In this paper, laser welding Ni to Al using pulsed wave (PW) and continuous wave (CW) lasers was investigated. Weld quality and strength were evaluated in terms of cross-section examination, intermetallic compounds formation, microhardness, shear test and 90-degree peel test. The results show that deep penetration welding Ni to Al causes high melting pool temperature and severe material mixing, which could result in dominant AlNi₃ and AlNi intermetallics (IMCs) in the weld. These IMCs could significantly increase the hardness of the welding zone, but could also lead to the formation of defects, as well as reducing the ability to withstand the shear force and peel force applied to the weld. In comparison, using process optimization to maintain a shallow penetration or form a weld-braze joint, low melting pool temperature and minimum material mixing can be achieved. Hence, low-hardness Al₃Ni IMCs are prevalent in the weld. This helps generate a defect-free dissimilar weld joint to withstand higher shear force and peel force. The findings show promising applications, such as the battery management system of electric vehicles, in which joining a Ni adaptor to an Al bus bar is required.

This article designs a wall climbing robot for automatic welding of large steel member. In the past, welding of large member was generally carried out through manual welding or orbital semi-automatic welding, both of which have such disadvantages as low efficiency and poor flexibility. For these problems, this article proposes a wall climbing robot, primarily introduces its control system and planning of welding operation process. This robot can conduct Omni-directional movement on large member, and laser vision is adopted in the system for automatic tracking of seam. Based on the foregoing, a simulation and an automatic welding test is carried out, and the test result proves that this robot can complete automatic welding of large members.

Our previous work suggested that the Sn-3.8Ag-0.7Cu-xCe (x takes 0%, 0.2%, 0.5% and 1.0wt.%) solder melt experienced a temperature-induced liquid-liquid structure transition (L-LST) which was reversible during two heating and cooling cycles far above the liquidus. In this work, the effects of liquid state manipulations and rare earth element Ce addition on solidified Sn-3.8Ag-0.7Cu-xCe structures and properties were investigated. The results revealed that the microstructure was remarkably refined, the spread ability and the shear strength were enhanced when the melt experienced L-LST and Ce addition. Meanwhile, 0.2wt% Ce addition showed the most homogenous microstructure, leading to better properties. This work elicited that melt manipulations and Ce addition could be an effective way to optimize microstructure and properties of Sn-3.8Ag-0.7Cu-xCe soldered joints.

The detection of weld appearance defects of ship halls is mainly performed manually. Detection results depend on working experience, and working in ship halls is dangerous. In this paper, we design a crawling robot using the improved YOLOv5 to the detection of weld appearance defects on ship halls in real time. The features of weld appearance defects are not obvious and the detection objects are small. In addition, the attention mechanism is often used to enhance the features, and the small target detection layer can be used to strengthen small target recognition ability. Therefore, we improve YOLOv5 with CA and SPD-Conv to achieve good effect on detection of weld appearance defects. We apply the improved YOLOv5 model in the software of crawling robot, which makes the crawling robot detect the weld appearance defects on ship hulls in real time. The experimental results show that the improved model can effectively improve the mAP to increase by 0.026.

In this study, deposition of Tribaloy T800 on cobalt-based L605 substrate using micro-laser-aided additive manufacturing (micro-LAAM) was explored. The micro-LAAM process was studied to achieve sound integrity of the deposited layer. The microhardness and microstructure of the deposited Tribaloy T800 layer were investigated. The results showed that the developed micro-LAAM process can achieve single-layer crack-free deposition of Tribaloy T800 onto cobalt-based L605 without pre-heating of the substrate. Surface roughness of Ra 8 μm was obtained, indicating that micro-LAAM can significantly improve the surface quality. Very high microhardness in the range of 818 to 1000 Hv was achieved. Cellular grains with very fine dendritic microstructure and Laves phase were observed in the deposited Tribaloy T800, which contributed to the high hardness. With all the results obtained, it can be concluded that it is feasible to deposit Tribaloy T800 on L605 substrate with micro-LAAM to achieve sound integrity and high hardness.

The development of clean energy resources, including hydro power, plays an important role in protecting the global environment. Multi-layer bellows are key components and are widely used in hydro power plants. Due to the special multi-layer structures, conventional arc welding is prone to the defects of pores and insufficient fusion when fabricating or repairing such bellows. Precise laser welding with a high energy density and a low heat input has the potential to join multi-layer bellows in a high-quality manner. In this study, a comparative investigation was conducted on the arc welding and laser welding of multi-layer 316L stainless steel sheets and B610CF high-strength steel plates regarding the weld quality, microstructure and tensile properties. The results show that laser-welded joints produced a narrower heat-affected zone and a full weld without visible defects. Compared with arc welding, laser welding had more equiaxed grain regions in the fusion zone and a homogeneous elemental distribution in the heat-affected zone. This led to a more reliable welded joint using laser welding.