A soldagem por fricção (Friction Stir Welding - FSW) é um processo eficiente de unir ligas de alumínio de alta resistência evitando defeitos que são usualmente criados quando técnicas convencionais de soldagem são utilizadas. A indústria aeronáutica tem mostrado grande interesse neste método de soldagem, tanto para a união de ligas similares como dissimilares. Entretanto, este processo causa modificações microestruturais dependentes das condições de tratamento térmico ou termomecânico. Contato elétrico entre zonas de microestruturas diferentes, por sua vez, pode resultar em acoplamento galvânico. No presente estudo, a soldagem por FSW foi usada para unir duas ligas de alumínio dissimilares, AA2024-T3 e AA7475-T651 e o efeito desta soldagem na resistência à corrosão das juntas soldadas e na microestrutura das ligas foi avaliada. Na investigação da resistência à corrosão foram utilizados ensaios eletroquímicos, especificamente, medidas de potencial de circuito aberto (OCP) em função do tempo de exposição ao meio corrosivo, ensaios de polarização e de espectroscopia de impedância eletroquímica, global (EIS) ou local (LEIS), em duas soluções, seja 0,1 M Na2SO4 ou 0,1 M Na2SO4 + 1 mM NaCl. Os ensaios eletroquímicos evidenciaram efeito de acoplamento galvânico nas juntas soldadas. A caracterização microestrutural foi realizada por microscopia ótica, microscopia eletrônica de varredura, microscopia eletrônica de transmissão e por calorimetria diferencial. As zonas afetadas pela solda tiveram importantes modificações na microestrutura indicadas pela precipitação e dissolução de precipitados que afetam a resistência à corrosão localizada. A resistência à corrosão intergranular e a resistência à esfoliação das juntas soldadas também foram avaliadas e comparadas com as das ligas AA2024-T3 e AA7475-T651 não soldadas. Os resultados mostraram aumento da suscetibilidade das juntas soldadas a estas formas de corrosão em comparação com as ligas não soldadas sendo observado ataque mais severo na liga AA7475-T651. A identificação das áreas anódicas e catódicas resultantes do acoplamento galvânico nas juntas soldadas foi realizada por teste que consistiu na deposição de camada de gel (ágar-ágar) com indicador universal na superfície das ligas soldadas. A liga AA2024-T3 atuou como cátodo, enquanto a AA7475-T651, como ânodo no par galvânico. Além disso, evolução de hidrogênio foi observada na região de interface entre a zona termomecanicamente afetada e a termicamente afetada da liga AA7475-T651 mostrando que reações catódicas também ocorreram localmente nesta última liga. Resultados de LEIS obtidos nas diferentes zonas das duas ligas soldadas por FSW mostraram acoplamento galvânico na interface entre elas para tempos curtos de ensaio e deslocamento da região mais ativa com o tempo de ensaio para a liga AA7475-T651, mais precisamente para a interface entre a zona termomecanicamente afetada e a térmicamente afetada desta liga. / Friction Stir Welding (FSW) is an efficient process of joining high strength aluminum alloys avoiding defects that are usually created when conventional welding techniques are used. The aircraft industry has shown great interest in this welding method, both for welding of similar or dissimilar alloys. However, this process causes microstructural changes that are dependent on the thermal or thermomechanical conditions applied. Electrical contact between zones of different microstructures, in turn, can result in galvanic coupling. In the present study, FSW was used to join two dissimilar aluminum alloys, AA2024-T3 and AA7475-T651 and the effect of this process on the corrosion resistance of the welded joints and on the microstructure of the alloys was evaluated. For corrosion resistance evaluation, electrochemical tests were used, specifically, open circuit potential measurements (OCP) as a function of time of exposure time to the corrosive environment, polarization tests, and electrochemical impedance spectroscopy, global (EIS) or local (LEIS), in two solutions, either 