Research On Microstructure And Properties Of AZ91 Magnesium Alloy By TIG Arc Additive Manufacturing Process

Magnesium alloy is one of the metal structural materials with the smallest density.It also has the advantages of good damping performance,strong biocompatibility and large hydrogen storage capacity,so it has a wide application prospect in the field of lightweight.AZ91 magnesium alloy is a typical casting magnesium alloy,which is characterized by high specific strength and corrosion resistance,which is greatly improved compared with pure magnesium.It is mainly used in the shell of electrical products,small-size thin or special-shaped bracket and other fields.At present,the traditional manufacturing methods of magnesium alloy components have the problems of long manufacturing cycle and high cost,so more advanced manufacturing methods are needed.Arc additivie manufacturing is a kind of additive manufacturing technology with wire as filler and welding gun as heat source.It is characterized by simple equipment and low cost.It has been successfully used in additive manufacturing of steel and aluminum alloy large-size components.In this paper,the TIG arc additive manufacturing process and microstructure and properties of AZ91 magnesium alloy were studied.Firstly,the influence of TIG arc additive manufacturing process parameters on the forming quality of AZ91 magnesium alloy was studied.Then,the forming precision control method of thin-walled components and multi-layer and multi-channel thick plate components were explored,and the heat treatment process of magnesium alloy arc additive manufacturing components was discussed The rope.The forming stability of AZ91 magnesium alloy TIG arc additive manufacturing was studied by using high-speed camera.It was found that the best distance between the end of the wire and the substrate was 1 ? 2 mm.When the distance between the end of the wire and the substrate was more than 3 mm,the large droplets which were not easy to fall off would produce repulsive transition.The stability of the front feeding method is the best,and the controllable process window is large.The front feeding can also remelt the defects produced in the additive process and improve the forming morphology.AC duty cycle and AC frequency have little influence on the size of magnesium alloy additive manufacturing,while the current,speed and wire feeding speed have great influence on the size.The forming dimensions of AZ91 magnesium alloy TIG arc additive manufacturing were modeled by design expert software,and the effects of process parameters on the layer width and layer height were explored.Then,the process parameters were optimized based on the model,and the deviation of the layer width of magnesium alloy thin-walled components was reduced from 4.71 mm to 0.95 mm.The effects of different process parameters on the mechanical properties of magnesium alloy thin-walled additive components were compared.When the constant high current additive process parameters were used,the overall mechanical properties of the additive components were more uniform,and the maximum transverse tensile strength was in the middle,which could reach 268MPa;when the variable current additive process parameters were used,the mechanical properties span of the additive components was larger,and the maximum transverse tensile strength was in the middle It can reach 276 MPa.The forming process and mechanical properties of AZ91 Magnesium Alloy by multi-layer and multi-channel TIG arc were studied.It is found that preheating the substrate by delaying the wire feeding time can improve the forming of the deposited metal at the arc starting point and increase the wetting angle;the traditional empirical model of lap spacing and fixed lap spacing are not suitable for Mg alloy TIG additive manufacturing,but when the first center spacing is 5 mm and the subsequent center spacing is 4.5 mm,good forming quality can be obtained.The tensile strength and elongation of the tensile sample along the stacking direction Z are the highest,and the tensile strength reaches the level of forged magnesium alloy,and the elongation is better than that of forged magnesium alloy.The effects of different heat treatment processes on the mechanical properties and microstructure of AZ91 magnesium alloy were studied.The tensile strength and elongation of additive magnesium alloy can be improved by solution heat treatment,and the maximum can reach 301 mpa and 21%.Under low strain loading,the damping property of magnesium alloy decreases with the prolongation of solution heat treatment time.With the increase of aging time,the damping property of magnesium alloy increases gradually.