Low power pulsed laser-MAG hybrid welding was carried out by different heat source arrangement methods (lead mode, distance between laser spot and welding wire tip (DLA)). The coupling effect and welding characteristics of hybrid heat sources under different modes were studied by using high speed image (HSI) and real-time electrical signals. HSI observation and electronic signals showed that the lead mode and DLA significantly affect the coupling state of heat source and welding characteristics (weld morphology, process stability and droplet transfer). The influence of lead mode on weld forming was more significant than that of DLA.In laser-lead mode, when DLA = 1~2mm, the laser and arc had perfect coupling effect, good weld formation, less spatter and greater penetration. In arc-lead mode, the weld formation was poor and undercut defects were common, while the overall penetration was greater than that in laser-lead mode. In terms of welding process stability, arc-lead mode was better than laser-lead mode. The pulsed laser increased the stability of projected transition, produced more fine droplets and reduced the generation of spatter. When DLA = 1~2mm, stable droplet transfer could be realized under both modes.

Low power pulsed laser-MAG hybrid welding was carried out by different heat source arrangement methods (lead mode, distance between laser spot and welding wire tip (DLA)). The coupling effect and welding characteristics of hybrid heat sources under different modes were studied by using high speed image (HSI) and real-time electrical signals. HSI observation and electronic signals showed that the lead mode and DLA significantly affect the coupling state of heat source and welding characteristics (weld morphology, process stability and droplet transfer). The influence of lead mode on weld forming was more significant than that of DLA. In laser-lead mode, when DLA = 1~2mm, the laser and arc had perfect coupling effect, good weld formation, less spatter and greater penetration. In arc-lead mode, the weld formation was poor and undercut defects were common, while the overall penetration was greater than that in laser-lead mode. In terms of welding process stability, arc-lead mode was better than laser-lead mode. The pulsed laser increased the stability of projected transition, produced more fine droplets and reduced the generation of spatter. When DLA = 1~2mm, stable droplet transfer could be realized under both modes.

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In this paper, the effect of different surface pretreatment method on properties of vacuum brazed joint of AlSi50 alloy was investigated. The surface pretreatment methods of specimen before brazing include sanding, NaOH corrosion, HCl corrosion, H2SO4 corrosion and nickel plating. The experimental results indicate that the width of brazing joint varies with different surface pretreatment methods. The joint with sanding pretreatment, has the largest brazing seam width of 20 μm. Meanwhile, joint with H2SO4 corrosion has the narrowest brazing seam width. The brazing filler metal can wet and spread on different pretreated specimen very well. Spectrum analysis indicates that nickel-plate on AlSi50 surface, can interact with brazing filler metal, which increases mechanical property of brazing joint. For brazing of AlSi50 alloy, the optimal pretreatment method is nickel plating. After nickel plating pretreatment, brazing joint has the maximum shear strength 82.05 MPa by using brazing filler metal Al52-Cu33-Mg12-Ni3 and following technological parameters: brazing temperature 580 ℃, soaking time 30 min and pressure 3 MPa.