Inconel 718 (IN 718) is widely used in applications, such as aircraft and power turbine components. Recently, fiber laser welding has become an attractive joining technique in industry for fabrication and repair of service-damaged components. However, a major limitation in the laser welding of IN 718 is that liquation cracking occurs. In the present work, autogenous fiber laser welding of IN 718 was used to study the effects of welding parameters and different pre-weld heat treatments on liquation cracking. Contrary to previous studies, a dual effect of heat input on cracking is observed. A rarely reported effect of heat input is attributed to process instability. Liquation cracking increases with pre-weld heat treatment temperatures that increase grain size and/or, possibly, intregranular boron segregation. The study shows that pre-weld heat treatment at 950oC can be used for repair welding of IN 718 without significant loss in cracking resistance.

Inconel 718 (IN 718) is widely used in applications, such as aircraft and power turbine components. Recently, fiber laser welding has become an attractive joining technique in industry for fabrication and repair of service-damaged components. However, a major limitation in the laser welding of IN 718 is that liquation cracking occurs. In the present work, autogenous fiber laser welding of IN 718 was used to study the effects of welding parameters and different pre-weld heat treatments on liquation cracking. Contrary to previous studies, a dual effect of heat input on cracking is observed. A rarely reported effect of heat input is attributed to process instability. Liquation cracking increases with pre-weld heat treatment temperatures that increase grain size and/or, possibly, intregranular boron segregation. The study shows that pre-weld heat treatment at 950oC can be used for repair welding of IN 718 without significant loss in cracking resistance.

The effect of retrogression and reaging heat treatment on corrosion fatigue crack growth behavior on AA7050 T73651 aluminum alloy is investigated. CT (Compact Tension) specimens are prepared in LS direction for fatigue crack growth tests . Samples are solution heat treated at 477 &deg / C and aged at 120 &deg / C for 24 h (T6 condition). After that, samples are retrogressed at 200 &deg / C for times of 1, 5, 30, 55 and 80 minutes in a circulating oil bath. Then, samples are re-aged at 120 &deg / C for 24 h (T6 condition). Hardness measurements are taken at different retrogression times and at the end of the heat treatment. Fatigue crack growth tests are performed at as received condition and at different retrogression times with sinusoidal loading of R=0.1 and f=1 in both laboratory air and corrosive environment of 3.5% NaCl solution. The highest fatigue crack growth resistance is observed for 30 min. and 5 min. retrogression for laboratory air and corrosive environment respectively. It is concluded that RRA can successfully be used to improve fatigue performance of this alloy.

Stable fixation of implants such as artificial teeth depends on the direct apposition of bone to the implanted material. While endosseous implants were traditionally allowed to "osseointegrate" over several months without carrying load, clinical and experimental data show that prostheses with roughened surfaces allow successful integration when subject to earlier loading and more challenging implant sites. However, to design implant surfaces for an optimal biological response requires an understanding of the mechanism by which roughened surfaces promote osseointegration. Research into this mechanism has, to date, focussed primarily on the response of osteoblastic cells to surface topography in vitro. While these have demonstrated some consistent trends in cell behaviour, the fundamental means by which cells sense and respond to roughness remain unclear. It has been suggested that cell responses to changes in topography may relate to differences in the proteins adsorbed from serum (in vitro). While experimental evidence indirectly suggests that physical features can affect protein adsorption, few studies have examined this with respect to surface roughness, particularly as a mediator of cell responses. To address this issue, cell culture and protein adsorption experiments were conducted on a limited range of surface textures. Titanium samples were ground to produce morphologically similar surfaces with three grades of roughness. A duplicate set of specimens were heated at 600°C for one hour, with the aim of masking potential variations in physicochemical properties with differing degrees of grinding. Osteoblast attachment and proliferation studies were conducted over a short time-frame of 48 hours or less, to highlight the effects of proteins adsorbed from serum rather than secreted by adherent cells. Gel electrophoresis provided a profile of the proteins adsorbed to each surface after 15 minutes, corresponding to the time by which the cells had settled onto the surface. Finally, confocal microscopy was used to examine cell morphology on each surface, and to visualize specific interactions between cellular structures and adsorbed adhesion-mediating proteins. Although the effects were inconsistent, attachment assays showed some indications that fewer cells attached in the first 90 minutes as roughness increased. This inverse cell number-roughness trend was significant at 48 hours; however, the variability in attachment assays prevented reliable separation of attachment and proliferation rate effects. While the reduction in cell number with increasing roughness is consistent with previous reports, it is typically observed at later time points, and thus may be increasingly confounded by contact inhibition and differentiation. Thermal oxidation of the titanium did not impact on osteoblast responses to roughness, although it significantly slowed cell proliferation. The latter result was unexpected on the basis of previous reports. One-dimensional gel electrophoresis revealed no significant differences in the composition of adsorbed layers with variations in roughness. However, as expected on account of wettability changes, the heat-treatment did correspond to significant changes in the adsorption profile. While this was not a highly sensitive analysis, it suggests that the cell responses to roughness changes were not governed by broadscale differences in the proteins initially available to adhering cells. In addition to the composition of the adsorbed layer, the distribution of proteins may also vary with topography. The immunofluorescence methods were not sufficiently sensitive to reveal the distribution of adsorbed adhesion proteins (vitronectin and fibronectin). However, the lack of clear labelling does suggest an absence of large accumulations due to specific topographic features. Further work is required to address this issue conclusively. Observations of cell morphology were consistent with widely-reported contact guidance phenomena on grooved surfaces, with elongation and alignment (with topography) increasing with groove depth. Cell elongation was also enhanced on the more hydrophilic, heat-treated titanium, but this effect diminished over time. Although increased elongation at 90 minutes corresponded to lower cell numbers at 48 hours, no causal relationship has yet been established.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

