Adams. Vevaxeln analyseras med avseende på balansering då motvikternas placering, massa och geometriska egenskaper undersöks. Nya modeller som följer de tekniska krav som krävs skapas och utvärderas med Pugh-matris. De nya föreslagna modellerna jämförs med den ursprungliga utformningen med tanke på massa, masscentrum, MMOI och egenfrekvenser.