Study On Welding Process Of Non-Consumable Gas Shielded Arc Welding For Magnesium Alloys AZ31B

10 mm AZ31B magnesium metal alloy were welded by TIG and plasma welding process. the microstructure and mechanical properties of the region in the joint were analyzed by the tensile strength, HV hardness, X-ray diffraction testing . Compared the microstructure and mechanical properties of the welding joints , the Gas Tungsten Arc Weld welding process of magnesium alloys was explored.The results showed that: When the Mg alloy was welded by TIG, the microstructure in weld wereα-Mg andα-Mg+Al17Mg12. The HAZ was composed by the coarseα-Mg. When the whole heat input was fixed, the microstructure in weld was decided by the per heat input, the bigger the per heat input, the bigger the microstructure in weld and HAZ. The growing degree was obviously. Even the grain boundary in HAZ would lique locally. When fixing the per heat input, increasing the welding level number, the growing degree of the grain in weld and HAZ was not very big. Increasing the welding level number would not lead to the grain growing level becoming large.The AZ31B thick plates were welded by TIG, the microstructure of joints were uniform, the grain was small, the fusion line was clear. The mechanical properties of the joints were different at different heat input. When the welding speed was stable ,the mechanical properties of the weld using small heat input and large number of multi-layer were higher than the weld using a large heat input and small number of multi-layer. The hardness of the weld was higher than the base metal, The micro-hardness of welding joints using large heat input was bigger than the weld using small heat input. Mg17Al12 is an existence in the weld, The fracture surface was a mixed ductile and brittle fracture feature, means a mixture fracture of cleavage and dimple.The AZ31B magnesium was weld by plasma arc welding , the microstructure of joints was uniform, grain was small, fusion line was clear, there was no existence of heat-affected zone. The magnesium evaporated and burned during the welding process. And other alloying elements were distributed; the regional segregation phenomenon was not serious. The weld was composed by single-phaseɑ-Mg organization, the Mg17Al12 phase or other impurities were not in the weld. The weld hardness is slightly higher than the base metal, the hardness of the weld changed slightly along the depth direction.