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Copper is well-known for excellent conductivity and corrosion resistance, whereas aluminium is known for low density and great formability. The laser joining of Al and Cu combines those properties, e.g. in manufacturing of solar absorbers and wiring harnesses. Furthermore, the joining of Al and Cu is an enabler of new products, e.g. the manufacturing of battery modules, where a reliable joining process for numerous Al-Cu connections, the tabs of the Li-ion batteries, is needed. The joining of Al and Cu is considered as complex due to the formation of intermetallic compounds inside the joint, which are causing a brittle joint with increased resistance. The focus of this work is the improvement and extension of the laser welding process of Al and Cu. It was found that the determination of suitable process parameters is one of the major restrictions in the application of the process. Hence, this work deals with the analysis of methods to determine process parameters, which was performed in three main parts: o The comprehensive process understanding is one essential part to improve the joint quality. The formation of the intermetallics inside the joint is a process, which takes place in a short time frame of a few μs and a scale of few hundreds of μm. Metallographic studies were performed to gain insights into the local formation of specific intermetallic compounds. Furthermore, intensive research on etchants was combined with the information gained from a micro-XRD analysis in order to identify and localize the most critical phases. o The post–process quality measurements are the essential part to quantify and evaluate the properties of the joint and thus to adapt process parameters. Yet, the quality measurements are varying in recent literature. In this work, the mechanical, electrical and optical methods were combined with hardness measurements and metallographic studies. The methods were enhanced and it was found that especially electrical methods have a great poten

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.

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.

This paper describes a novel method to analyze the effect of the fiber laser induced plasma on welding of dissimilar Al and Cu. Based on spectroscopic studies, specific wavelengths were found to be suitable for process monitoring during laser welding. For aluminum, the double peak at 394.4 and 396.1 nm was studied, for cu the 578 nm peak was studied. The characteristic peaks were observed by multiple photodiodes equipped with narrow optical filters with varying FWHM. Analyzing the plasma emissions of the process enabled to detect material changes in the plasma plume. This novel method has the advantage of higher sampling rate combined with reduced costs compared to a spectrometer and is thus able to capture the process dynamics.

This paper presents the characterization of the intermetallic phases of laser-welded Al-Cu joints by synchrotron trough-the-substrate microdiffraction combined with SEM/EDX and etched/non-etched optical micrographs. Transmission microdiffraction offers the spatial resolution and beam flux necessary to study the intermetallic phases, which in conjunction with the excellent contrast of etched micrographs, rendered possible the phase identification. It was found that the major phases are Al2Cu (θ), Al4Cu9 (γ1) and AlCu (η2) were formed. The Al3Cu4 (ζ1) and δ phases where formed in less amount and found to be the primary cause for cracks inside the weld seam and therefore for the failure of the joint.

This paper presents the characterization of the intermetallic phases of laser-welded Al-Cu joints by synchrotron trough-the-substrate microdiffraction combined with SEM/EDX and etched/non-etched optical micrographs. Transmission microdiffraction offers the spatial resolution and beam flux necessary to study the intermetallic phases, which in conjunction with the excellent contrast of etched micrographs, rendered possible the phase identification. It was found that the major phases are Al2Cu (θ), Al4Cu9 (γ1) and AlCu (η2) were formed. The Al3Cu4 (ζ1) and δ phases where formed in less amount and found to be the primary cause for cracks inside the weld seam and therefore for the failure of the joint.

This paper describes a novel method to analyze the effect of the fiber laser induced plasma on welding of dissimilar Al and Cu. Based on spectroscopic studies, specific wavelengths were found to be suitable for process monitoring during laser welding. For aluminum, the double peak at 394.4 and 396.1 nm was studied, for cu the 578 nm peak was studied. The characteristic peaks were observed by multiple photodiodes equipped with narrow optical filters with varying FWHM. Analyzing the plasma emissions of the process enabled to detect material changes in the plasma plume. This novel method has the advantage of higher sampling rate combined with reduced costs compared to a spectrometer and is thus able to capture the process dynamics.

This paper describes a novel method to analyze the effect of the fiber laser induced plasma on welding of dissimilar Al and Cu. Based on spectroscopic studies, specific wavelengths were found to be suitable for process monitoring during laser welding. For aluminum, the double peak at 394.4 and 396.1 nm was studied, for cu the 578 nm peak was studied. The characteristic peaks were observed by multiple photodiodes equipped with narrow optical filters with varying FWHM. Analyzing the plasma emissions of the process enabled to detect material changes in the plasma plume. This novel method has the advantage of higher sampling rate combined with reduced costs compared to a spectrometer and is thus able to capture the process dynamics.

Aluminum and Copper were joined using the laser-based braze-welding process. By avoiding the intermixture of both conductive materials, the formation of brittle intermetallic compounds is strongly reduced. This results in a tough, ductile connection with reduced electric resistance. This paper describes a method, which is based on the 4-wire method, to measure the resistance of the weld seam. The arrangement of the conductive electrodes directly on top and bottom of the weld seam significantly increases the accuracy of the measured resistances, thus offers a direct estimation of the inter-metallic layer thickness. The electric measuring of the layer thickness is a non-destructive method, which assists in the reduction of the post-process effort (cross sections, pull tests, hardness measurements) and decreases the lead-time by reducing the time needed for the identification of suitable laser process parameters.

