Study On Joint Properties And Milling Deformation Analysis Of The Dissimilar Joined Plate For Mg And Al Alloys

In aerospace manufacturing industry, reducing aircraft weight is an important issue. An important and effective solution is joining different alloy plates used as a large-scale structure. Joining technology and status of residual stress in the joining zone have a profound impact on the subsequent milling. In this paper, dissimilar alloy plates were joined by friction stir joining technology(FSJ) and 2024-T3 aluminum alloy and AZ31 B magnesium alloy were selected as the study objects. On this basis, the milling technology to joined dissimilar plate was studied. The main work and the achievements accomplished in this article are listed as following:1. FSJ material flow process and joint forming mechanism were analyzed.Eccentric squeeze flow process for FSJ joint material flow was established and the process was verified by the test method. From this process, some corresponding inferences have been obtained and verified.2. Mg/Al dissimilar alloys FSJ process force on tools measurement and analysis.Tool forces were measured in 3 directs to FSJ process using 3.2mm Mg/Al dissimilar alloy plates and the impacts to the tool forces for technology parameters were analyzed. The mathematical models of tool forces were established, and then the experimental values were compared to mathematical model values and verified the correctness of the mathematical models of tool forces.3. Study on Mg/Al dissimilar alloys FSJ technology parameters and analyze the impact of technology parameters on the joint mechanical properties.FSJ experiments studies were did for Mg/Al dissimilar alloys and the technology parameters range was determined. Mechanical properties were testes for Mg/Al dissimilar FSJ joints of different technology parameters. Within the range of technology parameters, there is inverted "V" shape relationship between tool rotation speed and mechanical properties of the joint, and it also showed between tool feed speed and mechanical properties. Microstructure and morphology analysis were did for Mg/Al dissimilar FSJ joints and the fact that metal compounds of Mg17Al12 and Al3Mg2 are produced in the Mg/Al dissimilar alloys FSJ process was determined by EDS energy spectrum analysis and XRD phase analysis. The joint tensile fracture morphology was observed. FSJ joint fracture mode in tensile test and cause of crack source produced were determined. Microhardness analysis was produced for Mg/Al dissimilar FSJ joints.4. Study on tools offset in Mg/Al dissimilar alloys FSJ process.Offset tools in Mg/Al dissimilar alloys FSJ process, and then analyze the mechanical properties ofMg/Al the offset joints in order to find the optimal offset amount of in the process. There is inverted "V" shape relationship between tool offset and mechanical properties of the joint and the highest point of inverted "V" shape is located to the offset to the aluminum side 0.5mm. Metal compounds of Mg17Al12 and Al3Mg2 are produced in the Mg/Al dissimilar alloys FSJ joint which joined use tool offset way.5. Study on temperature field numerical simulation of Mg/Al dissimilar alloys FSJ process.The FSJ process heat source model base on the variable of tool rotation speed and tool feed rate was established, and used it for numerical simulation of FSJ process. The thermal cycling curves obtained from experiment measurements and numerical simulated were compared, which can authenticate each other. The effect of technology parameters to temperature varieties in the FSJ process was analyzed.6. Analysis of residual stress distribution and deformation principles in Mg/Al dissimilar FSJ joints.The FSJ sheet residual stress and deformation distribution were studied by experiment and the effect of technology parameters to residual stress distribution and deformation principles in the FSJ process was analyzed.7. Analysis of residual stress distribution and deformation principles in the milled Mg/Al dissimilar plates which joined by FSJ.The effect of milling technology parameters to residual stress distribution and deformation principles in the milled Mg/Al dissimilar plates which made by FSJ were analyzed by milling experiment. The optimal milling parameters were obtained.