0.1 M Na2SO4 or 0.1M Na2SO4 + 1 mM NaCl. The electrochemical tests showed galvanic coupling effects in the welded joints. Microstructural characterization was carried out by optical microscopy, scanning electron microscopy, transmission electron microscopy and differencial scanning calorimetry. The welded affected zones showed significant microstructural changes indicated by precipitation and dissolution of precipitates that affect the localized corrosion resistance. Intergranular and exfoliation corrosion resistance of the welded joints were also evaluated and compared to those of unwelded AA2024-T3 and AA7475-T651 alloys. The results showed increased susceptibility of welded joints to these forms of corrosion in comparison with the unwelded alloys with more severe attack associated to the AA7475-T651 alloy. Identification of anodic and cathodic areas due to galvanic coupling in the welded joints was evaluated by a test consisting in depositing a gel layer (ágar-ágar) with universal indicator on the surface of the welded alloys. The AA2024-T3 alloy worked as cathode, while the AA7475-T651 as anode in the galvanic coupling. Furthermore, hydrogen evolution was observed at the interface region between the thermomechanically affected zone and the heat affected alloy AA7475-T651 showing that cathodic reactions also occurred on this last alloy. LEIS results obtained in different zones of the two FSW welded alloys showed galvanic coupling at the interface between them for short test times and displacement of the most active region to the AA7475-T651 alloy, at longer periods of test, specifically to the interface between the thermomechanically affected and the heat affected zones of this last alloy.

The Friction Stir Welding (FSW) process has been under constant developmentsince its invention, more than 20 years ago. Whereas most industrial applicationsuse a gantry machine to weld linear joints, there are applications which consistof complex three-dimensional joints, requiring more degrees of freedom fromthe machines. The use of industrial robots allows FSW of materials alongcomplex joint lines. There is however one major drawback when using robotsfor FSW: the robot compliance. This results in vibrations and insufficient pathaccuracy. For FSW, path accuracy is important as it can cause the welding toolto miss the joint line and thereby cause welding defects.The first part of this research is focused on understanding how welding forcesaffect the FSW robot accuracy. This was first studied by measuring pathdeviation post-welded and later by using a computer vision system and laserdistance sensor to measure deviations online. Based on that knowledge, a robotdeflection model has been developed. The model is able to estimate thedeviation of the tool from the programmed path during welding, based on thelocation and measured tool forces. This model can be used for online pathcompensation, improving path accuracy and reducing welding defects.A second challenge related to robotic FSW on complex geometries is thevariable heat dissipation in the workpiece, causing great variations in the weldingtemperature. Especially for force-controlled robots, this can lead to severewelding defects, fixture- and machine damage when the material overheats.First, a new temperature method was developed which measures thetemperature at the interface of the tool and the workpiece, based on the thermoelectriceffect. The temperature information is used as input to a closed-looptemperature controller. This modifies primarily the rotational speed of the tooland secondarily the axial force. The controller is able to maintain a stablewelding temperature and thereby improve the weld quality and allow joining ofgeometries which were impossible to weld without temperature control.Implementation of the deflection model and temperature controller are twoimportant additions to a FSW system, improving the process robustness,reducing the risk of welding defects and allowing FSW of parts with highlyvarying heat dissipation.

