Laser welding of copper to aluminum with spiral trajectory and identification of excessive aluminum melting

in Journal of Laser Applications (2022)

Laser welding of copper and aluminum is challenging due to the formation of complex intermetallic phases. Only a defined amount of Al and Cu can be melted because of the limited solubility of Al–Cu ... [more ▼]

Laser welding of copper and aluminum is challenging due to the formation of complex intermetallic phases. Only a defined amount of Al and Cu can be melted because of the limited solubility of Al–Cu systems. Finding the optimum melting is critical for a strong joint. Optical emission during the welding process contains the metal vapor of Al metal that is being welded. This is a good indicator for monitoring the welding process. This research paper focuses on the optical emission of Al from the bottom sheet during welding of Cu (top) and Al (bottom) in overlapped configuration for a spiral trajectory. The emitted signal in the range of 395 nm (±3 nm) from the bottom sheet of aluminum is used to identify excessive Cu–Al welding. The tensile shear strength, microstructure, and welding signal in the time domain for optimum and excessive weld conditions are investigated. In this study, a technique using a photodiode is shown to identify the excessive melting of Al during the welding process in real time. [less ▲]

Correlation of Optical Signal During Laser Fusion Welding of Copper to Aluminum

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 ▲]

WELDING COPPER TO ALUMINIUM WITH GREEN LASER WAVELENGTH OF 515 NM

Scientific Conference (2020, October 19)

Joining copper and aluminum sheets is difficult because of brittle intermetallic phases (IMP) formed in the joint, which results in reduced performance. The traditional approach to overcome this issue is ... [more ▼]

Joining copper and aluminum sheets is difficult because of brittle intermetallic phases (IMP) formed in the joint, which results in reduced performance. The traditional approach to overcome this issue is to irradiate the laser beam from Aluminum (Al) to control the weld depth and mixing of Cu in Al. The laser welding approach from the copper side (Cu on top) to Al is very sparse in the literature. In this paper, the welding approach from copper (top sheet) to aluminum is studied with green laser (515 nm) due to improved absorption at this wavelength. The objective of irradiating the laser beam from the copper side (Cu on top) is to exploit the higher solubility of Al in Cu (about 18%), which is significantly higher than Cu in Al. Therefore more Cu and Al can be melted and mixed in the joint for copper sheet placed on the top. From the tensile shear test, a strong joint is obtained with a fracture on the heat-affected zone (HAZ) of Al. Detailed microstructure and composition of Al and Cu in the joint is performed by Energy-dispersive X-ray spectroscopy (EDS) to investigate the composition in the joint. The EDS analysis indicates that a large amount of beneficial Cu solid solution and Al-rich phases is formed in the joint. The detrimental phases are intermixed in between the ductile phase composition i.e Al-rich and Cu solid solution. Therefore the effect of detrimental intermetallic phases is mitigated by intermixing with large ductile phases. With this paper, the fusion welding approach for joining Cu and Al system with a significant level of Cu and Al melting is shown. [less ▲]

Laser beam joining of copper to aluminum sheet

Poster (2019, April 04)

Dissimilar metal joining plays a very important role in the battery connections, especially copper and aluminum sheets. The existing literatures for laser research mostly focused on joining from the less ... [more ▼]

Dissimilar metal joining plays a very important role in the battery connections, especially copper and aluminum sheets. The existing literatures for laser research mostly focused on joining from the less reflective aluminum side to bond with copper. In the current research, we explore the joining process from copper side.Finally the optical emission of Cu-Al joint is presented with 394 nm peak as an indication to study the melting of Al. [less ▲]

Metallographic Studies of Dissimilar Al-Cu Laser-Welded Joints Using Various Etchants

in Metallography, Microstructure, and Analysis (2018)

The welding of Al and Cu is considered as difficult due to the formation of intermetallic compounds, which cause a brittle joint with increased electrical resistance. This paper investigates etching ... [more ▼]

The welding of Al and Cu is considered as difficult due to the formation of intermetallic compounds, which cause a brittle joint with increased electrical resistance. This paper investigates etching techniques that were used to contrast the intermetallic compounds for optical microscope analysis. A 0.5 mm AA-1050 sheet was welded to a 0.5 mm SF-Cu sheet in overlap configuration. The cross sections were etched by using 17 different reagents, including common Al-grade 2xxx etchants, Al-bronze etchants, and specific IMC etchants. A complete microstructural characterization, including the formation of intermetallic compounds, is presented. The experimental result showed that a clear distinction of metallurgic structures is possible, thus enabling a more detailed analysis of Al-Cu welds. It was found that etchants #09, #14, and #16 revealed best the four different intermetallic compounds θ-Al2Cu, η-AlCu, ζ-Al3Cu4, and γ-Al4Cu9. [less ▲]