Research On Forming And Flow Characteristics Of 7055 Aluminum Alloy VP-TIG Arc Additive Manufacturing

At present,in civil aircraft,the amount of aluminum alloy material accounts for60% to 80% of the weight of the aircraft itself.7055 aluminum alloy has super high strength.7055 super aluminum alloy is used to replace 7050,7B04 and other500 MPa high-strength aluminum alloys.Manufactures of main load-bearing components such as wing panels and stringers on aircraft can significantly reduce the weight of the structure by about 10%.The use of arc additive technology to manufacture 7xxx aluminum alloy structural parts can realize production automation and product integration,and high raw material utilization.In this paper,the forming problems of arc additive manufacturing of 7055 aluminum alloy and the numerical simulation of the flow behavior of the molten pool were studied.Firstly,the forming laws of single-pass multilayer and multi-channel single-layer samples were studied.For single-pass multilayer deposition,a prediction model for the forming size of the stable zone and deposition process parameters is established.The prediction model is verified by experiments to predict single-pass multilayer The accuracy of the sample forming size is high.Finally,the influence of the deposition process parameters on the sample forming size is analyzed;the influence of the deposition process parameters on the maximum inclination angle of single-layer multi-pass forming is explored;for multi-layer multi-pass welding,an improved variable-spacing lap model is proposed,and the proposed model is verified through experiments.When multiple layers and multiple samples are deposited by this model,the lap can be formed well.Then,on the basis of the process test,a numerical simulation study was carried out on the flow behavior of the molten pool in the single-pass arc additive process.It is found that the change of the deposition current has a great impact on the size of the molten pool of single-pass single-layer deposition.With the current increasing,the clockwise vortex in the molten pool gradually becomes smaller.In the longitudinal section,the clockwise vortex in the molten pool increases as the deposition current increases,and the center position of the vortex keeps moving backward.When the deposition rate is low,there are two flow patterns in the molten pool on the cross section: the counterclockwise vortex at the bottom of the molten pool and the clockwise vortex that occupies most of the molten pool.As the deposition rate increases,the counterclockwise vortex at the bottom of the molten pool gradually disappears.The preheating temperature has little effect on the size of he molten pool,mainly affecting the formation at the arc starting point.In the calculation of single-pass multilayer arc deposition,deposition is performed on an arch-shaped substrate.As the deposition current increases,the slumping tendency of the liquid metal to both sides becomes more obvious,and the center of the vortex clockwise on the cross section gradually moves toward the surface of the molten pool.The upward component of the liquid metal flow velocity on the central area of the molten pool increases.When the deposition rate is low,the phenomenon of the molten pool flowing and bulging to both sides is more obvious,and there is no vortex flow in the longitudinal section.The increase of the preheating temperature is conducive to the transition between layers during single-pass multilayer deposition.As the temperature increases,the convex corners of the lower edge of the molten pool gradually become smooth.In the inclined deposition procedure,there is a clockwise vortex inside the protruding molten pool and the liquid metal on the right surface flows downwards,and the inside flows vertically upwards.The main force that can maintain the inclined deposition is surface tension,because of which the liquid metal below the arc flows horizontally in the direction of the original deposited metal.Finally,the process of multi-channel arc additive manufacturing was simulated.It is found that under typical deposition parameters,the flow of liquid metal on the right side of the molten pool in the cross-section was mainly dominated by electromagnetic force.While on the side close to the original deposited metal,the liquid metal flows from high to low to the center of the molten pool under the action of gravity,and the flow in the longitudinal section varies with the section on the left and right of the arc center plane.With the increase of the deposition current,the size of the molten pool increases,and at the same time the arc force and electromagnetic force increase,causing the surface of the molten pool directly under the arc to collapse significantly increasing the height difference with the original deposited metal side and the effect of gravity It is also obvious.As the deposition rate increases,the volume of the molten pool decreases significantly,especially the width of the layer decreases significantly.When the deposition rate is low,there are two eddies in the molten pool,which are the clockwise vortex at the tail of the molten pool and the counterclockwise vortex that occupies most of the molten pool.As the deposition rate increases,the clockwise vortex at the tail of the molten pool disappears,and the clockwise vortex becomes larger.The preheating temperature has little effect on the size of the molten pool.