<p>Solid state Friction stir welding (FSW) is of major interest in the welding of aluminium since it improves the joint properties. Many applications where Al-alloys are used are subject to varying load conditions, making fatigue failure a critical issue. In the scope of this thesis, the fatigue performance of friction stir welded AlMgSi-alloy 6082 has been investigated. Static and dynamic properties of different joint configurations and welds produced with varying process parameters have been determined. Microstructures of fractured surfaces have been studied to evaluate the effect of weld discontinuities on fatigue. The mechanical strength of the friction stir welds was set in relation to that of conventional fusion welds, and that of other FS welded Al-alloys.</p><p>The friction stir process produced aluminium butt welds with high and consistent fatigue strengths, which exceeded the strengths of similar fusion welded samples. A smooth weld geometry showed to be of great importance for the fatigue performance, favouring the friction stir welds. Welding speed in a tested range of 0.35-1.4 m/min had only a modest influence on the properties of the friction stir welds; properties were not deteriorating at the highest speed. The softening of the alloy around the weldline was modelled. A fair description of the hardness profiles across the weld was obtained. At a low and high welding speed a full and partial softening respectively was predicted, indicating that full softening is not required to obtain a flawless weld.</p><p>In case of friction stir overlap welds, tool design is even more important than in butt welding to secure weld quality. A broad tool shoulder with a concave pin end gave the best performance. In particular, the minimal influence on the sheet interface when welding with such a tool was beneficial for the fatigue strength. The stress distribution in overlap and T-type test specimens has been modelled. The stress intensity factors were determined. The corresponding crack propagation rates were in fair accordance with the experimental results. It was found that a simplified approach, developed to estimate ∆K for overlap spot welds, could be used also for friction stir overlap joints.</p>

Multi-material structures are increasingly used in vehicle bodies to reduce weight of cars. The use of these lightweight structures is driven by requirements to improve fuel economy and reduce CO2 emissions. The automotive industry has replaced conventional steel components by lighter metals such as aluminium alloy. This is done together with cutting weight of structures using more advanced strength steels. However, sound joining is still difficult to achieve due to differences in chemical and thermal properties.   This research aims to develop a new innovative welding technique for joining aluminium alloy to ultra-high strength steels. The technique is based on friction stir welding process while the non-consumable tool is made of an ordinary tool steel. Welding was done by penetrating the rotating tool from the aluminium side without penetrating into the steel surface. One grade of Al-Mg aluminium alloy was welded to ultra-high strength steels under lap joint configuration. Different types of steel surface coatings including uncoated, hot-dipped galvanised and electrogalvanised coating have been studied in order to investigate the influence of zinc on the joint properties. The correlation among welding parameters, microstructures, intermetallic formation and mechanical properties are demonstrated in this thesis.  Results have shown that friction stir welding can deliver fully strong joints between aluminium alloy and ultra-high strength steels. Two intermetallic phases, Al5Fe2 and Al13Fe4, were formed at the interface of Al to Fe regardless of surface coating conditions. The presence of zinc can improve joint strength especially at low heat input welding due to an increased atomic bonding at Al-Fe interface. The formation of intermetallic phases as well as their characteristics has been demonstrated in this thesis. The proposed welding mechanisms are given based on metallography investigations and related literature. / <p>QC 20170519</p>

This thesis is based on the PhD work of investigating the Friction Stir Welding process (FSW) with numerical and Artificial Neural Network (ANN) modelling methods. FSW was developed at TWI in 1991. As a relatively new technology it has great advantages in welding aluminium alloys which are difficult to weld with traditional welding processes. The aim of this thesis was the development of new modelling techniques to predict the thermal and deformation behaviour. To achieve this aim, a group of Gleeble experiments was conducted on 6082 and 7449 aluminium alloys, to investigate the material constitutive behaviour under high strainrate, near solidus conditions, which are similar to what the material experiences during the FSW process. By numerically processing the experimental data, new material constitutive constants were found for both alloys and used for the subsequent FSW modelling work. Importantly no significant softening was observed prior to