Study On Forming Process Of Aluminum Alloy MIG Arc Additive Remanufacturing With Transverse Magnetic Field

In recent years,with the rapid development of advanced manufacturing industry,more and more parts and components adopt the overall structure of high-performance,high-reliability and light-weight,so as to achieve the purpose of reducing cost,saving energy and expanding the application field.Aluminum alloy as a light alloy,and have widely used in the manufacturing field because of the low density,good thermal conductivity,good processing performance,good corrosion resistance,high specific strength,and weldability.However,with the increase in service life,a large number of aluminum alloy parts have been damaged to varying degrees.In this paper,in order to improve the repair accuracy and performance of the damaged parts,the influence of external alternating magnetic field on the forming accuracy and microstructure properties of aluminum alloy in the arc additive manufacturing process was studied.In this paper,the orthogonal test method is used to study the influence of various process parameters on the residual height,width and depth of the single weld pass.The results show that,under the condition without magnetic field,the deposition speed has a more obvious effect on the residual height of weld pass,and the wire feeding speed has a more obvious effect on the width and depth of weld pass.Under the condition of magnetic field,the effect of deposition speed on the residual height of weld pass is more obvious,and the effect of magnetic field intensity on the weld pass width is more obvious,and the effect of wire feeding speed on the weld pass depth is more obvious.In addition,the transverse alternating magnetic field can obviously reduce the wetting angle and improve the wetting and spreading performance of the weld.The influence of magnetic field on arc additive forming accuracy is studied in this paper.The results show that when the magnetic field intensity is within a certain range,the surface accuracy of the deposited layer gradually increases with the increase of the excitation current and frequency.When the excitation current is 11 A and the excitation frequency is 14 Hz,the surface flatness of the deposited layer is reaches the maximum of 0.1095 mm.Outside of this range,weld bead appears on the formed surface,and the surface quality decreases obviously.In this paper,the polynomial function curve is used to fit the weld bead profile.At the same time,the optimal overlap amount is calculated based on the flat-top overlap model and verified by experiments.The results show that,the profile of weld bead can be accurately fitted by polynomial function curve.when there is no magnetic field,there are overlapping voids and a large number of pores in the deposited,resulting in lower density of the cladding layer.by adjusting the magnetic field parameters,the overlapping gaps in the deposited layer disappear,the number of macroscopic pores and the size are reduced,and the density has also been significantly improved.The effect of magnetic field on microstructure and properties of aluminum alloy arc additive was studied in this paper.The results show that?(Al)and?(Al₃Mg₂)are the main phases in the deposited layer.under the action of a magnetic field,due to the stirring effect of the arc on the molten pool,the coarse columnar crystals in the structure are interrupted,and the grain size is obvious Refinement.When the excitation current is 11 A and the excitation frequency is 14 Hz,the average hardness reaches the maximum value of 83.9 HV_0.1.when the excitation current is 8A and the excitation frequency is 14 Hz,the tensile performance of the sample is the best,and the average transverse direction of the additive is the maximum tensile strength can reach 275.7 MPa,the maximum elongation is 21.9%,the average tensile strength in the longitudinal direction of the additive is 254.3 MPa,and the elongation is 26.7%.Through the characteristic analysis of the wear morphology and the wear debris morphology,it can be seen that the test Such wear mechanisms are dominated by abrasive wear.Finally,after optimizing the magnetic field parameters,the microstructure and mechanical properties of the formed block samples were characterized.The results showed that,under the absence of magnetic field,there are a large number of columnar grains growing perpendicular to the direction of deposition,and a small number of equiaxed grains in the formed structure.The number of crystals is small,the average microhardness value is 71.3 HV_0.1,the transverse and longitudinal tensile strengths are 220.7 MPa and 258.2 MPa,respectively,and the elongation is11.6%and 22%,respectively.After the magnetic field optimization,the size and number of columnar grains in the formed microstructure are significantly reduced,and the growth directions of grains are different.The average microhardness value is 75.6 HV_0.1,the tensile strength of transverse and longitudinal specimens is 257.8 MPa and 274.2 MPa,respectively,and the elongation is 16.1%and 25.6%,respectively.