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Summary
The CO2 laser welding of A3003, A7N01, A5052 and A5182 aluminium alloys, was carried out at different welding speeds and laser powers. The behaviour of porosity in the laser welds was investigated to make clear the mechanism of porosity formation. Three types of porosity of more than 20 μm in diameter were observed. According to the analysis of porosity gas in the laser welds of aluminium alloys, hydrogen was about 60 to 80 vol% of the total gas, with the rest being nitrogen and helium. For the laser welds of Al-Mg alloys, most small pores were formed along the solute band with magnesium enrichment, since magnesium had higher solubility for hydrogen in the liquid state than pure aluminium.
It is concluded that porosity formation is greatly influenced by the magnesium content of Al alloys and hydrogen owing to the interaction of hydrogen and magnesium.