the solidus temperature. One of the main problems with numerical modelling is determining the values of adjustable parameters in the model. Two common adjustable parameters are the heat input and the coefficients that describe the heat loss to the backing bar. To predict these coefficients more efficiently a hybrid model was created which involved linking a conventional numerical model to an ANN model. The ANN was trained using data from the numerical model. Then thermal profiles were abstracted (summarised) and used as inputs; and the adjustable parameters were used as outputs. The trained ANN could then use abstracted thermal profiles from welding experiments to predict the adjustable parameters in the model. The first stage involved developing a simplified FE thermal model which represents a typical welding process. It was used to find the coefficients that describe the heat loss to the backing bar, and the amount of power applied in the model. Five different thermal boundary conditions were studied, including both convective and ones that included the backing bar with a contact gap conductance. Three approaches for abstracting the thermal curves and using as inputs to the ANN were compared. In the study, the characteristics of the ANN model, such as the ANN topology and gradient descent method, were evaluated for each boundary condition for understanding of their influences to the prediction. The outcomes of the study showed that the hybrid model technique was able to determine the adjustable parameters in the model effectively, although the accuracy depended on several factors. One of the most significant effects was the complexity of the boundary condition. While a single factor boundary condition (e.g. constant convective heat loss) could be predicted easily, the boundary condition with two factors proved more difficult. The method for inputting the data into the ANN had a significant effect on the hybrid model performance. A small number of inputs could be used for the single factor boundary condition, while two factors boundary conditions needed more inputs. The influences from the characteristics of the ANN model were smaller, but again thermal model with simpler boundary condition required a less complex ANN model to achieve an accurate prediction, while models with more complex boundary conditions would need a more sophisticated ANN model. In the next chapter, the hybrid method was applied to a FSW process model developed for the Flexi-stir FSW machine. This machine has been used to analyse the complex phase changes that occur during FSW with synchrotron radiation. This unique machine had a complex backing bar system involving heat transfer from the aluminium alloy workpiece to the copper and steel backing bars. A temperature dependent contact gap conductance which also depends on the material interface type was used. During the investigation, the ANN model topologies (i.e. GFF and MFF) were studied to find the most effective one. Different abstracting methods for the thermal curves were also compared to explore which factors (e.g. the peak temperature in the curve, cooling slope of a curve) were more important to be used as an input. According to close matching between the simulation and experimental thermal profiles, the hybrid model can predict both the power and thermal boundary condition between the workpiece and backing bar. The hybrid model was applied to six different travel speeds, hence six sets of heat input and boundary condition factors were found. A universal set was calculated from the six outcomes and a link was discovered between the accuracy of the temperature predictions and the plunge depth for the welds. Finally a model with a slip contact condition between the tool and workpiece was used to investigate how the material flow behaviour was affected by the slip boundary condition. This work involved aluminium alloys 6082-T6 and 7449-T7, which have very different mechanical properties. The application of slip boundary condition was found to significantly reduce the strain-rate, compared to a stick condition. The slip condition was applied to the Flexi-stir FSW experiments, and the results indicated that a larger deformation region may form with the slip boundary condition. The thesis successfully demonstrates a new methodology for determining the adjustable parameters in a process model; improved understanding of the effect of slip boundary conditions on the flow behaviour during FSW and insight in to the behaviour of aluminium alloys at temperatures approaching the solidus and high strain-rates.

Friction Stir Welding (FSW) was used to perform Bead on Plate (BOP) welds on 6061-T6511 aluminum extrusions. Using a DOE approach, tool rotation speed, clamp spacing, and clamping force were altered to ascertain their effects on distortion in the welded panels. Mechanical forces were monitored during the weld process. Both linear and out of plane distortion were measured on the welded extrusions. The Vickers hardness of the weld nugget was measured. The effect of each parameter on weld distortion was discovered and the mechanism of this link was suggested.

