To clarify the effect of the laser-induced plume on weld penetration during high-power fiber laser welding, this paper investigates the change in weld penetration, plume behavior and temperature, particles present in the plume, and the attenuation of the horizontal probe laser. Results show that the weld penetration had an improvement of about 20% as the plume was blown away by using a supersonic cross jet. The plume temperature at a height of 5 mm was approximately 5078 K. The weld penetration, plume temperature, and plume attenuation to a probe laser decreased as plume height increased. A plume height of approximately 80 mm resulted in a shape similar to that of a focused laser beam; a cone of white smoke composed of numerous particles appeared around the plume. Calculated and measured results indicate that the interaction of laser particles in the plume accounts for the primary impact on laser-plume interaction. It is found that, if the plume height increases, the weld penetration decreases correspondingly due to the increasing attenuation of the high-power fiber laser beam by the particles in the plume.

The keyhole wall is the interaction interface between the laser and the material during the laser deep penetration welding. Measuring the morphology of the keyhole wall is thus of significance for understanding the high power fibre laser deep penetration welding process. In this paper, the clear keyhole wall was reserved by suddenly closing laser during high power fibre laser welding of copper alloy. The results indicate that the keyhole can be divided into laser action region and metallic vapour pressure maintenance region. The laser action region is on the front wall of keyhole, and a series of concentric elliptical rings are observed in this region. In another region, its diameter is significantly larger than the spot diameter and the keyhole wall is basically smooth. The results are different from those generally accepted viewpoints, which clarify the flowing law of molten fluid in the keyhole and are thus of great guiding significance for optimising the welding technology.

In this work, laser pressure welding of dissimilar aluminium and copper was conducted at a high welding speed of 15 m min⁻¹. One-micron intermetallic compounds (IMCs) layer with heterogeneous dual-phases (copper and γ-Al₄Cu₉ phases) laminates in the joint interface were observed by transmission electron microscopy. The results showed that the combination of two joining mechanisms led to improved mechanical property, namely the mechanical interlocking due to the curved interface and the metallurgical bonding by the presence of the thin IMCs layer with heterogeneous laminates. The tensile shear force and the shear strength of the joint reached 2055 N and 111.94 MPa, respectively. The present study provides a more efficient method to join dissimilar aluminium and copper.

Coral-like porous Si was fabricated through the dealloying of a laser remelted as-cast AlSi12 alloy(Al-12 wt % Si). The porous Si was composed of interconnected micro-sized Si dendrites and micro/nanopores, and compared to flaky Si, which is fabricated by direct dealloying of the as-cast AlSi12 alloy. The structure of the porous Si was attributed to the dendritic solidification microstructure formed during the laser remelting process. The micropore size of the porous Si decreased from 4.2 μm to 1.6 µm with the increase in laser scanning velocity, indicating that the morphology of porous Si could be easily altered by simply controlling the laser remelting parameters. The coral-like porous Si provided enough space, making it promising for high-performance Si-based composite anode materials in lithium-ion batteries. The proposed hybrid method provides a straightforward way of tuning the porous structure in the dealloyed material.