Nas últimas décadas a soldagem em estado sólido vem se demonstrando como uma ótima alternativa perante os métodos tradicionais de união, os quais envolvem fusão dos materiais. O presente trabalho avalia a aplicação de um novo processo de união em estado sólido, a soldagem híbrida por difusão através de fricção (Hybrid Friction Diffusion Bonding - HFDB). O HFDB pode ser utilizado na união entre chapas finas ou também de chapas finas em substratos de materiais similares ou dissimilares. Através de calor e pressão os mecanismos de difusão são ativados gerando a união entre os materiais. Uma variante do processo de HFDB padrão pode ser utilizada para a fabricação das uniões de tubos e flanges-tubo de trocadores de calor de tubo espiral produzidos em alumínio. Utilizando como materiais duas ligas de alumínio dissimilares da série 5XXX, as amostras foram soldadas e caracterizadas. Visando a aplicação industrial do HFDB, o processo foi desenvolvido e sua viabilidade foi avaliada através de testes de estanqueidade, resistência à tração e análise metalográfica. Em seguida, visou-se a otimização dos parâmetros de soldagem (rotação, força axial e tempo de processo). Através de técnicas estatísticas de projeto de experimentos (DoE) os três fatores foram avaliados por meios de ensaios de tração para maximizar a resposta, limite de resistência. Investigações posteriores relacionadas aos mecanismos de união foram realizadas por meio da medição dos parâmetros de resposta, análise em microscópio ótico, aquisição de temperatura, espectroscopia de energia dispersiva de raios-x (EDX) e análise em elementos finitos (FEA). A primeira e mais importante premissa, a produção de soldas livres de vazamento, foi atingida. Em seguida, através da análise de uma equação de regressão e gráficos de superfície o conjunto de parâmetros otimizado – 1500 min-1 de rotação, 3 kN de força axial e 30 segundos de tempo de processo - atingiu resultados equivalentes a 95% de resistência quando comparados ao material base. O presente trabalho mostra que o processo de HFDB é promissor para aplicações industriais e indica vantagens perante os métodos tradicionais de união utilizados hoje na fabricação de trocadores de calor de alumínio. / In past few decades solid state welding has been demonstrating to be a great alternative compared to the traditional joining methods, which involve melting of the materials. This study evaluates the application of a new soliid state joining process called Hybrid Friction Diffusion Bonding (HFDB). The HFDB can be used to join thin plates or thin plates on substrates of similar or dissimilar materials. Through heat and pressure diffusion mechanisms are activated generating the bonding between the materials. A variant of the standard HFDB process can be used to manufacture tubes and tube-sheets of Coil-Wound Heat Exchangers made of aluminum. Using two dissimilar aluminum alloys from the 5XXX series, the samples were welded and characterized. Intending an industrial application of the HFDB, the process was developed and its feasibility was assessed by leak tightness tests, tensile strength tests and metallographic analysis. Subsequently, it was aimed to optimize the welding parameters (speed, axial force and process time). Through statistical analysis of design of experiments (DoE), the three factors were evaluated by tensile tests to maximize the response, ultimate tensile stress. Further investigation related to bonding mechanisms were carried out by measuring the response parameters, optical microscope analysis, temperature acquisition, energy dispersive x-ray spectroscopy (EDX) and finite element analysis (FEA). The first and most important target, the production of leakage free welds was achieved. Then, through the analysis of a regression equation and surface plots, the optimized parameter set – 1500 min-1 of rotational speed, 3kN of Axial force and 30 seconds of process time - achieved 95% of resistance when compared to the base material. This study shows that the HFDB process is very promising for industrial applications and indicates advantages compared to the traditional joining methods used today to manufacture aluminum heat exchangers.

