It is expected that the application of aluminum alloy, a lightweight material, will continue to increase in connection with strengthening international environmental regulations and improving fuel efficiency for reducing vehicle emissions. Accordingly, aluminum alloys are widely applied to the automobile industry, and various welding methods are used for aluminum alloys. In this paper, the laser-arc hybrid welding method that combines laser and arc welding is explained. Although laser-arc hybrid welding has better weldability than a single heat source of laser or arc, the degradation of mechanical properties due to defects occurring during hybrid welding has emerged as a problem. This paper discussed the quality of aluminum alloy welds through optimization of various process parameters of hybrid welding.

This study observed the effect of filler metal type on mechanical properties of NAB (NiAl-bronze) material fabricated using wire arc additive manufacturing (WAAM) technology. The selection of filler metal type is must consider the field condition, mechanical properties required by customers, and economics. This study analyzed the bead shape for representative two kind of filler metal types use to maintenance and fabricated a two-dimensional bulk NAB material. The cold metal transfer (CMT) mode of gas metal arc welding (GMAW) was used. For a comparison of mechanical properties, the study obtained three specimens per welding direction from the fabricated bulk NAB material. In the tensile test, the NAB material deposited using filler metal wire A showed higher tensile strength and lower elongation (approx. +71 MPa yield strength, +107.1 MPa ultimate tensile strength, −12.4% elongation) than that deposited with filler metal wire B. The reason is that, a mixture of tangled fine α platelets and dense lamellar eutectoid α + κ_III structure with β′ phases was observed in the wall made with filler metal wire A. On the other hand, the wall made with filler metal wire B was dominated by coarse α phases and lamellar eutectoid α + κ_III structure in between.

Aluminum exhibits excellent workability and formability due to its crystallographic properties and has outstanding specific strength, making it widely used in various industries. In particular, it is widely applied in the automotive industry, and various welding methods are being used to advance joining technology. Among these methods, hybrid welding, which combines laser and arc welding, has been extensively researched to overcome the limitations of both conventional laser welding and arc welding, resulting in high-quality welds. However, there is a lack of studies comparing the welding characteristics when using wires from conventional Gas Metal Arc Welding (GMAW) in laser-arc hybrid welding, specifically in relation to the wire diameter. This study analyzed the mechanical properties and microstructure based on different wire diameters. The sample with a wire diameter of 1.2 mm exhibited a finer equiaxed grain structure compared to the sample with a diameter of 1.6 mm, and it also showed a lower porosity. As a result, the mechanical strength of the sample with a wire diameter of 1.2 mm was found to be higher.

In this study, the melt pool formation behavior of high-speed laser-arc hybrid welding of aluminum plates was simulated using finite element analysis (FEA). To evaluate the heat input efficiencies of the laser and arc, standalone laser or arc welding experiments were conducted using the same arc or laser processing parameters as those employed in hybrid welding. These experiments were also simulated using FEA to calibrate the laser and arc heat adsorption parameters. The melt pool shapes were measured from cross-sectional optical microscope (OM) images of the specimens and subsequently used to develop a thermal analysis simulation of the laser and arc welding processes. A simulation model for the laser-arc hybrid welding process was developed by combining the heat input models of the laser and arc welding processes. The FEA model successfully predicted the melt pool shapes observed in the experiments. The accuracy of the developed model was evaluated, yielding average errors in the melt pool sizes of the laser, arc, and hybrid welds of 5.43%, 6.89%, and 4.51%, respectively.

This study entailed resistance spot welding conducted using 1.8 GPa-grade hot stamping boron steel heat-treated under varied conditions. The relationship between weldability and melting behavior of the intermetallic layer during resistance spot welding was examined. As regards the four heat treatment conditions beyond the austenitic temperature, it was found that the intermetallic layer thickened with increased time and temperature. Furthermore, the contact resistance also increased with increased time and temperature of the heat treatment. This was mainly because of the expansion of the area of Al-Fe-based intermetallic phases (e.g., FeAl2 and Fe2Al5) within the intermetallic layer. Contact resistance induces the thickening of the intermetallic layer and results, even with a low current, in the occurrence of expulsion due to the high heat generation in the faying surface. Subsequently, the weldable current range became narrow, and satisfying the property requirements was challenging. The welding using the heat treatment condition of 900 °C and 5 min showed sufficient current path area. This can be attributed to the phenomenon that the intermetallic layer was forced out to the rim of the corona bond area at an early stage of the welding. However, the welding using other conditions showed that the intermetallic layer remained on the border of the nugget and corona bond areas it was observed and verified via electron probe micro analysis. Consequently, the nugget was insufficiently formed and the fracture mode was a partial interfacial fracture. On the contrary, it was found that the adoption of the pre-pulse could enhance the weldability of all conditions by obtaining a larger contact area.

This study investigated deposition parameters for ER70S-6 solid wire deposited using the Wire Arc Additive Manufacturing process. In addition, the microstructure and mechanical properties of deposits fabricated using optimized deposition parameters were compared and analyzed. As the wire feed rate increased, the width and height of the beads tended to increase together. The analysis of effective rectangle area revealed the highest value when the inter-pass overlap was set to 72 % for the first layer and 68 % for subsequent layers. Additionally, the ratio of effective rectangle area tended to in1crease with longer inter-layer dwell times. As a result of the microstructural analysis, the fusion zone exhibited fine grains regardless of the deposited height, but the heat-affected zone was relatively narrow and fine grained as the deposited height increased. It is expected that the bottom heat-affected zone is relatively non-uniform and forms a large microstructure compared to the top due to the repeated thermal cycles occurring in the WAAM process and the heat accumulation occurring in the previous layer. Tensile tests in horizontal and vertical directions showed that the yield strength and ultimate tensile strength were similar, but the elongation was relatively higher in the horizontal direction than in the vertical direction due to the anisotropy of the microstructure that is mainly observed in additive manufacturing.