CNPq / Os aços inoxidáveis são amplamente utilizados nas indústrias químicas, petroquímicas, nucleares, de geração de energia, biomédica e de processamento de alimentos. Em geral os aços inoxidáveis apresentam boa resistência à corrosão, entretanto a aplicabilidade destes aços pode ser restringida pela dureza ou pela resistência a corrosão. Usualmente os aços de alta resistência e dureza apresentam elevados teores de carbono, apresentando uma estrutura martensítica, com consequente redução da resistência à corrosão. Por outro lado os aços com maior resistência a corrosão apresentam menor dureza e consequente menor resistência ao desgaste. Diversas soluções têm sido implementadas no sentido de melhorar a resistência a corrosão e ao desgaste simultaneamente desses materiais. Dentre estas a adição de nitrogênio na superfície através da nitretação a plasma, implantação iônica, tratamento térmico de solubilização após nitretação a plasma (SHTPN – Solution Heat Treatment after Plasma Nitriding). Este trabalho tem como objetivo determinar os parâmetros de SHTPN que possibilite obter martensita de nitrogênio na superfície do aço AISI 409, bem como, a avaliação de sua resistência à corrosão. Foi possível verificar uma melhora na resistência à corrosão das condições tratadas por SHTPN, assim como um aumento na resistência mecânica, avaliado pelo perfil de dureza da camada superficial tratada. / Stainless steels are widely used on chemical, petrochemical, nuclear, energy generation, biomedical and food processing industries. In general, stainless steels present good corrosion resistance. However, the application of these materials can be restrained by the hardness and the corrosion resistance. Usually, high strength steels present high carbon content and martensitic structure, what can consequently cause a reduction on corrosion resistance. On the other hand, high corrosion resistance steels present low hardness and weak wear properties. Thereby, many solutions have been made to improve simultaneously wear properties and corrosion resistance of these materials, specially related to the introduction of nitrogen on the surface, through plasma nitriding, ion implantation and SHTPN (Solution Heat Treatment after Plasma Nitriding) processes. The aim of this paper is to determine SHTPN parameters that can form nitrogen martensite on the surface of AISI 409 stailess steel, as well as the evaluation of its corrosion resistance. It was verified an improve on corrosion resistance conditions of SHTPN treated samples. Aditionally, there was an improve on mechanical resistance showed by hardness profiles.

