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This study aims to investigate a friction stir welded joint between steel and aluminum alloy. FSW is nowadays one of the most interesting joining techniques due to the possibility of connecting materials and thicknesses that are difficult or impossible to weld with traditional techniques. The main advantage is that materials are not affected by thermal cycle problems during solidification and cooling, and the absence of fumes and pollution during the process favors the quality of the welded joint. The life of metal joints could be greatly reduced in a corrosive environment since the less noble material will tend to increase its corrosion rate, while the nobler one will reduce its electrochemical dissolution. Accelerated aging tests (i.e., salt fog test) are used to estimate the lifetime of metal joints in highly aggressive environments. The aim of the present work is to evaluate the durability at a long aging time in the salt spray test (according to ASTM B117) of carbon steel/aluminum alloy joints, obtained by FSW. In this first part, mechanical test results are reported. A deep metallographic and chemical investigation is going to be reported in part two. The current research work investigates the welding direction and residence time in the salt spray chamber. The breakage of all tested samples, evaluated after the tensile tests were carried out, always occurs at the interface of the joint, regardless of the change of direction of the weld on the advancing or retreating side. The welding direction influences the breakage of the joint only before the aging treatment. Specifically, specimens produced in advance are characterized by increased joint strength. On the other hand, the factor that influences the performance of the joints is the exposure time where, starting from the first point of aging, i.e., after two months, there is a decrease in the maximum load of 40%, and the effect of corrosion leads to a significant deterioration of the weld which remains almost similar until the last point of aging.

Friction Stir Welding is a suitable solid-state joining technology to connect dissimilar materials. To produce an effective joint, a phase of optimization is required which leads to the definition of process parameters such as pin geometry, tool rotational speed, rotation direction, welding speed, thickness of the sheets or tool tilt angle. The aim of this review is to present a complete and detailed frame of the main process parameters and their effect on the final performance of a friction stir welded joint in terms of mechanical properties and microstructure. Attention was focused in particular on the connection between different aluminum alloys. Moreover, the experimental results were correlated to the development and the applications of tools which can be effectively used in the design of the manufacturing process such as finite element analyses, artificial neural networks, and statistical studies. The review also aims to be a point of reference to identify the best combinations of process parameters based on the dissimilar aluminum to be joined.

In an innovative vision of manufacturing, orbital riveting is a joining technique characterized by high efficiency, energy saving, low costs and low noise. It is a cold forming process where a tool rotates at a fixed angle (i.e., typically 3° to 6°) to create a sweeping line of pressure around a rivet. This movement progressively promotes, with each rotation, the collapse of the rivet shank down onto the upper substrate of a joint, permanently forming a rivet head. The aim of this research is to make and test multi-material joints between an aluminum AA5083 H111 sheet and a glass fiber reinforced laminate. Specifically, nine configurations of single lap joints were studied by investigating the effect of the thickness (i.e., 2.5, 3.0 and 4.0 mm for the aluminum and 2.5, 3.0 and 4.0 mm for the composite laminate) both on the mechanical characteristics and on the failure modes.

In the industrial field, manufacturing time is one of the most important factors affecting production costs. Structural adhesives require long curing times (i.e., 3–4 weeks) before the joined components can be safely employed. The aim of the present work is to test the effect of several thermal treatments on a commercial epoxy structural adhesive on the final resistance of single lap joints, trying to attain the possibility of a curing time reduction. Aluminum alloy 5083, typically employed in marine applications, is used as the substrate. Both the adhesive and the joints are treated at different temperatures/times, and then tensile tests are carried out to obtain the mechanical resistance and study the failure modes. A statistical analysis allows the evaluation of the effects of the thermal cycles on the mechanical performances of the joints and the comparison with those cured with the standard procedure.