Laser joining of dissimilar metals, copper and aluminum, allows for the precise delivery of laser energy and high process speed. The keyhole-based process is very efficient for welding Al–Cu, considering the high reflectivity and thermal conductivity of the materials joined. For the Al–Cu system, the formation of detrimental intermetallic compounds is the main issue. Fusion welding with laser as a heat source involves the melting of metals. However, the high speed of the laser welding process is advantageous for terminating the excessive melting of Al and Cu and eventually controlling the detrimental intermetallic phases. Therefore, information pertaining to melted material is an important criterion for achieving joint strength. In this paper, the photodiode signal measured during the laser welding of Cu to Al is investigated as a process monitoring technique. In welding from Cu to Al, the melting of Al (bottom sheet) is very critical for joint strength. The amount of Al material that can be intermixed in Cu depends on the solubility limit of the Al–Cu system. The plasma plume emission during laser welding is used to extract the rapid melting of Al. This study shows the correlation of the Al characteristic peak at a wavelength of 396 nm with the shear strength of the joint.

中文翻译：

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铜与铝激光熔焊过程中的光信号相关性

异种金属（铜和铝）的激光接合可实现激光能量的精确传递和高加工速度。考虑到所连接材料的高反射率和热导率，基于键孔的工艺对于焊接铝-铜非常有效。对于Al-Cu系统，有害的金属间化合物的形成是主要问题。以激光为热源的熔焊涉及金属的熔化。然而，激光焊接工艺的高速对于终止Al和Cu的过度熔化并最终控制有害的金属间相是有利的。因此，有关熔融材料的信息是获得接头强度的重要标准。在本文中，作为过程监测技术，研究了将铜激光焊接到铝时测量的光电二极管信号。在从Cu到Al的焊接中，Al（底部薄板）的熔化对于接头强度非常关键。可以在Cu中混合的Al材料的数量取决于Al–Cu系统的溶解度极限。激光焊接过程中的等离子羽流发射用于提取Al的快速熔化。这项研究表明，在396 nm波长处的Al特征峰与接头的剪切强度相关。