Spectral Analysis of the Plasma in Low-Power Laser/Arc Hybrid Welding of Magnesium Alloy

The previous work indicated that there were interactions between laser beam and arc plasma in low-power laser/arc hybrid welding. In order to study the interactions, the spectra of plasmas in tungsten inert gas (TIG) welding and hybrid laser/TIG welding of magnesium alloy are acquired, and the differences between them are analyzed. In hybrid welding, the intensities of emission spectra of Mg I and Mg II are much stronger than in TIG welding, while those of Ar I and Ar II are a little weaker than in TIG welding. The temporal characterizations of the sensitive lines of Ar I, Ar II, Mg I, and Mg II are studied to investigate the effect of laser beam on arc plasma. In addition, the influence of laser power on the welding quality is investigated, and it is found that the threshold value of laser power which can improve the welding quality is 50-70 W in hybrid welding. Finally, the electron temperature and electron density of welding plasma are estimated, and the interaction between laser and arc is discussed.