| Aluminum alloys 6061 and 2024 are widely used in the construction of frames,pipelines and storage tanks in many emerging fields of aerospace industry and marine industry.The heterogeneous connection of alloys 6061 and 2024 is a problem.Riveted connection has its advantages,but it has poor sealing performance and is not easy to be applied in some corrosive environments.The friction stir welding connection(FSW)technology can effectively solve the shortcomings.There are many foreign literatures on 6-series and 2-Series dissimilar aluminum alloy FSW,but few in China.According to the actual situation of domestic aluminum alloy welding,this paper analyzes the influence of welding parameters on 6061 and 2024 FSW joints,so as to provide technical support for practical engineering application.This experiment intends to analyze the influence of stirring head rotation speed on 6061/2024 dissimilar aluminum alloy connection zone through the ratio relationship between stirring head rotation speed and welding speed.(1)Select 5mm thick aluminum alloy plate,select the parameters such as main shaft depression of 0.1mm,main shaft inclination of 2.5°,concave shaft shoulder and conical stirring needle,place 2024 base metal on the forward side for friction stir welding,optimize the test samples,and determine the reasonable stirring head speed and welding speed range.Select the ratio of stirring head speed and welding speed,determine the test parameters,carry out the test,and analyze the joint performance.(2)The metallographic test was carried out on the sample and base metal,and the effects of stirring head speed,welding speed ratio and various parameters on the macro and micro morphology of the joint were analyzed.The test showed that the fluidity of the backward side was significantly higher than that of the forward side material,and the refinement degree of nugget 2024 was higher.Increasing the ?(?=?/v)value will reduce the fusion degree of dissimilar materials in the nugget area.When unchanged,increasing the parameter value can improve the material flow and fusion degree in the nugget area,and the equiaxed grain becomes larger.When the parameter?=1000rpm v=120mm/min,the macro morphology of the joint is the best.(3)The mechanical test of the joint shows that the hardness of the mixed area in the nugget area is between the two base metal hardness,the hardness of unmixed 2024 material is greater than or equal to the base metal hardness,and the hardness of 6061 material is lower than the base metal hardness.With the decrease of heat input,the overall hardness of the joint increases.The integrity of the joint determines the strength of the joint.When the parameter ?=1000rpm v=120mm/min,the shape of the joint is the best,there are no defects,and the tensile strength is the highest,reaching 72%of the base metal.(4)The electrochemical corrosion experiments were carried out on the joints and the base metal under different parameters and the morphology was observed.The polarization curve analysis shows that the corrosion resistance of well-formed joints lies between the two base metals.When the defects of joints increase,the corrosion resistance decreases.The analysis by electron microscopy shows that a large number of corrosives accumulate in the defects such as holes,the structure grain refines and the corrosion resistance improves. |
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