铝合金对近红外光纤激光反射率高，激光能量利用率低，目前通常采用“万瓦级”光纤激光实现铝合金的高速激光焊接. 文中采用激光压力焊接的方法，实现了铝合金“千瓦级”光纤激光的高速焊接. 研究了不同工艺参数下焊缝的成形性，计算了激光能量的汇聚规律，并利用电子背散射衍射技术(EBSD)对焊缝微观结构进行表征. 结果表明，激光功率为1～6 kW、焊接速度为5～20 m/min时均可实现焊接. 当激光功率为6 kW时，焊接速度可达50 m/min. 计算结果证明，激光压力焊接方法具有显著的能量汇聚作用，功率密度最大可达到原始聚焦激光束的4.6倍，提高了激光能量的利用率. 通过对焊缝微观组织的表征进一步证明，激光能量汇聚作用实现了材料的快速熔化凝固，随后在压力作用下，填充了搭接间隙.
At present, a commercial fiber laser welding of aluminum alloy at high welding speed is achieved at tens of kilowatts power level due to extremely high reflectivity of aluminum alloy at the near-infrared wavelength. In this work, high-speed welding of aluminum alloy was realized by using low-power (kilowatts power level) fiber laser combined with pressure. The influence of process parameters on the weld formation, the variation of energy convergence during laser pressure welding, and the microstructure characterization by using electron backscatter diffraction (EBSD) were investigated through both simulation and experiments. The results show that successful welding was achieved at laser power from 1 kW to 6 kW and welding speed from 5 m/min to 20 m/min. It is worth noting that successful welding was achieved even at 50 m/min when laser power was 6 kW. Simulation showed that laser pressure welding provided significant energy convergence, which resulted in the power density up to 4.6 times higher than the original focused laser beam, indicating an efficient usage of laser energy. Microstructure of the welds further proved that laser energy convergence led to rapid melting and solidification of the material, which subsequently eliminated the lap gap under pressure.
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