Research On Microstructure And Mechanical Properties Of Marine Aluminum Alloy Arc Additive Manufacturing

The application of aluminum alloy in the marine field is mainly due to its good corrosion resistance,good weldability,high strength,and light weight,which can cope with various complex environments in navigation.Therefore,aluminum alloys have many applications and developments in the shipbuilding industry.Wire arc additive manufacturing takes an electric arc as a heat source and an inert gas such as argon as a shielding gas.During the arc heating process,the wire is continuously melted,and the wire is deposited layer by layer along the planned path to form metal structure.Wire arc additive manufacturing technology has the characteristics of low manufacturing cost,high manufacturing efficiency,and high material utilization.First of all,this article adopts gas tungsten arc welding technology,with ER5356 aluminum alloy wire as the material.Through the research on the forming process of single layer single pass welds,the quadratic regression equation of single layer single pass weld forming dimensions was established.The order of influence of single process parameter and interaction of two process parameters on weld width is obtained.The effect of process parameters on the weld width is as follows: travel speed> welding current>wire feed speed>arc length.The effect of process parameters on the weld width is as follows: travel speed>wire feed speed>welding current>arc length.And get the optimal process parameters:the welding current is 100 A,the wire feed speed is 140cm/min,the travel speed is 30cm/min,and the arc length is 5mm.Secondly,the influence factors and laws of anisotropy of mechanical properties were studied by arc additive manufacturing of aluminum alloy wall.The content of alloying element Mg is not only decreased in the arc additive manufacturing process,but also its distribution is not uniform.The content of Mg in the center zone of each layer of the arc additive manufacturing wall is lower than that in the adjacent remelting zone.In order to observe the microstructure of the additive wall,heat treatment was carried out.The crystal grains near the fusion line of one layer and the substrate are columnar crystals,and the crystal grains in the center area and remelting zone of the other layers are equiaxed grains.And the grain size in the center zone of each layer was larger than that in the adjacent remelting zone.When there are no inter-layer defects such as pores and cracks in the arc additive manufacturing wall,the uneven distribution of alloying elements and the difference of microstructure lead to anisotropy of mechanical properties.The maximum tensile strength of the transverse specimen is 267.6MPa,which is 30.9MPa higher than that of the longitudinal specimen.The maximum fracture elongation of the transverse specimen is 33.9%,while the maximum fracture elongation of the longitudinal specimen is 23.8%.The tensile specimens are all plastic fracture,and the Mg content on the fracture surface of transverse specimens is higher than that of longitudinal specimens.Finally,the influence of path planning on structure forming in arc additive manufacturing is studied.Among them,through the research on the forming process of single-layer two-pass welds,it is found that with the increase of the weld spacing,the flatness of the weld surface first becomes smaller and then becomes larger.By verifying the tangent overlapping model,it is found that the optimal weld spacing of single-layer two-pass welds and the weld surface flatness is reduced.In addition,in the trifurcate and cross structures,a continuous deposited path should be set at the center of the Tributary structure to avoid clearance defects as far as possible.The speed of the torch should be increased at the center of the cross structure to reduce the amount of metal accumulation here.