Laser welding is one of the most promising joining techniques to realize hybrid joints between metals and polymers in order to achieve weight reduction and functionalization of the parts. The surface treatment of the metal has a decisive effect on the joint quality and thus on the mechanical properties. In the present study, different mechanical and laser-based surface treatments have been investigated to develop diverse surface conditions on aluminum. Abrasive blasting and laser ablation were used to increase the surface roughness, while abrasive polishing and laser polishing were applied to minimize the surface roughness. In contrast to abrasive surface treatments, laser-based ones were implemented to create artificial oxide layers on the aluminum surface. The surface structures of pretreated samples have been studied with scanning electron microscopy and roughness test. The laser welding of pretreated aluminum with polyamide was achieved with the heat conduction joining technique. To enlarge the welding area and control the heat input, spatial and temporal modulations of the laser beam were implemented. Finally, a single lap tensile-shear test, microscopic analysis of fractured surfaces, and welding cross sections were employed to evaluate the joints. Results show that the presence of an artificial aluminum oxide layer and low roughness are essential to achieve a superior joint between aluminum and polyamide (improvement of approximately 58% in the shear load of the joint compared to as-received welded samples). The cross section of the superior joint which is the laser-polished aluminum welded to polyamide is studied with transmission electron microscopy.

中文翻译：

---

基于不同表面条件的铝-聚酰胺激光焊接接头评估

激光焊接是实现金属和聚合物之间混合连接以实现零件重量减轻和功能化的最有前途的连接技术之一。金属的表面处理对接头质量具有决定性的影响，因此对机械性能也具有决定性的影响。在本研究中，已经研究了不同的基于机械和激光的表面处理，以在铝上开发出多种表面条件。使用喷砂和激光烧蚀来增加表面粗糙度，而使用磨料抛光和激光抛光来使表面粗糙度最小。与磨料表面处理相反，基于激光的处理在铝表面上创建了人造氧化物层。预处理样品的表面结构已通过扫描电子显微镜和粗糙度测试进行了研究。预处理铝与聚酰胺的激光焊接是通过热传导连接技术实现的。为了扩大焊接面积并控制热量输入，对激光束进行了时空调制。最后，采用单圈拉伸剪切试验，断裂表面的微观分析和焊接横截面来评估接头。结果表明，人造氧化铝层的存在和低粗糙度对于在铝和聚酰胺之间实现卓越的接合至关重要（与按原样焊接的样品相比，接合处的剪切载荷提高了约58％）。