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In this work, three cooling strategies were proposed to increase the cooling rate and avoid extensive exposure to higher temperatures during the manufacturing of components in Inconel 625 using wire arc additive manufacturing (WAAM): forced cooling with compressed dry air jet, interpass idle time and the combination of both strategies. These strategies were compared for two welding technologies within gas metal arc welding (GMAW) process: pulsed and cold metal transfer (CMT). The results show that deposition using the GMAW-CMT welding mode showed better quality and uniformity than the GMAW-pulsed mode. The tested interpass idle time did not cause a significant effect on the mechanical properties, while the forced cooling using an air jet slightly improved the properties and may be used to increase productivity, especially for larger components. [ABSTRACT FROM AUTHOR]

Aluminum has become increasingly important in the automotive sector due to its ability to reduce vehicle weight without compromising structural performance. However, joining different types of aluminum alloys can be challenging due to their different thermal and mechanical characteristics. Concurrently, friction stir processing (FSP) is a material processing technique that has garnered considerable attention for its versatility and industrial applicability, and it may represent a preliminary phase to correctly perform friction stir welding, which is a welding technology used to join different types of aluminum alloys. In this context, this study presents an extensive experimental campaign of FSP performed on 5754-H111 and 6082-T6 alloys, varying two rolling directions and four welding speeds. The processed materials were characterized, including cupping and tensile tests, microstructure analysis, and a correlation between welding parameters, microstructure, and mechanical resistance. In addition, a numerical method was proposed to simulate the Erichsen tests and predict the formability of the materials, before and after the FSP processes. The results showed that both alloys exhibited good formability after the FSP process, but with different behavior. AA6082 underwent internal decohesion and dynamic recrystallization, resulting in the absence of defects and an increase in ductility and cold formability. AA5754 experiences more difficulty with material flow during FSP and showed the presence of tunnel defects in all analyzed process conditions. However, the alloy 5754 did not undergo softening and had comparable mechanical behavior and cold formability to the base material. These results were validated by the numerical method proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the dissimilar friction stir lap welding of AA2198 and AA7075 sheets. The influence of processing parameters, namely welding speed and tool rotational speed on joint features, microstructure, and mechanical properties were studied by implementing a full factorial design of experiments. Axial and transversal forces were continuously measured during the welding process using a sensed fixture aiming at the correlation of processing parameters, forces, and quality of the achieved joints. Obtained outcomes showed hook formation for all the combination of parameters and the existence of a very narrow processing window in which it is possible to avoid the formation of internal defects, such as grooves and tunnels. The influence of the weld bead morphology on the lap shear strength was elucidated proving that the strength is ruled by the hook morphology. The microstructure of the joints was studied and discussed considering also the microhardness distribution. [ABSTRACT FROM AUTHOR]

Niobium is a material widely used for particle accelerating facilities, such as cavities. These components are usually obtained through forming processes, and then to understand the friction behavior of niobium sheets during the forming process can be very useful. Therefore, in this work the friction behavior of niobium sheets under conditions similar to the ones faced in forming processes has been studied. Pin-on-disk tests have been carried out in both dry and lubricated conditions, and different values of contact force in the range of 2.5 and 20 N have been adopted to observe and understand the tribological behavior of niobium. The worn surfaces have been observed through a scanning electron microscope and EDX analyses to reveal the wear mechanisms. The experimental outcomes proved that niobium exhibits very high friction coefficient with a severe adhesive wear under dry condition, while a lower friction coefficient with a less severe wear mechanism has been observed when lubricant is adopted. [ABSTRACT FROM AUTHOR]