Behaviors of hydrogen and magnesium in porosity formation in CO_2 laser welds

摘要

The CO2 laser welding of aluminum alloys was carried out at different welding speeds and laser powers. And the behavior of porosity in the laser welds was investigated to make clear the mechanism of porosity formation. Three types of porosity of more than 20#mu#m in dia. were observed. According to analysis of porosity gas in laser welds of aluminium alloys, hydrogen was about 60 to 80volpercent of total porosity gases and the rest of them were nitrogen and helium. Besides, for laser welds of Al-Mg alloys, most of small porosity were formed along solute band with Mg enrichment, since magnesium had higher solubility of hydrogen in liquid state than pure aluminum.