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This study relates the sensitization process microstructural changes of 5083-H116 to its resulting corrosion resistance and mechanical performance. Alcoa 5083-H116 was sensitized in an environmental chamber at 100°C for up to ~1500 hours and 150°C up to ~2000 hours, revealing different degrees of sensitization based on exposure times. Microstructural characterization was conducted on etched sensitized samples. Additionally, samples were subjected to accelerated corrosion scenarios for subsequent microstructural examination and subsequent mechanical (tension and tensile creep) testing. To connect the laboratory studies to the field exposure, Novelis 5083-H116 was sensitized at 100°C; dog bone samples were created and exposed for two years in a beach environment to investigate possible sensitization and corrosion effects. It was found that the sensitization at 100°C and 150°C of Alcoa 5083-H116 led to recrystallization from the asreceived (AR) state of the material (3 mg/cm²). The degree of sensitization of 61 mg/cm² recrystallized the grain size the most from the AR state. The higher sensitization temperature of 150°C caused higher thickness loss and mass-loss rates (MR) for the intergranular corrosion (IGC) susceptible sensitization levels. Accelerated corrosion on different surface orientations led to different corrosion mechanisms (parallel IGC vs. perpendicular IGC). While 5083-H116 material corroded on the rolled surface led to a uniform exfoliation damage on 150°C sensitization exposure, the 100°C rolled surface only exhibited pitting corrosion damage. The through plate thickness corrosion damage, however, exhibited a corrosion susceptible-resistant-susceptible (CSRS) pattern. Mechanical properties were assessed for the various conditions in terms of room temperature tension testing and elevated temperature creep tests. Sensitization affected yield strength but did not play a role in ultimate tensile strength. The presence of corrosion damage lowered yield strength and ultimate tensile strength of the IGC susceptible sensitized 5083-H116, with the through thickness corrosion damage reducing the properties more than corrosion of the rolled surface. Material sensitized at 150°C and then corroded had a greater reduction in room temperature mechanical properties. Creep testing was performed at elevated temperatures, and it was found the solely sensitized 5083-H116 at 100°C or 150°C behaved the same as as-received 5083-H116. When corrosion damage was introduced, creep rupture times and secondary creep rates were changed. Once the corroded section area was accounted for, no significant difference in Larson-Miller parameters was observed. / Ph. D. / Aluminum is frequently replacing steel in the hulls of U.S. and Australians naval ships. It is preferred because of its lower density than steel and higher corrosion resistance which reduces the need to paint topside surfaces. However, when aluminum alloys that are used in ship construction are exposed to elevated temperatures, the corrosion resistance ca be considerably decreased. Furthermore, fire resistance is always a concern on naval ships. Accordingly, we are interested in predicting how aluminum ships that may have previously corroded respond to fires. In this study, a laboratory technique was used to speed up the corrosion process of these ship hull aluminum alloys. Some samples were thermally exposed in the laboratory for microscopic analysis, corrosion testing, and subsequent mechanical testing. To connect the laboratory studies to the field exposure, thermally exposed samples were placed on a beach for two years to investigate further environmental damages. It was found that the laboratory thermal exposure weakened the aluminum alloy. The thermally exposed alloys were weakened to the corrosion process. Different surfaces of the thermally exposed plates had different corrosion damage mechanisms. Mechanical properties were assessed for the various conditions in terms of room temperature tension testing and elevated temperature creep tests. Thermal exposure affected yield strength (the ability of the material to stretch) but did not play a role in ultimate tensile strength (maximum strength prior to breaking). The presence of corrosion damage lowered yield strength and ultimate tensile strength of the corrosion susceptible thermally exposed alloy. Creep testing (constant applied stress testing) was performed at elevated temperatures (representative of fire damage scenarios), and it was found that the solely thermally exposed alloy behaved the same as as-received alloy in terms of failure mechanisms. When corrosion damage was introduced, creep rupture times (time until material fails by breaking into two pieces) was reduced. Once the corrosion damage was accounted for, mechanical properties could be more accurately represented, and failure times (conditions in the alloy needs to be replaced on ships) were predicted for the alloy.

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 description available.