STUDY OF POROSITY FORMATION IN CO CO2 LASER WELDING OF MAGNESIUM ALLOYS

摘要

The weldability of magnesium alloys, AZ13,AZ31, AZ61 and AZ91 alloys were investigatedusing 2.4kW CO2 laser facility. The wroughtmagnesium alloy welds had very low possibility ofporosity formation. However, the cast magnesiumalloy welds have showed small amount of porosities.The effect of welding speed on amount of porosity ofweld metal and gas-chromatography analysis ofporosity gases were investigated to recognize whichtype of porosity was formed. The experimentalresults have suggested that "B"-type porosity couldbe formed easily by hydrogen and metal vapor.In general, the process of porosity formation byhydrogen in welding may be considered as fourstages including (1) Introduction of hydrogen intomolten pool, (2) bubble formation by hydrogen, (3)the growth of bubbles in molten metal and (4)capture of bubbles in solidified weld metal[1-4].