Nas últimas décadas a soldagem em estado sólido vem se demonstrando como uma ótima alternativa perante os métodos tradicionais de união, os quais envolvem fusão dos materiais. O presente trabalho avalia a aplicação de um novo processo de união em estado sólido, a soldagem híbrida por difusão através de fricção (Hybrid Friction Diffusion Bonding - HFDB). O HFDB pode ser utilizado na união entre chapas finas ou também de chapas finas em substratos de materiais similares ou dissimilares. Através de calor e pressão os mecanismos de difusão são ativados gerando a união entre os materiais. Uma variante do processo de HFDB padrão pode ser utilizada para a fabricação das uniões de tubos e flanges-tubo de trocadores de calor de tubo espiral produzidos em alumínio. Utilizando como materiais duas ligas de alumínio dissimilares da série 5XXX, as amostras foram soldadas e caracterizadas. Visando a aplicação industrial do HFDB, o processo foi desenvolvido e sua viabilidade foi avaliada através de testes de estanqueidade, resistência à tração e análise metalográfica. Em seguida, visou-se a otimização dos parâmetros de soldagem (rotação, força axial e tempo de processo). Através de técnicas estatísticas de projeto de experimentos (DoE) os três fatores foram avaliados por meios de ensaios de tração para maximizar a resposta, limite de resistência. Investigações posteriores relacionadas aos mecanismos de união foram realizadas por meio da medição dos parâmetros de resposta, análise em microscópio ótico, aquisição de temperatura, espectroscopia de energia dispersiva de raios-x (EDX) e análise em elementos finitos (FEA). A primeira e mais importante premissa, a produção de soldas livres de vazamento, foi atingida. Em seguida, através da análise de uma equação de regressão e gráficos de superfície o conjunto de parâmetros otimizado – 1500 min-1 de rotação, 3 kN de força axial e 30 segundos de tempo de processo - atingiu resultados equivalentes a 95% de resistência quando comparados ao material base. O presente trabalho mostra que o processo de HFDB é promissor para aplicações industriais e indica vantagens perante os métodos tradicionais de união utilizados hoje na fabricação de trocadores de calor de alumínio. / In past few decades solid state welding has been demonstrating to be a great alternative compared to the traditional joining methods, which involve melting of the materials. This study evaluates the application of a new soliid state joining process called Hybrid Friction Diffusion Bonding (HFDB). The HFDB can be used to join thin plates or thin plates on substrates of similar or dissimilar materials. Through heat and pressure diffusion mechanisms are activated generating the bonding between the materials. A variant of the standard HFDB process can be used to manufacture tubes and tube-sheets of Coil-Wound Heat Exchangers made of aluminum. Using two dissimilar aluminum alloys from the 5XXX series, the samples were welded and characterized. Intending an industrial application of the HFDB, the process was developed and its feasibility was assessed by leak tightness tests, tensile strength tests and metallographic analysis. Subsequently, it was aimed to optimize the welding parameters (speed, axial force and process time). Through statistical analysis of design of experiments (DoE), the three factors were evaluated by tensile tests to maximize the response, ultimate tensile stress. Further investigation related to bonding mechanisms were carried out by measuring the response parameters, optical microscope analysis, temperature acquisition, energy dispersive x-ray spectroscopy (EDX) and finite element analysis (FEA). The first and most important target, the production of leakage free welds was achieved. Then, through the analysis of a regression equation and surface plots, the optimized parameter set – 1500 min-1 of rotational speed, 3kN of Axial force and 30 seconds of process time - achieved 95% of resistance when compared to the base material. This study shows that the HFDB process is very promising for industrial applications and indicates advantages compared to the traditional joining methods used today to manufacture aluminum heat exchangers.

Nas últimas décadas a soldagem em estado sólido vem se demonstrando como uma ótima alternativa perante os métodos tradicionais de união, os quais envolvem fusão dos materiais. O presente trabalho avalia a aplicação de um novo processo de união em estado sólido, a soldagem híbrida por difusão através de fricção (Hybrid Friction Diffusion Bonding - HFDB). O HFDB pode ser utilizado na união entre chapas finas ou também de chapas finas em substratos de materiais similares ou dissimilares. Através de calor e pressão os mecanismos de difusão são ativados gerando a união entre os materiais. Uma variante do processo de HFDB padrão pode ser utilizada para a fabricação das uniões de tubos e flanges-tubo de trocadores de calor de tubo espiral produzidos em alumínio. Utilizando como materiais duas ligas de alumínio dissimilares da série 5XXX, as amostras foram soldadas e caracterizadas. Visando a aplicação industrial do HFDB, o processo foi desenvolvido e sua viabilidade foi avaliada através de testes de estanqueidade, resistência à tração e análise metalográfica. Em seguida, visou-se a otimização dos parâmetros de soldagem (rotação, força axial e tempo de processo). Através de técnicas estatísticas de projeto de experimentos (DoE) os três fatores foram avaliados por meios de ensaios de tração para maximizar a resposta, limite de resistência. Investigações posteriores relacionadas aos mecanismos de união foram realizadas por meio da medição dos parâmetros de resposta, análise em microscópio ótico, aquisição de temperatura, espectroscopia de energia dispersiva de raios-x (EDX) e análise em elementos finitos (FEA). A primeira e mais importante premissa, a produção de soldas livres de vazamento, foi atingida. Em seguida, através da análise de uma equação de regressão e gráficos de superfície o conjunto de parâmetros otimizado – 1500 min-1 de rotação, 3 kN de força axial e 30 segundos de tempo de processo - atingiu resultados equivalentes a 95% de resistência quando comparados ao material base. O presente trabalho mostra que o processo de HFDB é promissor para aplicações industriais e indica vantagens perante os métodos tradicionais de união utilizados hoje na fabricação de trocadores de calor de alumínio. / In past few decades solid state welding has been demonstrating to be a great alternative compared to the traditional joining methods, which involve melting of the materials. This study evaluates the application of a new soliid state joining process called Hybrid Friction Diffusion Bonding (HFDB). The HFDB can be used to join thin plates or thin plates on substrates of similar or dissimilar materials. Through heat and