De nombreux gestes médicaux utilisent des aiguilles. Il est proposé une solution de principe pour contrôler la trajectoire d’une aiguille lors son insertion. Ce contrôle de trajectoire permet d’éviter des obstacles et atteindre une cible avec plus de précision. La solution de principe proposée repose sur l’utilisation des alliages à mémoires de forme de type Nickel-Titane (NiTi) et des traitements thermiques localisés. Une méthode expérimentale originale pour caractériser les alliages NiTi est développée. Cette méthode repose sur l’utilisation d’un dispositif expérimental permettant de faire des mesures et analyses mécaniques dynamiques (DMA) lors d’un essai de traction ou au cours d’un balayage en température sous contrainte. Ces mesures DMA ont permis de détecter les nombreux phénomènes présents dans ces alliages : élasticité, transformation de phase, réorientation,localisation, plasticité. Les résultats des mesures effectuées sur un fil commercial de NiTi sont présentés et analysés. L’analyse de l’évolution du module de conservation a permis de mettre en évidence les différentes séquences de transformation et de définir les domaines d’existence des phases en fonction de la contrainte et de la température. Des valeurs de modules d’élasticité de l’austénite, de la martensite et de la phase R sont proposées. Enfin,des modèles d’évolution du module de conservation lors d’un essai de traction et d’un balayage en température sous contrainte sont proposés. Une dernière partie concerne l’étude des effets des traitements thermiques sur un fil NiTi étiré à froid. Une gamme de traitements thermiques a été réalisée sur un fil NiTi. Les propriétés thermomécaniques ont été investiguées à la fois par des essais de traction isothermes et des mesures DMA en balayage en température sous contrainte. / Many medical procedures use needles. A solution is proposed to control and modifyneedle trajectory during its insertion. This steerable needle must be able to avoid anobstacle and reach the target with more accuracy. The solution uses Nickel Titanium(NiTi) shape memory alloy. A new experimental method is proposed to characterize NiTiwires. This method is based on experimental device wich allows to perform DynamicMechanical Analysis (DMA) during a tensile test or during a temperature sweep understress. DMA measurements can detect many phenomena : elasticity, phase transformation,reorientation, plasticity. Results for a commercial NiTi wire are presented and analyzed.Storage modulus evolution analysis shows multistage phase transformations for which thestress-temperature diagram has been established. Values of elastic modulus are determinedfor austenite, martensite and R phase. Estimation models are proposed to determinestorage modulus evolution during tensile test with DMA and temperature sweep understress with DMA. The last part of this work studies the effect of heat treatment on acold worked Niti wire. A range of heat treatments was performed. Thermomechanicaltreatment effects were investigated both with tensile tests and temperature sweeps understress with DMA.

The vehicles industry is facing increasing demands for fuel efficiency and cost reduction due to environmental legislation, sustainability and customer demands. Therefore, there is a great need to develop and produce lightweight components by using materials and processes that offer higher specific strength and/or design optimization. Semi‐solid aluminium casting offers design freedom and castings with lower shrinkage and gas entrapment defects compared to high pressure die castings. The lack of understanding of microstructure and defect formation, and design data, for semi‐solid castings is a barrier for foundries and designers in the vehicles industry to use semi‐solid castings. In this study, the effect of two grain refiners on slurry formation and surface segregation of semi‐solid Al‐7Si‐0.3Mg castings produced by the Rheometal™ process was evaluated. The influence of grain refinement on primary α‐Al grain size, shape factor and solid fraction was analysed in addition to the solute content of the surface segregation layer. The influence of magnesium on the formation of intermetallic phases during solidification and the heat treatment response of Al‐7Si‐Mg semi‐solid castings was investigated. The magnesium content was varied from 0.3 to 0.6wt.% and the semi-solid castings were analysed in the T5 and T6 conditions. Energy dispersive spectroscopy was used to identify the intermetallic phases formed during solidification. Tensile testing was performed and the results were correlated to the magnesium and silicon concentration measured in the interior of the α‐Al globules formed during slurry preparation. The results suggest that the addition of grain refiner decreases the solid fraction obtained in the Rheometal™ process. However, no significant effect was observed on the α‐Al grain size and shape factor. A good correlation was obtained between the magnesium concentration in the interior of the α‐Al globules formed during slurry preparation and the offset yield strength for all alloys. The low magnesium solubility in α‐Al at temperatures in the solidification range of the Al‐7Si‐Mg alloys is suggested to be the reason for the low hardening response for the T5 heat treatment compared to the T6 condition.

