Performance and functionality are two key factors in designing advanced components. One promising approach in manufacturing design is the fabrication of multi-material structures by joining dissimilar materials. Steels, known for their outstanding properties and cost-effective production, are widely used across several industries. However, their high density presents challenges when designing lightweight components. A solution lies in combining steels with lightweight, non-ferrous alloys to develop cost-effective multi-material parts. However, joining different materials is generally complex due to their different properties, making it sometimes challenging or even unfeasible. Resistance element welding (REW) offers a high-performance alternative to traditional methods, such as resistance spot welding, with a high potential in mass production industries like automotive manufacturing. This article comprehensively reviews the latest research on REW for dissimilar joining of steels and non-ferrous alloys. It focuses on the microstructural and mechanical properties of joints, innovations in the REW process, the influence of process parameters on joint quality, as well as simulation and numerical studies. In addition, REW is compared with traditional joining methods.

This study investigates the friction stir welding (FSW) of a CuNiSiCr alloy produced by laser powder bed fusion and the role of post-weld heat treatments in the microstructural evolution and mechanical performance of welded joints. The as-built alloy exhibited columnar grains, porosity, and lack-of-fusion defects. FSW refined the microstructure within the stir zone (SZ) and dramatically reduced porosity, both in pore number and size, as revealed by X-ray tomography. Mechanical testing showed that FSW joints outperformed the as-built specimens, with increased yield and tensile strengths, albeit with reduced ductility. Aging at 500 °C markedly enhanced hardness across both the base material and the SZ, achieving peak values of about 195 HV after 2 h. Peak-aged joints reached yield and tensile strengths that were 17% and 16% higher, respectively, than those of the base alloy. Direct aging proved as effective as conventional solution treatment and aging, simplifying the heat treatment route. These findings show that FSW followed by direct aging offers a promising approach for obtaining high-performance joints, providing a viable pathway for producing large, complex, additively manufactured CuNiSiCr assemblies with improved structural integrity.

This study investigates butt friction stir welding of 4 mm thick A20X plates, which were produced using additive manufacturing through laser-powder bed fusion. The plates were joined at varying process parameters, including different welding and rotational speeds. Both the microstructure and the mechanical strength of the joints were examined, comparing joints in both as-printed and as-welded conditions.The joints welded at a welding speed of 100 mm/min and a rotational speed of 1500 rpm exhibited superior mechanical properties compared to those produced with other parameter settings. The results show that decreasing the rotational speed while increasing the welding speed leads to the formation of tunnel defects, compromising joint integrity and resulting in lower ultimate tensile strength. In contrast, the combination of 100 mm/min welding speed and 1500 rpm rotational speed produced defect-free joints, with an average ultimate tensile strength of 335 MPa and an elongation at fracture of 8.5%.

The newly introduced high manganese high strength (C + N) steel Printdur HSA was developed for the additive manufacturing process PBF‐LB/M. It consists of a fully austenitic grain structure. This study aims to evaluate the cyclic plastic material behavior of this (C + N) steel. Therefore, tensile tests and strain‐controlled low‐cycle fatigue tests were conducted. Strain amplitudes between 0.5% and 3.0% were applied. Furthermore, the microstructure was examined. In particular, electron backscatter diffraction and scanning transmission electron microscopy were applied. For all strain amplitudes, a general softening behavior is visible. The strain amplitude of 0.5% results in primary hardening within the first 30 cycles. Therefore, a dependency of the cyclic material behavior on the applied strain amplitude can be assumed. This behavior correlates with the investigated characteristics of the microstructure. The observed mechanical behavior is linked to microstructural mechanisms, including dislocation rearrangement, persistent slip band formation, and grain boundary interactions. A comparison with conventionally used PBF‐LB/M/316L highlights the superior static mechanical and fatigue performance of Printdur HSA. These results improve the understanding of the cyclic deformation mechanisms of this material and support its structural application under fatigue loading at high strains.

Laser powder bed fusion (LPBF) enables the production of high-strength A20X aluminum components with complex geometries for aerospace applications. However, the limited build volume of LPBF systems often requires separately manufactured parts to be joined. This study compares the microstructure and corrosion behavior of LPBF A20X under four material conditions: base material (BM), as-welded stir zone (SZ), solution-treated and peak-aged base material (BM–PA), and solution-treated and peak-aged stir zone (SZ–PA). Microstructural evolution was assessed using electron microscopy and X-ray diffraction, while corrosion behavior was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization in 3.5 wt.% NaCl solution. Among the tested specimens, BM exhibited the lowest corrosion current density (0.703 μA/cm²), followed by SZ (0.966 μA/cm²), BM–PA (2.257 μA/cm²), and SZ–PA (3.181 μA/cm²). The impedance response and post-polarization SEM observations indicated lower corrosion resistance after solution treatment and aging, particularly in SZ–PA. These findings are consistent with a possible contribution from micro-galvanic interactions involving redistributed and precipitated Cu-rich constituents, TiB₂ particles, and the Al matrix. Under the tested conditions, post-weld heat treatment reduced corrosion resistance compared to FSW alone. This underlines the need to optimize welding and heat-treatment parameters for LPBF A20X components.

CuNiSiCr alloy fabricated via laser powder bed fusion (LPBF) combines excellent thermal and electrical conductivity with good mechanical strength, making it well‐suited for advanced components in the energy and aerospace sectors. However, the limited build volume of LPBF systems constrains the size of the producible parts. Friction stir welding (FSW) enables the assembly of larger additively manufactured structures without the drawbacks of fusion‐based welding. Although FSW has been applied to LPBF aluminum and titanium alloys, its use in copper‐based systems remains unexplored. In this context, the effectiveness of FSW in joining LPBF CuNiSiCr alloy was investigated using welding speeds of 100 and 500 mm/min at a tool rotation speed of 900 rpm. FSW effectively eliminated porosity, refined the microstructure (2.8‐8 μm), and improved hardness (170 HV versus 84 HV in the as‐built alloy) within the welds through intense plastic deformation and recrystallization. XRD analysis showed a reduction in lattice strain and a {111} texture reorientation after welding. FSW improved mechanical strength, albeit at the expense of ductility: tensile strengths of 245 MPa at 100 mm/min and 235 MPa at 500 mm/min, with elongations at fracture of 7.3 and 7.9%, respectively (versus 216 MPa and 14.2% in the as‐built alloy). These enhancements, attributed to the combined effects of porosity reduction and grain refinement, demonstrate that FSW could be an effective method for assembling large‐scale LPBF CuNiSiCr components.