High-Speed X-Ray Investigation of Pore Formation during Full Penetration Laser Beam Welding of AA6016 Aluminum Sheets Contaminated with Lubricants

Hagenlocher, Christian; Lind, Jannik; Weber, Rudolf; Graf, Thomas

doi:10.3390/app10062077

Cited by 10 publications

(2 citation statements)

References 25 publications

(34 reference statements)

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“…[240] The processes in such welds are difficult to observe experimentally. X-ray radioscopy at up to 250 fps, [241] 1000 fps [242,243] or even 2000 fps [244] has recently been used to unravel the processes in complex weld zones in situ during welding, however, with the usual limitations of radioscopy. As X-ray tomoscopy is now available at high acquisition rates, investigations have been started to study welding in-situ also in 3D.…”

Section: Laser Welding Processmentioning

confidence: 99%

X‐ray Tomography and Tomoscopy on Metals: A Review

et al. 2023

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X‐ray tomography is a versatile tool in materials research and engineering since it allows for a non‐destructive and three‐dimensional mapping of the constituents of a heterogeneous material as long as they differ in their interactions with X‐rays. Recent developments of the technique have brought down the time needed for the acquisition of a single tomogram by many orders of magnitude compared to what was needed 25 years ago. Nowadays, up to 1000 full tomograms can be recorded in a second, which enables real‐time studies of changes in samples caused by reactions or by applied processing operations. The term tomoscopy has been coined for such sequences of 3D images. We review the application of X‐ray tomography and tomoscopy on metals and describe each step required and the associated challenges. A selection of representative investigations is presented with a focus on time‐resolved phenomena in metals and alloys ranging from mechanical deformation, solidification to metals processing processes such as welding and additive manufacturing. Finally likely future developments are discussed.

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Section: Laser Welding Processmentioning

confidence: 99%

X‐ray Tomography and Tomoscopy on Metals: A Review

et al. 2023

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“…Wang et al 7 also came to the conclusion that the best welding results can be achieved with a circular oscillation pattern. According to Wang et al Recent x-ray investigations with up to 1000 fps by Hagenlocher et al 9 show the formation of pores during laser beam welding with disk laser (through-welding) of AA6016 sheets with an intentionally applied oil layer. In this process, rapidly growing gas bubbles appear a few millimeters behind the capillary.…”

Section: Beam Oscillation With Low Frequencymentioning

confidence: 99%

In situ observation with x-ray for tentative exploration of laser beam welding processes for aluminum-based alloys

Börner

Dittrich

Mohlau

et al. 2020

Journal of Laser Applications

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In recent years, laser processes have taken an ever-increasing market share in the manufacture of components. The development of new, improved beam sources with corresponding systems technology and the decreasing investment costs of the beam sources are important keys to this success. Particularly, high frequency beam oscillation has great potential in laser beam welding and cutting. The main obstacle for the widespread breakthrough of high frequency (HF) beam oscillation is the still insufficient understanding of the underlying physical mechanisms. Gaining a deeper insight is essential for process optimization. The in situ observation with x rays enables the visualization and analysis of these highly dynamic processes inside the workpiece. The goal of the performed experiment described in this paper was to in situ analyze the structural evolution of and defect generation in laser welding beads of different aluminum alloys. A fiber laser (max. 600 W, cw output power) including a beam scanner control system for rapid beam guidance was used. Of general interest was the comparison between static and oscillated beam guidance and the effects on the joining procedure. This paper shows the initial results of the analysis of the melt pool behavior and seam formation as well as the formation of seam irregularities during the laser process. In the simplest case, radiographs were taken, i.e., 2D projections of the x-ray absorption coefficient distribution within a material. Thereby, recordings from 10 000 up to 40 000 fps could be generated. Furthermore, tomoscopies-the continuous acquisition of tomographic (3D) images, up to 100 tomograms per second-could be generated with proven equipment, whose main components are a high-speed rotation stage and a camera system. The findings will help to get a better understanding of keyhole phenomena as well as effects of turbulent melt flow such as pore formation and guide to solutions for preventing them. Hence, initial results of high frequency beam oscillation processes including melt pool degassing and porosity reduction will be shown and discussed.

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The change of the absorptance at the transition from partial- to full-penetration laser welding

Wagner,

Hagenlocher,

Weber

et al. 2024

Int J Adv Manuf Technol

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Full-penetration laser welding processes are necessarily associated with significant changes of the geometrical properties of the keyhole at the beginning of the process when the keyhole expands all the way through the workpiece and finally pierces the bottom of the sheet. The impact that this transition has on the absorptance was investigated by means of X-ray imaging to determine the geometry of the keyhole and subsequent raytracing to calculate the distribution of the absorbed irradiance. The results show a significant drop of the overall absorptance when the bottom of the capillary opens through the rear side of the workpiece which in practice is noticed by an unstable behavior of the keyhole. Since the drop of the absorptance is less pronounced for smaller diameters of the keyhole, one may recommend the application of laser beams with small diameters at least during the initial phase until the keyhole is fully developed and reliably reaches through the bottom surface of the welded sheet.

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High-Speed X-Ray Investigation of Pore Formation during Full Penetration Laser Beam Welding of AA6016 Aluminum Sheets Contaminated with Lubricants

Cited by 10 publications

References 25 publications

X‐ray Tomography and Tomoscopy on Metals: A Review

X‐ray Tomography and Tomoscopy on Metals: A Review

In situ observation with x-ray for tentative exploration of laser beam welding processes for aluminum-based alloys

The change of the absorptance at the transition from partial- to full-penetration laser welding

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