A soldagem por atrito com pino não consumível (SAPNC), processo de união no estado sólido, tornou-se conhecido devido à alta resistência das juntas produzidas em comparação ao metal de base e aos métodos convencionais de união. No entanto, o próprio processo apresenta seus desafios, relacionados principalmente à combinação do efeito de geometrias de ferramenta com os parâmetros utilizados. O desenvolvimento de métodos de simulação numérica tem criado a possibilidade de otimização destes efeitos, prevendo as interações entre os materiais, parâmetros e geometrias de ferramenta com menor custo e tempo. O presente trabalho teve como objetivo simular o processo de soldagem por atrito utilizando método dos elementos finitos (MEF) no software DEFORM 3D e avaliar a capacidade do modelo em representar fenômenos presentes do processo, tais como esforços da ferramenta, ciclo termomecânico do material e microestrutura. O estudo foi realizado em amostras de uma chapa de liga de magnésio AZ31B. Para inclusão da evolução mecânica e microestrutural do material de estudo no modelo, dados foram obtidos pelo estudo da compressão isotérmica da liga AZ31 simulador termomecânico Gleeble, em condições típicas às encontradas no processo de soldagem por atrito em. Os dados de tensão, deformação e microestrutura obtidos nos ensaios de compressão foram tratados analiticamente afim de se obter os parâmetros para as equações de deformação à quente e evolução microestrutural do material de estudo. Ademais, na próxima etapa, utilizou-se um pino roscado e não roscado em soldagens dissimilares afim de analisar o efeito da geometria da ferramenta no fluxo de material. Para auxiliar a análise foram utilizadas técnicas de microscopia óptica, microscopia eletrônica de varredura (MEV) e difração de raios X. Por fim, um modelo numérico de soldagem por atrito elaborado no software DEFORM-3D é apresentado. Os resultados do modelo foram comparados com os resultados experimentais com auxílio de técnicas de caraterização microestrutural, EBSD, ciclos térmicos capturados por termopares e torque das ferramentas. Os resultados e conclusões obtidos no projeto permitiram a identificação do ciclo térmico, mecânico e microestrutural do material durante a soldam por atrito, além da demostração do efeito da geometria para distintos parâmetros de processo, indicando um método alternativo eficiente na otimização de geometrias de ferramenta e busca de parâmetro ótimos do processo de soldagem por atrito com tempo e custo reduzidos. / Friction stir welding (FSW), a solid-state process, has become known due to the high strength of the produced joints compared to the base metal and the conventional welding methods. However, the friction stir welding has its challenges, related with tools geometry and the process parameters. The development of numerical simulation methods has been able to aid in the process optimization, including the study of different materials, parameters and tool geometries with lower cost and time. The obejective of the present work is propose a friction stir welding numerical model through finite element analysis (FEA) in DEFORM 3D software and evaluated its capacity to represent the process features such as the tool chacteristics, the thermomechanical cycle of the material and its microstructure. The material chosen for the study was a magnesium alloy AZ31B. In order to include the mechanical and microstructural evolution of the study material in the model, data were obtained through isothermal compression of the AZ31 in Gleeble thermomechanical simulator, under typical conditions found in the friction welding process. Stress, strain and microstructure data obtained in the compression tests were analyzed analytically to obtain the parameters for the hot deformation equations and microstructural evolution of the material. Moreover, a threaded and non-threaded pin in dissimilar welds was used to verify the effect of tool geometry in the material flow during the friction stir welding process. The evaluation was made with the support of optical microscopy and scanning electron microscopy (SEM). Then, a numerical model of friction welding developed in the DEFORM-3D software is presented. The results of the model were compared with experimental results supported by microstructural characterization techniques, EBSD, temperature profiles captured by thermocouples and tool torque response. The results and conclusions obtained in the project allowed the identification of the thermal, mechanical and microstructural cycle of the material during the friction stir welding process, besides the demonstration of the effect of the tool geometry for different process parameters, indicating an efficient alternative method in the optimization of tool geometries and optimal parameter for the friction welding process with reduced time and cost.

