Study Of The Organization And Properties Of Vacuum Electron Beam Welded Joints Of WE43 Magnesium Alloy

As a lightweight alloy material,magnesium is widely used in various industries for its low density,good thermoforming,good electromagnetic shielding properties,good casting properties and easy recycling.And WE43 magnesium alloy is one of the most widely used magnesium alloys,belongs to a rare earth magnesium alloy,its main rare earth elements are Y,Nd,Gd,Zr,at room temperature tensile strength can reach272MPa,application temperature can reach 240?,has good strength and very low density,is an important engineering application materials.There are many welding methods available for magnesium alloys,but in this paper we have chosen to use the vacuum electron beam welding method for the welding of magnesium alloys.Vacuum electron beam welding has a very high energy density,a concentrated heat input and operates in a high vacuum environment,which overcomes problems such as inclusions created by gases in the air that chemically bond with the material.In order to explore the influence of vacuum electron beam welding technology on the microstructure and properties of WE43 rare earth magnesium alloy,finite element simulation method was used to simulate the temperature field of vacuum electron beam welding of WE43 rare earth magnesium alloy with a thickness of 4mm,so as to find the optimal process parameters for electron beam welding of WE43 rare earth magnesium alloy.Through the scanning electron microscope,X-ray diffractometer,tensile testing machine and other equipment,comparative study WE43 rare earth magnesium alloy base material and electron beam welding joints of microstructure and properties.The purpose is to provide some theoretical basis for the application of vacuum electron beam welding technology for magnesium alloy in practical production.The result shows that:(1)Based on SYSWELD software,the WE43 magnesium alloy vacuum electron beam welding model was drawn and a combined heat source model of a double ellipsoidal heat source plus a vertebral Gaussian heat source was established to numerically simulate the WE43 magnesium alloy vacuum electron beam welding process and analyse the temperature field clouds.Then the welding speed was optimized and it was concluded that the plate was welded through at a welding speed of10mm/s and the welding efficiency was the highest.At the same time for experimental verification,the test results and simulation results are basically the same,indicating the reasonableness of the choice of vacuum electron beam welding simulation heat source and the feasibility of welding speed optimization,simulation results are reliable.(2)Using the optimized vacuum electron beam welding process parameters for WE43 magnesium alloy electron beam welding,WE43 magnesium alloy plate was completely welded through,and the surface of the weld without deformation,well formed.The weld cross-section is a typical upper wide and lower narrow wedge shape with a melt depth of 3.95mm,a melt width of 1.81mm on the upper surface and a depth to width ratio of 2.18.(3)Vacuum electron beam welding can refine the grain size of WE43 magnesium alloy welds,resulting in a significant refinement of the grain size in the center of the weld.During the electron beam welding process,the weld metal melts and reaches its boiling point,and the decrease in the percentage content of Mg elements in the weld leads to a relative increase in the percentage content of Y,Zr,Nd and Gd elements.WE43 rare-earth magnesium alloy base material and weld are present in?-Mg matrix and?-Mg₂₄Y₅ second phase,?-Mg is the main phase,and the peak intensity of its diffraction peak is higher than that of?-Mg₂₄Y₅ second phase.(4)After the vacuum electron beam welding treatment of WE43 magnesium alloy,the tensile strength of the joint is 237MPa,slightly higher than the base material,the yield strength is 94MPa,equal strength match with the base material,elongation is11.8%,slightly higher than the base material.The weld shows a slight increase in tensile strength and yield strength compared to the base material.The fracture morphology of the weld fracture has tearing ribs and more dimples,indicating a mixed ductile and brittle fracture mode.The average microhardness of the welds obtained after electron beam welding of WE43 magnesium alloy is about 27%higher than that of the base material area,and the highest microhardness is found near the centerline of the weld.(5)The wear of both WE43 magnesium alloy base material and electron beam welded joints is dominated by abrasive wear and accompanied by some spalling wear.The average friction coefficient of welded joints(0.065)is smaller than the average friction coefficient of base material(0.081),which indicates that the wear resistance of welded joints has improved and the friction performance has improved.The self-corrosion potential maps,AC impedance spectra,polarization curves and corrosion morphology of WE43 magnesium alloy base material and electron beam welded joints show an increase in corrosion resistance at the weld seam compared to that of the base material.These studies not only provide insight into understanding the effects of vacuum electron beam welding on the microstructure and mechanical properties of WE43magnesium alloy,but also provide valuable information for the development and manufacture of WE43 magnesium alloy products in practical applications.Figure[55]table[13]reference[96]...