Study On Microstructure And Properties Of Welded Joints Of Different Welding Methods Of AZ31B Magnesium Alloy

In recent years,with the continuous development of science and technology,high-speed trains have become the preferred mode of transportation for people's travel due to their short running time and good cabin envirorunent.Metro and fast-track trains in cities have gradually become the preferred mode of transportation for daily travel.This puts higher requirements on the running speed and safety performance of the train.In this context,reducing the quality of the car body or interior parts is the primary problem.Aluminum alloys and magnesium alloys have excellent properties of low density,specific strength and specific stiffness.Aluminum alloys can be used as high-speed train body materials due to their good corrosion resistance,and aluminum alloy bodies have been manufactured and put into operation..Although the density of magnesium alloy is smaller than that of aluminum,the application of magnesium alloy welding is not particularly extensive at present,so improving the mechanical properties of magnesium alloy welded parts has become an urgent problem to be solved.In order to make magnesium alloys such as light alloys widely used in high-speed trains,it is necessary to study the properties of magnesium alloy welded joints.In this paper,the microstructure and properties of TIG welding and friction stir welded joints of 4mm and 6mm AZ31B magnesium alloys were studied and compared.The welding under different welding methods was analyzed by bending,microhardness,metallographic,tensile and pulsating tensile fatigue tests.Joint structure and properties were compared and the microstructure and properties of the welded joints under the two welding methods were compared.Research indicates:The tensile strength of TIG welding and friction stir welding joints of 4mm and 6mm AZ31B magnesium alloys meets the requirements.The fracture positions of all tensile specimens are heat affected zone,and the joints under both welding methods have good tensile properties.The bending angles of the TIG welding and friction stir welding bending specimens of 4mm and 6mm AZ31B magnesium alloys all reached 180°,and the bending properties of the two welding methods were good.The welded joints of AZ31B magnesium alloy under TIG welding and friction stir welding are composed of a(Mg)phase and 3(Mg17Al12)phase,but the distribution and shape are slightly different;4mm and 6mmAZ3 IB determined by pulsating tensile fatigue test The median fatigue limit of magnesium alloy TIG welding head with specified life of 1×107 times is a0.1=70MPa and 75MPa respectively;the median fatigue limit of 4mm and 6mmAZ31B magnesium alloy friction stir welded joints with specified life of 1×107 times are respectively ?0.1=87.5 MPa and 107.5 MPa.