A crescente escassez dos recursos energéticos renováveis, bem como o contínuo aumento dos seus custos tem requerido nas últimas décadas uma redução drástica no consumo de energia utilizada para o transporte de cargas e passageiros. A indústria siderúrgica pode contribuir decisivamente neste contexto, disponibilizando no mercado aços de maior resistência mecânica, os quais podem ser utilizados em estruturas mais esbeltas. Os aços com elevados teores de Mn (15-30%) representam um desenvolvimento muito recente de ligas ferrosas puramente austeníticas, que reúnem resistência mecânica elevada e grande ductilidade. Além disso, trata-se de ligas de baixo custo devido à eliminação dos elevados teores de Ni necessários para a estabilização da austenita e ao reduzido tempo de processamento, que dispensa tratamentos térmicos e processamentos termomecânicos controlados. Por outro lado, a redução de peso estrutural no setor automobilístico requer não somente a pesquisa de novos aços, mas também a utilização de componentes híbridos, resultantes, entre outros, da união dos aços austeníticos alto Mn com aços comerciais estruturais de alta resistência e baixa liga (ARBL). Nesta dissertação, estudou-se, portanto, a soldabilidade pelo processo de fricção e mistura mecânica (SFMM) de aço austenítico alto Mn com efeito TRIP (plasticidade induzida por transformação martensítica) com aço ARBL processado termomecanicamente tipo XABO500 (ThyssenKrupp Steel, limite de escoamento > 460 MPa). As placas de aço TRIP foram fabricadas na EESC-USP com composição Fe-22.5% Mn-0.4% C através de fundição sob atmosfera protetora de argônio, tratamento térmico de homogenização e laminação a quente a 1150°C. As juntas dissimilares TRIP-ARBL foram produzidas com chapas de 3.5 mm de espessura. Os ensaios de soldagem SFMM foram conduzidos com ferramenta de compósito PCBN-WRe. O aporte térmico de soldagem foi variado através do uso de três velocidades de rotação da ferramenta: 300, 400 e 500 rpm, e o avanço foi de 100 mm/min. Dois deslocamentos (offsets) da ferramenta foram investigados: +1.0 e +2.0 mm em direção ao aço TRIP. Os resultados revelaram um acabamento superficial satisfatório das juntas soldadas com 300 e 400 rpm. A penetração de soldagem aumentou com a velocidade de rotação da ferramenta e com um maior deslocamento da ferramenta em direção ao aço TRIP devido ao crescimento do aporte térmico. A SFMM produziu em ambos os lados das juntas dissimilares uma microestrutura caracterizada apenas por zona de mistura (ZM) e zona termicamente afetada (ZTA), não sendo observada a formação de zonas termomecanicamente afetadas (ZTMA). Na ZM do aço ARBL, a SFMM produziu uma microestrutura polifásica, contendo misturas de ferrita acicular, bainita e martensita. O lado TRIP da ZM não exibiu sinais de transformação martensítica induzida por deformação e sofreu recristalização dinâmica com a formação de uma austenita refinada em comparação com o metal de base. A junta produzida com menor aporte térmico (300 RPM e Offset +1) apresentou os maiores picos de dureza na ZM do aço TRIP devido à maior taxa de resfriamento e, consequentemente, a microestrutura mais fina. Apesar dos maiores picos de dureza, a junta produzida com 300 RPM e Offset +1 apresentou o melhor desempenho no ensaio de tração, atingindo o maior percentual de alongamento a fratura e rompendo no metal de base ARBL. Isso se deve provavelmente à formação de ferrita acicular mais fina na ZM do aço ARBL com microestrutura entrelaçada e de maior tenacidade, se comparado com o metal de base ARBL. / The increasing scarcity of renewable energy resources and their continuously rising costs have required in the last decades a drastic reduction in the energy consumption for the transportation of goods and passengers. The steel industry can decisively contribute in this context by providing the market with steel grades of increased mechanical strength, which can be incorporated into light-weight structures. Steels with high Mn contents (15-30%) represent a recent development of austenitic ferrous alloys that combine elevated mechanical strength with high ductility. In addition, those steel grades correspond to low cost alloys due to the replacement of the high Ni contents necessary to stabilize the austenite as well as the reduced manufacturing time that does not involve subsequent heat treatments or controlled thermo-mechanical processing. On the other hand, the reduction of structural weight in the automotive sector does not only require the