The present study aimed to enhance the efficiency and efficacy of the Al/Cu joint production process implemented by the company VEMID Ltd., Jagodina, Serbia, by attaining sound joints within a very short welding time. For this purpose, the present study aimed at investigating the accuracy and the quality of the continuous drive friction welding (CDFW) process, as well as the optimum combination of CDFW parameters with highest joint efficiency in terms of investigated properties. The accuracy was estimated through an analysis of temperature–time curves recorded during CDFW using an infrared camera. The quality was evaluated through an investigation of the properties of Al/Cu joints produced using different friction (66.7, 88.9, and 133.3 MPa) and forging (88.9, 222.2, and 355.6 MPa) pressures and a constant total welding time (4 s) and rotational speed (2100 rpm). Thermal imaging with an infrared camera demonstrated that the actual total welding time was 15% longer compared to the nominal value. This was attributed to the slow pressure response of the pneumatic brake system. The relative changes in the maximum surface temperature (T_MS) during the CDFW process corresponded to changes in welding pressures, indicating the potential of the thermal imaging method for monitoring and assessing this process. A preliminary investigation demonstrated that Al/Cu joints produced using welding pressures less than 88.9 MPa often displayed the presence of non-joined micro-regions at the Al/Cu interface and a significant thickness of interfacial Al₂Cu (up to 1 µm). However, when friction pressure was set at 66.7 MPa, an increase in the forging pressure to 222.2 MPa eliminated the presence of non-joined micro-regions and reduced the thickness of Al₂Cu to 0.5 µm on the average level. These Al/Cu joints achieved the highest joint efficiencies in terms of strength (100%) and ductility (61%). They exhibited an electrical conductivity higher than 92% of the theoretical value. A further increase in any welding pressure produced similar or deteriorated properties, accompanied by an increase in the consumption of raw materials and energy. Such turn of events was counterproductive to the original goal of increasing the efficiency and efficacy of the CDFW process.

Despite the surge in plasma nitriding research, few reviews thoroughly examine how surface decarburization—occurring both before and during the treatment—affects AISI 4140 and similar steel grades. This review addresses that shortfall by providing an investigation into the decarburization process and its consequences. It compiles essential findings from prior studies, demonstrating instances of decarburization in both plasma-free and plasma-containing environments. Furthermore, this analysis explores strategies to prevent decarburization and assesses its significant impact on the steel’s microstructure, hardness, corrosion resistance, and wear properties in surface and near-surface regions. Moreover, this study proposes directions for future research, emphasizing the necessity for a more detailed understanding of the decarburization mechanisms and their influence on the properties of plasma-nitrided steels.

The present study examined the effect of heat input and T6 post-weld heat treatment on the microstructure, electrical conductivity, and intergranular corrosion of AA6026/AA5183/AA6026 welded joints. The samples were welded using pulsed MIG, pulsed TIG, and combined TIG&MIG procedures, and a portion of samples was subjected to the T6 condition (solution annealing, water quenching, and artificial aging). The results showed that lower heat input (pulsed MIG) reduced intermetallic precipitation along grain boundaries and thereby improved resistance to intergranular corrosion, while higher heat input (pulsed TIG) promoted more intensive precipitation and increased the risk of corrosion. The T6 treatment partially homogenized the microstructure but also likely promoted the precipitation of Mg₂Si along grain boundaries in the heat-affected zone of AA6026 and the formation of continuous β-Al₃Mg₂ films along grain boundaries in the weld metal of AA5183, which together increased susceptibility to intergranular corrosion of welded joints. The best resistance to intergranular corrosion was observed in joints produced by pulsed MIG welding with low heat input, while TIG&MIG joints, owing to even lower heat input, maintained stable intergranular corrosion resistance even after T6 treatment. In contrast, joints obtained by pulsed TIG welding with higher heat input suffered the most severe degradation of intergranular corrosion resistance in the T6 condition. These findings confirmed that heat input control was the decisive factor governing microstructural changes, electrical conductivity, and corrosion behavior of AA6026/ER5183/AA6026 welded joints.