Ultrasonic Assisted Friction Stir Welding Process Of2024-T4Aluminum Alloy Sheet

With the development of science and technology, aerospace, military and civilian industry urgently close to the light weight, aluminum alloy sheet is widely used in this kind of engineering. Friction stir welding has its own unique advantages in the welding of aluminum alloy sheet, while the limitation of the friction stir welding, can easily cause the material softened inadequate in the bottom of the weld and poor stability in the welding of aluminium alloy sheet, so it needs to seek new breakthroughts on the the the basis of of friction stir welding.2024-T4aluminum alloy is one of2xxx aluminum alloys which has high strength and good mechanical working properties;and has been widely used in engineering. In this paper,2024-T4aluminum alloy sheet was chosen for representative materials to discover the ultrasonic assisted friction stir welding process of aluminium alloy sheet, expected to solve the problem of thin plate welding.In this paper, Marc finite element software is applied to constuct a three-dimensional stirring friction welding and ultrasonic assisted friction stir welding temperature field model of2024-T4aluminium alloy sheet, which uses contact analysis method and take into account the coupling between the temperature and displacement field, and take into account the influence of the heat of friction heat and plastic deformation. The modle has analysed temperature distribution with and without ultrasound on the same conditions, The results show that wiht ultrasound and without ultrasound weld peak temperature is about510℃and480℃respectively, a difference of30℃. The simulation analysis preliminary give the welding parameters range:the speed1000-2000r/min, welding speed100-400mm/min. The simulation results provide guidance for welding test, and basically agreement with the experimental results.1.8mm thick2024-T4aluminum alloy was adoped in the experiment and appropriate welding parameters of aluminum alloy sheets were explored through a large number of ultrasonic assisted friction stir welding experiments. Some comparative experimints were done between ultrasonic assisted friction stir welding and friction stir welding, through the comparison and analysis of the weld appearance, mechanical properties, microstructure, microhardness and fracture scanning find that the weld properties of ultrasonic assisted friction stir welding is superior to friction stir welding. Experimental results show that on the same welding parameters, ultrasound assisted friction stir welding sample average tensile strength is10%higher and more stable than that of the friction stir welding;the defect rate of friction stir welding is aboat50%, while ultrasonic assisted friction stir welding basically has no defect; the grain of ultrasonic assisted friction stir welding is smaller and more uniform than friction stir welding and the heat affected zone and thermo-mechanically affected zone is significantly reduced comparing to friction stir welding.Experimental results show that ultrasound play a certain positive effects on the weld quality, which can enhance the flow of the metal around mixing head, reduce the weld defect, achieve the effects of grain refinement so as to enhanced mechanical properties, and improved weld quality.