research on novel steels, but also the use of hybrid components that result among others from joining austenitic high-Mn steels to commercial structural high-strength low-alloyed (HSLA) steel grades. In this work, we studied therefore the friction stir weldability of an austenitic high-Mn steel with TRIP (transformation induced plasticity) effect to the thermomechanically processed HSLA XABO500 steel grade (ThyssenKrupp Steel, yield strength > 460 MPa). High-Mn TRIP steel plates were produced at the EESC-USP with the chemical composition of Fe-22.5% Mn-0.4% C by casting under protective argon atmosphere, followed by homogenization treatment and hot rolling at 1150°C. The dissimilar TRIP-HSLA joints were produced using 3.5 mm thick plates. The friction stir welding (FSW) experiments were carried out with a tool made of a PCBN-WRe composite. The heat input was varied by using three tool rotational speeds: 300, 400 and 500 rpm. The welding speed was set to 100 mm/min. Two different tool offsets were investigated: +1.0 and +2.0 mm towards the high-Mn TRIP steel. The results revealed that a satisfactory surface finishing is achieved for the butt-joints produced with 300 and 400 rpm. The welding penetration increased for higher tool rotational speeds and larger tool offsets towards the TRIP steel because of an increased heat input. FSW produced at both sides of the dissimilar joints a microstructure characterized by only stir zone (SZ) and heat-affected zone (HAZ). Thermo-mechanical affected zones (TMAZ) could not be observed. In the SZ of the HSLA steel, FSW produced a multiphase microstructure that contains a mixture of acicular ferrite, bainite and martensite. The TRIP side of the SZ did not exhibit traces of strain induced martensitic transformation and underwent dynamic recrystallization with the formation of a fine-grained austenite in comparison to the base material. The butt-joint produced with the lowest heat input (300 RPM and Offset +1) developed the highest hardness peaks in the SZ of the TRIP steel because of the increased cooling rate and, consequently, the more refined microstructure. In spite of the hardest zones, the butt-joint produced with 300 RPM and offset +1 achieved the best performance in the tensile tests by reaching the largest elongation to fracture and having the failure in the HSLA base material. This is likely promoted by the formation of a more refined acicular ferrite in the SZ of the HSLA steel with interpenetrated microstructure and enhanced toughness in comparison to the HSLA base material.

Este trabalho apresenta um modelo inovador de coletor solar plano, com placa absorvedora fabricada por Estampagem Incremental e Soldagem FSW (Friction Stir Welding). Esta placa absorvedora é constituída de duas chapas de alumínio AA1200-H14 com espessura de 1 mm, estampadas e soldadas em simetria, a fim de que na união das chapas sejam deixados canais para passagem de água. Neste estudo foi realizada a caracterização do material por Ensaio de Tração e Ensaio Nakajima. Para determinação dos parâmetros de Estampagem Incremental foram realizados 16 experimentos com ferramenta de diâmetro df = 9,5 mm, variando a rotação de N = 50 rpm a 800 rpm e o incremento vertical de Δz = 2 mm a 0,2 mm, mantendo o avanço em = 250 mm/min. E também foram realizados 3 experimentos com ferramenta df = 22 mm, variando o incremento vertical de Δz = 2 mm a 0,5 mm, mantendo a rotação em N = 50 rpm e o avanço em = 250 mm/min. Para determinação dos parâmetros de Soldagem FSW foram realizados 4 experimentos com ferramenta de ombro de diâmetro 8 mm e pino roscado M3x0,5, mantendo a rotação em N = 1500 rpm e variando o avanço entre = 100 mm/min a 400 mm/min. Em seguida foi fabricado um protótipo de placa absorvedora de coletor solar com área de 0,12 m². Nos experimentos realizados foi constatado que é possível obter maiores deformações na Estampagem Incremental do que na Estampagem Convencional e que as deformações são mais elevadas quando se utiliza menores diâmetros, maiores rotações e menores incrementos verticais da ferramenta. Na Soldagem FSW não foi constatada influência na qualidade do cordão de solda em relação à variação do avanço da ferramenta. Neste estudo também se verificou que é possível fabricar protótipos de placas absorvedoras de coletores solares pelos processos de Estampagem Incremental e Soldagem FSW. No entanto, para coletores em tamanho comercial, novos estudos são necessários para melhorar a forma de fixação das chapas durante a Soldagem FSW. / This