A. F. Miranda Pérez

Effect of FSW Parameters on Microstructure of Aluminum Matrix Composites Joints

Automotive and aerospace industries are maintaining constant development and innovation, demanding for materials that can fulfill emissions, fuel efficiency, and security regulations. Recently, the interest in automotive applications of metal matrix composites (MMC) is increasing. MMC exhibits excellent mechanical properties such as wear and abrasion resistance, high strength, chemical stability, and dimensional stability to high temperatures. In order to join MMC, friction stir welding (FSW) appears as the most promising joining process compared with conventional fusion welding processes, mainly for the ability to join without compromising their ceramic reinforcements. The aim of this study was to evaluate the microstructural changes of diverse parameters of aluminum matrix reinforced with 20 % wt. Al/SiC composite was welded with different process parameters such as tool rotation speed and axial force using FSW. In order to determine the different microstructural zones characterization of the samples was carried out by optical microscopy (OM) and scanning electron microscopy (SEM). In addition, an evaluation of mechanical property such as microhardness of the different zones of the joint in the aluminum matrix composite samples was performed.

Wear Resistance Analysis of A359/SiC/20p Advanced Composite Joints Welded by Friction Stir Welding

O avanco no desenvolvimento de pecas automotivas exige novos materiais de baixo custo com propriedades mecânicas superiores e com maior resistencia ao desgaste em comparacao com os materiais existentes. Por exemplo, compositos com matriz de aluminio (AMC) mostram melhores propriedades mecânicas como resistencia a abrasao e ao desgaste, alta resistencia e estabilidade quimica e dimensional. A industria automotiva tem centrado em AMC para uma variedade de aplicacoes em pecas automotivas, a fim de melhorar a economia de combustivel, minimizar as emissoes dos veiculos, melhorar as opcoes de design e aumentar o desempenho. A Resistencia ao desgaste e um fator importante a determinar para a vida util dos componentes automotivos, em geral naqueles componentes submetidos a sistemas mecânicos como freios e suspensoes. O processo de soldagem por friccao e mistura mecânica (FSW - Friction Stir Welding) surge como um processo capaz de unir AMC, principalmente com a capacidade de soldar sem comprometer seu reforco cerâmico. O objetivo deste estudo e focado na analise de caracteristicas de desgaste da junta soldada por FSW de matriz de aluminio reforcados com 20 por cento em peso de composito de carboneto de silicio (A359 / SiC / 20p). O procedimento experimental consistiu em cortar amostras em pequenas placas e realizar tres soldas nestas placas utilizando uma maquina FSW com uma ferramenta com ombro de 20 mm de diâmetro e pino de 8 mm de diâmetro. As caracteristicas de desgaste das tres juntas soldadas e metal base foram analisados aplicando carga constante de 5 N e uma velocidade de rotacao de 100 rpm utilizando um aparelho de teste Pin-on-disk, usando uma esfera de aco de com safira com 6 mm de diâmetro. Os resultados experimentais indicam que as tres juntas soldadas apresentaram baixo coeficiente de friccao comparado com o metal base. Os resultados determinaram que os parâmetros do processo FSW afetam a resistencia ao desgaste das juntas soldadas, devido a diferentes modificacoes microestruturais durante a soldagem, que provoca uma baixa resistencia ao desgaste na zona soldada.

Geometry Tool Influence on the Microstructure of MMC Al-SiC Friction Stir Welds

Welding as a manufacturing process on aeronautical industry is necessary for component integration. In the aircraft manufacturing, the use of aluminum alloys is widely extended. However, in these alloys if fusion welding is applied, some microstructural alterations, deleterious phases, and distortion are presented and decrease the mechanical properties of the joint. The aluminum matrix composites (AMCs) present many advantages of traditional aluminum alloys; superior properties are achieved when ceramic particles are added making them suitable for aeronautic industry. The disadvantages for AMCs with fusion welding processes are: agglomeration of the particles, lack of fusion, porosity, and many other welding defects. Recently, the solid-state welding processes are gaining acceptance due to high-quality joints, defect-free, and environmental cleaner processes, mainly the friction stir welding (FSW). Hence, FSW is commonly employed for joining these materials, and many studies have been published where the tool is the principal subject; they are mainly focused in tool wear rather than geometry influence on microstructure. Therefore, this investigation was performed in order to observe the effects of geometry differences; the aim was to examine the microstructural evolution of the welded joints. Optical and scanning microscopes (OM and SEM) were employed for the evaluation, resulting in a partial grain refinement in the thermomechanical affected zone, for the aluminum matrix and eutectic silicon, and for the fracture of the silicon carbides. In addition, orientation imaging microscopy (OIM) using electron backscatter diffraction (EBSD) technique was employed to analyze the dynamic recrystallization. Some welding defects were presented along the joint for one tool. Finally, hardness Vickers evaluation on the joints was completed resulting in differences between the two employed tools.

Distortion Evaluation in Dissimilar Stainless Steel Joints Welded by GMAW Process

Manufacturing in almost all industries involves joining together many components. Welding is the most popular joining process, which is cost effective, reliable, and versatile. In the automobile industry, when welding is applied, distortion can occur and produce additional costs of rework. Distortion became a potential problem in this process, since the joint undergoes significant thermal expansion and contraction, longitudinal and transverse shrinkages and leads to a non-desired welded structure. Recently, the usage of more lighted alloys in automobile sector ensures the conductor’s safety and reduction of emission; stainless steels have been placed in this industry as a compelling alternative for some carbon steels.