| Aluminum alloy are widely used in automotive industry due to low density,high specific strength and specific rigidity,and good elasticity,good mechanical properties.However,fracture occurs at the welding area of aluminum plate which as a structural part of the automotive body,which is caused by defects(cracks,stress concentration)in the traditional welding process of aluminum plates,so a good welding process is the key to ensuring the structural performance of the welded plate,and due to its own welding process principle of friction welding which is promoted to solve the above problems,but the selection of welding process parameters has a great impact on the welding performance.The wrong selection of welding process parameters will cause the material size of the welding area to be coarse and insufficient to flow.At the same time,it will affect the interface strength of the welding area,so cannot meet the needs of actual production and processing.In addition,with certain welding parameters,proper ultrasonic vibration parameters can further improve the performance of welded joints.because ultrasonic vibration can impose an additional heat input for the friction stir welding process,improve the flow capacity of the material in the welding area,change the size of the grain,thus improve the strength of the welded joint.Therefore,according to the above background Firstly,the influence of rotation speed and welding speed on the welding temperature of the workpiece was studied,and then the influence of ultrasonic vibration on the welding temperature of welding tools was studied.Finally,it was verified by AL5754 pressure friction welding experiment.The results showed that: the increase with the welding speed,the decrease of the welding temperature however increase with the rotation speed of the spin increase,the joint flash and peeling disappear when the inclination angle of the stirring head is2.8°.The joint structure is dense and uniform.A small number of pores and inclusions are found in the weld nugget area on both sides of the fusion line.The energy spectrum analysis shows a small amount of alumina.The obvious plastic streamline can be observed under the influence of heat and mechanism.The two base metal structures realize interaction and fusion at the joint.The structure is recrystallized;the tensile strength increases with the increase of rotation speed of the joint.When it is changed to 1080r/min,the joint tensile strength reaches 247 MPa,which is 95% of the base metal strength,and the fracture positions are all located in the heat-affected zone on the side of the sheet.The size of radial-shrinkage and fracture morphology are typical ductile fracture. |
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