Study of the optical emissions during Nd:YAG laser welding of AA5182

In this paper broad band spectroscopic measurements of the CW Nd:YAG laser welding process of AA5182-H111 are discussed. This specific alloy is e.g. used for the production of Tailor Welded Blanks in the automotive industry. For many optical sensor applications it is important to know the spectral content of the welding process, as such information is crucial for the selection of optical filters. The measurements were conducted in the range of 600 to 1600 nm. Measurements were conducted in two different configurations. In the first configuration the angle between the workpiece and the optical axis of the optical system used for the measurements was 15°. In the second configuration this angle was 75°. In both configurations 16 measurements were taken and the results were averaged. In this way the influence of the fluctuating overall intensity of the weld plume was reduced. However these fluctuations still remain the main source of noise in the measurement results. It was found that the region between 1000 and 1600 nm was dominated by temperature radiation. In the region of 700 to 1000 nm a broad band peak was seen that is quite distinct from temperature radiation. There were many peaks found in the measured spectra that correspond with wavelengths at which atomic emission lines are present of Ar, Al, Mg, N and O atoms. However no vibrational or rotational emission lines of AlO, MgO, AlH, N₂ or O₂ could be detected.