Study On Microstructure And Properties Of 5A06 Aluminum Alloy Extrusion-arc Additive Interface

With the rapid development of the national high-tech industry,in the aerospace,defense and military industries,more and more components are designed into large-scale structural parts to meet the needs of lightweight,integrated and high-performance,so that aluminum alloy extrusions are widely used.The large-scale integral member is characterized by large size.For example,the deep cavity of the aluminum alloy in this paper has an overall height of more than 500 mm.The overall extrusion molding will face the problem of being unable to demould,and the forming pressure is so large that the ordinary equipment cannot meet the tonnage requirement.In this paper,the large-scale aluminum alloy components are formed by the extrusion-arc additive composite manufacturing technology.The components are divided into two parts according to the structural features.After a part of the hot extrusion molding,the arc is added to a specific surface to obtain a complete components.The extrusion-arc additive connection interface is the key part of the whole component,its combined state,microstructure and mechanical properties play a decisive role in the practicality of the component.In this paper,the parameters of arc additive process are explored,and the structural properties of the composite manufacturing interface are systematically studied to find the optimal process parameters.The arc additive experiment uses a cold metal transition robot flexible welding system to perform arc addition on specific surfaces of different substrates to obtain straight arm body components.Study the arc additive process,and the corresponding process parameters of the additive with good macroscopic morphology and high mechanical properties were determined.The process parameters were adjusted to compare the different process parameters.Exploring the influence law and mechanism of process parameters on the microstructure of additive joint interface.The mechanical properties of the composite manufacturing interface were tested by room temperature tensile test,dimensional microhardness test and impact test.The parts were observed by optical microscope,scanning electron microscope and electron backscatter diffraction.The room temperature tensile properties,dimensional microhardness and impact toughness were tested,grain size and morphology,growth law were observed,and phase composition and grain orientation were analyzed.The process parameters corresponding to the optimal connection interface and the substrate state are determined.Obtained tensile strength reaches 319.15MPa,the elongation can reach21.20%,the dimension microhardness additive zone HV₁80.2,the interface HV₁90.7,the extrusion zone HV₁91,its iMPact toughness is the best,the iMPact energy is 17.95J.The grain morphology and growth mechanism of various parts of the additive were analyzed.The extrusion-arc additive connection interface forms a good metallurgical bond,and its grain characteristics are:one layer of equiaxed fine crystals at the joint,down to the heat affected zone of the substrate,and upward is the first columnar crystal of the additive zone.The grains in the additive zone are alternately distributed between the columnar crystal and the equiaxed crystal.With the increase of the additive height,the columnar crystal characteristics are weakened.By scanning the fracture of the tensile specimen,it is found that the tensile specimen is generally broken in the additive zone,and there are different numbers and different sizes of pores in the additive zone.The pores increase gradually with the increase of the additive height,and no pores are found at the joint interface of the additive members.