OLIVEIRA, Ticiane Coelho Abreu de. Estudo da qualdiade microbiológica, química, físico-química e sensorial de cenoura (Daucus carot, L.) submetida à tecnologia Sous vide produzida em escala industrial. 2012. 98 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos, Fortaleza-CE, 2012 / Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-28T16:00:36Z No. of bitstreams: 1 2012_dis_tcaoliveira.pdf: 741298 bytes, checksum: 355c053111b742e1184f6a1d19ca4110 (MD5) / Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-28T16:00:50Z (GMT) No. of bitstreams: 1 2012_dis_tcaoliveira.pdf: 741298 bytes, checksum: 355c053111b742e1184f6a1d19ca4110 (MD5) / Made available in DSpace on 2016-06-28T16:00:50Z (GMT). No. of bitstreams: 1 2012_dis_tcaoliveira.pdf: 741298 bytes, checksum: 355c053111b742e1184f6a1d19ca4110 (MD5) Previous issue date: 2012 / The carrot is a crop rich in carotenoids, pro-vitamin A, minerals and carbohydrates, and is a food with high nutritional value. Brazil is among the five largest producers and consumers of carrot (Daucus carot L .) in the world, concentrating its production in the Southeast. In search of products more attractive, practical, nutritious and healt hy, the consumer's sous vide technology is an alternative technology for the industry in providing food ready for consumption. The sous vide consists in cooking food packaged in plastic vacuum -sealed, subjected to temperatures lower than 100°C for extended periods of time, chilled quickly and stored under refrigeration. The aim of this study was to evaluate the quality and shelf life of carrots ( Daucus carot L.) diced submitted to sous vide technology, produced on an industrial scale. The samples were subje cted to physical and chemical analysis and chemical, microbiological and with three replications, with five repetitions of the products, and soon after processing by 2, 4, 6 and 8 weeks of storage (3°C). Sensory analysis was carried out on days 0 and 4 weeks, with a repeat. The results indicated a significant difference of 5% (p ≤0.05) in carbohydrate, protein, ash, titratable acidity and chromaticity between the carrot fresh carrot and processed by sous vide technology at time 0. In times of 2, 4, 6 and 8 weeks of storage at 3°C difference was significant (p ≤ 0.05) only for protein and total acidity. In sensory analysis, no significant difference (p ≤ 0.05) in any of the attributes studied. It was also observed that the technology sous vide was effective in eliminating vegetative cells of micro-organisms pathogenic and spoilage, yet not been able to eliminate spores. The carrot processed by sous vide technology retains its nutritional characteristics, sensory, chemical and microbiologically stable for up to eight weeks of storage at 3ºC. / A cenoura é uma olerícola rica em carotenóides, pró-vitamina A, minerais e carboidratos, constituindo um alimento com alto valor nutritivo. O Brasil está entre os cinco maiores produtores e consumidores de cenoura (Daucus carot L.) do mundo, concentrando sua produção na região sudeste. Na busca de produtos mais atrativos, práticos, nutritivos e saudáveis pelo consumidor, a tecnologia sous vide surge como uma alternativa tecnológica para a indústria no fornecimento de pratos prontos para consumo. O sous vide consiste em cozinhar alimentos acondicionados em embalagens plásticas seladas à vácuo, submetidos a temperaturas inferiores à 100°C por longos períodos de tempo, resfriados rapidamente e armazenados sob refrigeração. O objetivo desse trabalho foi avaliar a qualidade e a vida de prateleira de cenouras (Daucus carot L.) cortadas em cubos submetida a tecnologia sous vide, produzida em escala industrial. As amostras foram submetidas as análises físico-químicas e químicas, com três repetições e microbiológicas, com cinco repetições, dos produtos, logo após o tecnologia e por 2, 4, 6 e 8 semanas de armazenamento refrigerado (3ºC). A análise sensorial foi realizada nos tempos de 0 e 4 semanas, com uma repetição. Os resultados indicaram que houve diferença significativa de 5% (p≤0,05) nos carboidratos, proteínas, cinzas, acidez total titulável e na cromaticidade entre a cenoura in natura e a cenoura processada por tecnologia sous vide no tempo 0. Nos tempos de 2, 4, 6 e 8 semanas de armazenamento a 3ºC houve diferença significativa (p≤0,05) apenas nas proteínas e acidez total titulável. Na análise sensorial, não houve diferença significativa (p≤0,05) em nenhum dos atributos estudado. Observou-se também que a tecnologia sous vide foi eficiente na eliminação de células vegetativas de micro-organismos deteriorantes e patogênicos, porém não foi capaz de eliminar esporos. A cenoura processada por tecnologia sous vide conservou suas características nutricionais, sensoriais, químicas e manteve-se estável microbiologicamente até oito semanas de armazenamento à 3ºC.

In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.