Spatial beam oscillation during laser beam welding of aluminum to copper was investigated. The beam was spatially oscillated perpendicular to the direction of feed in a sinusoidal mode. The influence of the oscillation amplitude and frequency on the weld seam geometry and the implications on the electrical resistance of the joints was investigated. It was found that spatial beam oscillation allows to set the welding depth and seam width virtually independent of each other. Furthermore, low welding depths into the lower copper sheet in combination with high ratios of seam width at the interface of the two sheets to welding depth into the lower copper sheet result in low electrical resistances of the welds. Low electrical resistances were found to correlate with high mechanical strengths of the welds.

Laser cutting of metals is one of the most common applications in industrial manufacturing. Due to this, every improvement of process efficiency and the consequential increase of cutting velocity while maintaining the quality implies a high economic potential. A key factor influencing the maximum cutting speed is the distribution of the absorbed laser power which depends on the polarization state of the incident laser beam. This work presents experimental results obtained with a radially polarized CO2 Laser with an output power of 3700W. These results are compared with results from cutting with a standard circularly polarized beam. The investigation is focused on the different behavior of the cutting process due to the different polarization states. The emission spectra of the cutting front were measured with a spectrometer with high spatial resolution. The temperature was determined by fitting a Planck black-body radiation to the calibrated continuum emission. The temperature measurement has an accuracy of ±100K and a spatial resolution of 136 measurement points along the cut front. The temperature profiles of the cutting front are shown to be different for the two polarizations. This difference is supposed to be the reason for the observed difference in the resulting cutting edge surface.

An analytical model to predict the extent of the heat-affected zone in laser-welded dissimilar materials with strongly differing thermal properties is presented. The model applies to the joining of two materials, where the heat-affected zone occurs in the joining partner with low thermal responsivity. Heat is supplied to the joining partner with high thermal responsivity and heat conduction is the only mechanism of heat transfer. The model is applied to the laser welding of solid nickel sheets to sheets of nickel foam. With a deviation of less than 1.5%, the extent of the heat-affected zone predicted by the model is in excellent agreement with the ones determined experimentally.

Laser powder bed fusion (PBF-LB) is increasingly adopted for producing complex aluminum components for lightweight aerospace and automotive applications. However, its broader application is limited by the relatively low fatigue strength of as-built parts. Adjusting the microstructure and mechanical properties of PBF-LB parts to increase their fatigue strength remains a key research focus. Most research concentrates on conventional heat treatment methods which affect the components microstructure globally and are time- and energy-expensive. In contrast, laser heat treatment (LHT) enables to locally tailor the microstructure and mechanical properties efficiently. Still, the potential of LHT for PBF-LB manufactured aluminum components and the underlying mechanisms remain largely unexplored. Therefore, this study investigates the microstructural evolution of PBF-LB manufactured AlSi10Mg parts subjected to a post-PBF-LB LHT. The influence of the key process parameters - laser power, relative movement speed of the laser beam on the part (feed rate), and beam diameter – on the microstructure and hardness – as well as the resulting mechanical properties are evaluated. Hardness, tensile strength, and fatigue performance are compared to the as-built and T6 heat-treated condition. The findings reveal that after LHT the microstructure closely resembles that of conventionally stress-relieved material. The controlled coarsening of silicon particles facilitates dislocation movement, allowing the tuning of hardness and ductility. LHT achieves tensile strengths comparable to T6 heat-treated specimens while offering increased ductility. In the low-cycle fatigue regime (< 1E5 load cycles) LHT specimens achieve the lowest fatigue strength due to the retained heterogenic scan track structure facilitating crack propagation. In the high-cycle fatigue regime (1E5-1E7 load cycles), LHT-treated samples demonstrate improved fatigue strength compared to the as-built condition and equal to T6 treatment owing to a superior defect tolerance. Overall, LHT provides an effective approach for localized microstructural adjustment and tuning of mechanical properties, representing a promising approach to achieve tailored part properties for PBF-LB manufactured parts.

Temporally resolved temperatures and their gradients were measured in the weld pool during power modulated laser welding of copper to aluminum. A spectrometer and two pyrometers were used to measure temperatures with a high sampling rate of 5 kHz. When welding with a modulation frequency of the laser power of 50 Hz the measured temperature signals show periodic oscillations that correspond to the frequency of the laser power modulation.