Abstract
The paper deals with the evaluation of the shielding gases influence on the porosity of AZ31B magnesium alloy weld joints produced with disk laser. Butt weld joints were produced under different shielding gas types, namely Ar 4.6, He 4.6, Ar + 5 vol.% He, Ar + 30 vol.% He. Light and electron microscopy, computed tomography, microhardness measurements and tensile testing were used for evaluation of weld joints properties. He shielded weld joints were the narrowest ones (1.79 mm). On the other hand, Ar shielded weld joints exhibited the largest weld width (2.11 mm). The choice of shielding gas had significant influence on the porosity level of welds. The lowest porosity was observed in weld joint produced in Ar 4.6 shielding atmosphere (only 0.05 mm³), while the highest level of porosity was detected in weld joint produced in pure He 4.6 (0.41 mm³).

Key words
laser welding, AZ31B magnesium alloy, AZ61 filler wire, porosity

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