Effect of Zinc Coating and Welding Speed on Microstructure of Magnesium/Steel MIG Welded Joint
MIG arc was used as the heat source to connect AZ31 magnesium alloy/Q235 low carbon steel and AZ31 magnesium alloy/DX51D galvanized steel,respectively.By changing the welding speed,the influence of welding speed on the weld formation,microstructure and hardness distribution of AZ31/Q235 and AZ31/DX51D welded joints was studied,and the influence mechanism of zinc coating was revealed.The results show that,the weld for mation of AZ31/Q235 joint is bad.When the welding speed is 10,15 mm/s respectively,the weld formations of the AZ31/Q235 welded joint and AZ31/DX51D welded joint are good.With the decrease of welding speed,the precipitated β-Al12Mg17 phase increases at the weld zone of AZ31/DX51D joint,and the interfacial layer thickness increases.The interfacial bonding of AZ31/DX51D joints is good,while the non-fusion,cracking phenomenons appear at the interface of AZ31/Q235 joints,which shows that the Zn coating effectively promotes the metallurgical bonding of Mg/steel interface.The maximum hardness of the interface of AZ31/DX51D joint reaches 250 HV,which is higher than that of the interface of AZ31/Q235 joint.
MIG fusion brazingmagnesium/steelwelding speedhardness distribution
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