Aluminum and Copper were joined using the laser-based braze-welding process. By avoiding the intermixture of both conductive materials, the formation of brittle intermetallic compounds is strongly reduced. This results in a tough, ductile connection with reduced electric resistance. This paper de-scribes a method, which is based on the 4-wire method, to measure the resistance of the weld seam. The arrangement of the conductive electrodes directly on top and bottom of the weld seam signifi-cantly increases the accuracy of the measured resistances, thus offers a direct estimation of the inter-metallic layer thickness. The electric measuring of the layer thickness is a non-destructive method, which assists in the reduction of the post-process effort (cross sections, pull tests, hardness measure-ments) and decreases the lead-time by reducing the time needed for the identification of suitable laser process parameters.

Aluminum and Copper were joined using the laser-based braze-welding process. By avoiding the intermixture of both conductive materials, the formation of brittle intermetallic compounds is strongly reduced. This results in a tough, ductile connection with reduced electric resistance. This paper de-scribes a method, which is based on the 4-wire method, to measure the resistance of the weld seam. The arrangement of the conductive electrodes directly on top and bottom of the weld seam signifi-cantly increases the accuracy of the measured resistances, thus offers a direct estimation of the inter-metallic layer thickness. The electric measuring of the layer thickness is a non-destructive method, which assists in the reduction of the post-process effort (cross sections, pull tests, hardness measure-ments) and decreases the lead-time by reducing the time needed for the identification of suitable laser process parameters.

Aluminum and Copper were joined using the laser-based braze-welding process. By avoiding the intermixture of both conductive materials, the formation of brittle intermetallic compounds is strongly reduced. This results in a tough, ductile connection with reduced electric resistance. This paper describes a method, which is based on the 4-wire method, to measure the resistance of the weld seam. The arrangement of the conductive electrodes directly on top and bottom of the weld seam significantly increases the accuracy of the measured resistances, thus offers a direct estimation of the inter-metallic layer thickness. The electric measuring of the layer thickness is a non-destructive method, which assists in the reduction of the post-process effort (cross sections, pull tests, hardness measurements) and decreases the lead-time by reducing the time needed for the identification of suitable laser process parameters.

The thermal joining of Aluminum and Copper is a promising technology towards automotive battery manufacturing. The dissimilar metals Al-Cu are difficult to weld due to their different physicochemical characteristics and the formation of intermetallic compounds (IMC), which have reduced mechanical and electric properties. There is a critical thickness of the IMCs where the favored mechanical properties of the base material can be preserved. The laser braze welding principle uses a position and power oscillated laser-beam to reduce the energy input and the intermixture of both materials and therefore achieves minimized IMCs thickness. The evaluation of the weld seam is important to improve the joint performance and enhance the welding process. This paper is focused on the characterization and quantification of the IMCs. Mechanical, electrical and metallurgical methods are presented and performed on Al1050 and SF-Cu joints and precise weld criteria are developed.

Laser welding of dissimilar metals such as Aluminum and Copper, which is required for Li-ion battery joining, is challenging due to the inevitable formation of the brittle and high electrical-resistant intermetallic compounds. Recent research has shown that by using a novel technology, called laser braze-welding, the Al-Cu intermetallics can be minimized to achieve superior mechanical and electrical joint performance. This paper investigates the robustness of the laser braze-welding process. Three product and process categories, i.e. choice of materials, joint configurations, and process conditions, are studied. It is found that in-process effects such as sample cleanness and shielding gas fluctuations have a minor influence on the process robustness. Furthermore, many pre-process effects, e.g. design changes such as multiple layers or anodized base material can be successfully welded by process adaption. The minimization of the interface gap is identified as the most significant influence of process stability. The specimen were validated by mechanical lap shear tests and metallographic analysis.

The thermal joining of Aluminum and Copper is a promising technology towards automotive battery manufacturing. The dissimilar metals Al-Cu are difficult to weld due to their different physicochemical characteristics and the formation of intermetallic compounds (IMC), which have reduced mechanical and electric properties. There is a critical thickness of the IMCs where the favored mechanical properties of the base material can be preserved. The laser braze welding principle uses a position and power oscillated laser-beam to reduce the energy input and the intermixture of both materials and therefore achieves minimized IMCs thickness. The evaluation of the weld seam is important to improve the joint performance and enhance the welding process. This paper is focused on the characterization and quantification of the IMCs. Mechanical, electrical and metallurgical methods are presented and performed on Al1050 and SF-Cu joints and precise weld criteria are developed.

Laser welding of dissimilar metals such as Aluminum and Copper, which is required for Li-ion battery joining, is challenging due to the inevitable formation of the brittle and high electrical-resistant intermetallic compounds. Recent research has shown that by using a novel technology, called laser braze-welding, the Al-Cu intermetallics can be minimized to achieve superior mechanical and electrical joint performance. This paper investigates the robustness of the laser braze-welding process. Three product and process categories, i.e. choice of materials, joint configurations, and process conditions, are studied. It is found that in-process effects such as sample cleanness and shielding gas fluctuations have a minor influence on the process robustness. Furthermore, many pre-process effects, e.g. design changes such as multiple layers or anodized base material can be successfully welded by process adaption. The minimization of the interface gap is identified as the most significant influence of process stability. The specimen were validated by mechanical lap shear tests and metallographic analysis.