pressure diffusion mechanisms are activated generating the bonding between the materials. A variant of the standard HFDB process can be used to manufacture tubes and tube-sheets of Coil-Wound Heat Exchangers made of aluminum. Using two dissimilar aluminum alloys from the 5XXX series, the samples were welded and characterized. Intending an industrial application of the HFDB, the process was developed and its feasibility was assessed by leak tightness tests, tensile strength tests and metallographic analysis. Subsequently, it was aimed to optimize the welding parameters (speed, axial force and process time). Through statistical analysis of design of experiments (DoE), the three factors were evaluated by tensile tests to maximize the response, ultimate tensile stress. Further investigation related to bonding mechanisms were carried out by measuring the response parameters, optical microscope analysis, temperature acquisition, energy dispersive x-ray spectroscopy (EDX) and finite element analysis (FEA). The first and most important target, the production of leakage free welds was achieved. Then, through the analysis of a regression equation and surface plots, the optimized parameter set – 1500 min-1 of rotational speed, 3kN of Axial force and 30 seconds of process time - achieved 95% of resistance when compared to the base material. This study shows that the HFDB process is very promising for industrial applications and indicates advantages compared to the traditional joining methods used today to manufacture aluminum heat exchangers.

No / The transient liquid phase bonding process has long been dealt with as a pure diffusion process at the joint interface, that is, as a mass phenomenon. In spite of the advances in the application of this technique to bond complex engineering alloys, the available models have failed to incorporate the effect of surface phenomena on the joining process. In this work, a new reaction–controlled diffusion formulation model is proposed, and the observation of experimental results of joining Al6061 alloy using thin single (50, 100 micron) and double Cu foils is recorded. This work directly unveils the unique role played by surface reaction–controlled diffusion rather than purely mass diffusion bonding process. Our experimental and modeling results reveal a conceptually new understanding that may well explain the joint formation in TLP bonding process.

Un nouveau concept d'échangeur de chaleur compacte est développé afin d’améliorer les performances du système de conversion d'énergie pour le réacteur ASTRID. La fabrication de géométries complexes (canaux rectangulaires millimétriques) est possible grâce au procédé de soudage diffusion : des tôles rainurées en acier inoxydable 316L sont empilées en conteneur et soudées lors d'un cycle de Compaction Isostatique à Chaud (CIC). La problématique est alors d'obtenir des interfaces résistantes tout en limitant la déformation des canaux nuisible à l’efficacité de l’échangeur. Pour arriver au meilleur compromis, les travaux de cette thèse vont aider à l’optimisation des paramètres pression/temps/température du cycle de CIC.Le premier axe de travail porte sur la simulation numérique de la déformation d’un tel échangeur lors de la CIC. L’influence des paramètres numériques (taille des éléments, critère de convergence) a été étudiée afin d’optimiser la précision et la vitesse des calculs. Les simulations ont mis en évidence l’importance des défauts d’empilements de la structure (glissements et ondulations des tôles) dans l’augmentation de la déformée de l’échangeur. Puis une caractérisation mécanique poussée des tôles laminées a mené à l’identification d’une loi de comportement entre 20°C à 1040°C.Le second axe porte sur la modélisation de l'évolution des interfaces lors du soudage diffusion et la prédiction de la tenue mécanique de ces dernières, l'ensemble pouvant mener à la définition d'un critère de validité des interfaces.Une étude microstructurale et mécaniques des interfaces a permis d’établir une corrélation entre la tenue mécanique d’un joint soudé-diffusé et son taux de surface soudée. En effet, la disparition de la porosité résiduelle est le critère principal pour obtenir de bonnes propriétés mécaniques à l’interface. Toutefois, le franchissement de l’interface par les joints de grains, est nécessaire pour retrouver les propriétés des tôles laminées. Un modèle analytique de fermeture des porosités (Hill et Wallach) est utilisé pour calculer le taux de surface soudée d’une interface en fonction des paramètres du cycle de CIC en modélisant la contribution des mécanismes (visco)plastique et diffusifs (en surface et au joint). Associé à la corrélation entre tenue mécanique et taux de surface soudée, il permet de proposer un outil prédictif pour la tenue mécaniques des interfaces soudé-diffusées. / A new concept of compact plate heat exchanger is developed for the energy conversion system performances of the ASTRID reactor. Manufacturing the complex geometry is possible by a diffusion-welding process: engraved 316L stainless steel plates are stacked and bonded during a Hot Isostatic Pressing cycle (HIP). The problematic is to get strong interfaces without deforming the channels which is harmful for the exchanger efficiency. To reach a good compromise, this thesis work will help to optimize the HIP parameters (pressure/temperature/ time).The first line of work is about the simulation of the heat exchanger deformation along manufacturing process. The influence of numerical parameters (elements size, convergence criterion) was studied to optimize the accuracy and the calculation time. Simulations have shown the importance of structure stack faults (sliding and plate ripples) in the increase of exchanger deformation. Then, a mechanical characterisation of plates was carried out to identify the constitutive equation between 20°C and 1040°C.The second line is about the interface modelling along welding and the prediction of their mechanical strength, as a whole can lead to the definition of an interface acceptability criterion. A microstructural and mechanical study has enabled to correlate the mechanical strength of a diffusion-bonded junction and its bonded area. Indeed, residual porosity disappearance is the main criterion to get good interfaces mechanical strength. However, the grain boundary migration is required to reach the rolled material properties. A void closure analytical model (Hill and Wallach) was used to estimate the bonded area of an interface according to HIP cycle parameters by modelling the contribution of (visco)plastic and diffusion (surface and boundary) mechanisms. Associated with the correlation between mechanical strength and the fraction of bonded area, it enables to propose a predictive tool for the mechanical strength of diffusion-bonded interfaces.

