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See detailCorrelation of Optical Signal During Laser Fusion Welding of Copper to Aluminum
Mathivanan, Karthik UL; Plapper, Peter UL

in Journal of Laser Applications (2021, January 05), 33(1),

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 ... [more ▼]

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. [less ▲]

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See detailEVALUATION OF THE JOINT BASED ON DIFFERENT SURFACE CONDITIONS FOR ALUMINUM-POLYAMIDE LASER WELDING
Amne Elahi, Mahdi UL; Koch, Marcus; Plapper, Peter UL

in Journal of Laser Applications (2021)

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 ... [more ▼]

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. [less ▲]

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