work presents an innovative model of flat plate solar collector, with absorber plate manufactured using Incremental Sheet Forming (ISF) and Friction Stir Welding (FSW). This absorber plate consists of two AA1200-H14 aluminum sheets with a thickness of 1 mm, stamped and welded in symmetry, in order to leave channels for the passage of water. In this study the characterization of the material by Nakajima Test and Traction Test was performed. In order to determine the parameters of ISF, 16 experiments were performed with a tool of diameter df = 9.5 mm, varying the rotation speed of N = 50 rpm at 800 rpm and the step down of Δz = 2 mm to 0.2 mm, maintaining the feed rate at = 250 mm/min. Also, 3 experiments with tool df = 22 mm were performed, varying the step down of Δz = 2 mm to 0.5 mm, maintaining the rotation speed at N = 50 rpm and the feed rate at = 250 mm/min. For determination of FSW parameters, 4 experiments with 8 mm diameter shoulder tool and M3x0.5 pin were performed, maintaining the rotation speed at N = 1500 rpm and varying the feed rate from = 100 mm/min to 400 mm/min. A prototype solar collector absorber plate with a 0.12 m² area was then manufactured. In the experiments carried out, it was found that it is possible to obtain greater deformations in the ISF than in the Conventional Stamping and that the deformations are higher when using smaller diameters, higher rotations and smaller step downs of the tool. In FSW, no influence was observed in the quality of the weld bead in relation to the variation of the tool feed rate. In this study it was also verified that it is possible to manufacture prototypes of solar collector absorber plates by the processes of ISF and FSW. However, for commercial size collectors, further studies are needed to improve the way the plates are fixed during FSW.

Os aços inoxidáveis duplex são largamente utilizados na fabricação de equipamentos para a indústria de óleo e gás, utilizados tanto no ambiente onshore quanto offshore. Sua grande limitação é que, com o aumento de temperatura, ocorre precipitação de fases indesejáveis, que reduzem drasticamente a resistência à corrosão e as propriedades mecânicas desses materiais. Considerando o efeito deletério da soldagem a fusão nos aços inoxidáveis duplex, a soldagem por atrito com pino não-consumível (FSW) é amplamente considerada como alternativa aos processos convencionais. Como no FSW a união dos materiais ocorre no estado sólido, muitos dos problemas de soldabilidade associados às técnicas tradicionais de soldagem por fusão são evitados. Neste trabalho, amostras retiradas da zona misturada (ZM), das zonas afetadas pelo calor (ZTA e ZTMA) e do metal de base (MB) de chapas de aço inoxidável lean duplex LDX 2404&reg (UNS S82441) soldadas por atrito com pino não-consumível foram caracterizadas microestruturalmente e tiveram sua resistência à corrosão avaliada por meio de ensaios eletroquímicos. Os resultados obtidos nos ensaios eletroquímicos indicaram que as zonas afetadas pelo calor e a ZM se mantiveram tão resistentes à corrosão localizada quanto o MB. Permitiram concluir também que a excelente resistência à corrosão da liga está associada ao teor elevado de N. / Duplex stainless steels have been widely used in the manufacture of equipments and piping for oil & gas industry, in onshore and offshore service. However, whenever they are exposed to high temperatures the precipitation of deleterious phases might occur. The precipitates drastically reduce the corrosion resistance and mechanical properties of these materials. The friction stir welding (FSW) process has been considered as an alternative to replace the conventional fusion welding processes in duplex stainless steels. FSW is a solid-state welding process avoiding many of the problems associated to conventional fusion techniques. In this study, specimens of the various zones affected and nearby the FSW, specifically the nugget or stir zone (SZ), the heat affected zones (HAZ/TMAZ) and the base metal (BM) of welded lean duplex UNS S82441 were characterized microstructurally and had their corrosion resistance evaluated by electrochemical tests. The results indicated that the HAZ/TMAZ and SZ regions presented similar localized corrosion resistance to that of the BM showing that it is a potential technique for replacing the conventional processes with advantageous corrosion resistance properties. They also concluded that the excellent corrosion resistance of the alloy is associated with the high N content.