In this dissertation, the minimization of the diffusion bonding temperature during refractory metals’ diffusion bonding process was studied. Two pure refractory metals were used in this study: molybdenum and tungsten. The influence on the joint quality of molybdenum structural conditions, as well as molybdenum surface conditions, was examined. Moreover, diffusion bonding of tungsten to Oxygen Free Electrical copper and copper alloy (CuCr1Zr), without using an interlayer but instead using different bonding parameters, was evaluated. Diffusion bonding of tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy using titanium and nickel together as intermediate layers was also investigated, as well as the diffusion bonding of tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy using only nickel as an intermediate layer. The resulting joints were evaluated using optical microscopy, SEM, hardness, shear, and tensile tests. The residual stresses, as well as the deformation, that are generated due to the diffusion bonding process were evaluated through a FEM simulation using the software ANSYS. For pure molybdenum joints, successful results in minimizing bonding temperature were obtained. In tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy joints contrasting results were achieved. / In dieser Arbeit wurde ein Diffusionsschweißverfahren durchgeführt, um zwei Refraktärmetalle zu verbinden. Das erste war Molybdän, das ähnlich diffusionsgeschweißt ist. Das zweite war Wolfram, das diffusionsgeschweißt an OFE-Kupfer und an die CuCr1Zr-Legierung gebunden ist. Aufgrund der hohen Schmelztemperatur von Molybdän und Wolfram erforderten sie eine hohe Diffusionsschweißtemperatur. Das Hauptziel dieser Arbeiten ist es, die erforderliche Temperatur für den Verbindungsprozess zu reduzieren. Die Reduzierung der Molybdän Diffusions-schweißtemperatur ist abhängig von den Bedingungen der Molybdänoberfläche und -struktur. Die Verbindung von Wolfram mit OFE-Kupfer und mit CuCr1Zr-Legierungen erfolgte direkt (ohne Zwischenschicht) sowie unter Verwendung von Titan und Nickel als Zwischenschicht(en). Das Verbinden mit Zwischenschicht(en) ist abhängig von den Interaktionen zwischen der Zwischenschicht und den Grundwerkstoffen. Die Zwischenschichtenmetalle waren Reintitan und Reinnickel. Das Aufbringen der Zwischenschichten in den Verbindungen wurde als Wolfram - Titan - Nickel - Reinkupfer oder CuCr1Zr sortiert. Außerdem wurde nur reines Nickel als Zwischenschicht verwendet, um Wolfram mit Kupfer und der CuCr1Zr-Legierung zu verbinden. Die chemische Zusammenstellung der CuCr1Zr-Legierung ist in der Tabelle 1 dargestellt. Die Eigenspannungen sowie die Verformung, die durch den Diffusionsschweißprozess sowohl für die Refraktärmetalle Molybdän als auch Wolfram erzeugt werden, wurden durch einen Simulationsprozess mit dem Programm ANSYS bewertet. Die resultierenden Verbindungen wurden mittels Lichtmikroskopie, REM, Härte-, Scher- und Zugversuch bewertet. Die Eigenspannungen sowie die Verformung, die durch den Diffusionsschweißprozess erzeugt werden, wurden durch eine FEM-Simulation mit der Software ANSYS bewertet. Für reine Molybdänverbindungen wurden erfolgreiche Ergebnisse bei der Minimierung der Diffusionsschweißtemperatur erzielt. In Wolfram zu OFE-Kupfer und zu CuCr1Zr-Legierungsverbindungen wurden kontrastreiche Ergebnisse erzielt.