The Research On Friction Stir Welding Process Of Similar And Dissimilar Magnesium Alloy

Friction Stir Welding (FSW) as a new type of solid-phase connection technology with conventional welding methods which has incomparable superiority in the ordinary welding . The FSW of aluminum has been made extensive research and application. Magnesium alloy was known as the 21st century green materials, has broad prospects for development and application. But for a variety of reasons, the magnesium alloy friction stir welding research was less. In this paper, the deformation magnesium alloy AZ31B and AZ61A between dissimilar and same kind of friction stir welding process was researched and the applicable of stir pin was investigated in friction stir welding magnesium alloy. Stir pin of the friction stir welding was the most important process parameters of the FSW. The material, structure and size of the stir pin were the key factors which impact of the properties of forming joint. Through the design of different materials, structure and size of the stir pin for the friction stir welding process of the experiments been done. The appearance of forming horizontal macro-morphology and mechanical properties of the FSW joint was analyzed and compared. The most suitable stir pin for optimization of the experimental material FSW was found.At the same kinds of FSW of AZ61A and AZ31B, the weld forming, joint microstructure, micro-hardness and mechanical properties were analyzed in their various process parameters. The investigations had been carried out on the joint characteristics of the different head rotation speed and welding speed. Through the experiment, the AZ31B and AZ61A achieve the same kind of material friction stir welding and the suitable welding technology of their parameters been gained. Through analysis and comparison, the friction stir welding joints of AZ31B and AZ61A was similar on the whole , but the suitable process parameters of AZ61A joint were narrower than AZ31B joint and the mechanical properties of AZ61A joint were even poorer than AZ31B joint.On the basis of experiments AZ31B and AZ61A in the same kind of friction stir welding material welding process, the two different materials friction stir welding been researched and analysis, as well as welding parameters placement performance of its joints, from the microscopic analysis of the joints in the organization and distribution of the junction of phase composition. The results show that: friction stir welding quality could be achieved AZ31B/AZ61A connection. The maximum tensile strength of joint can reach 90.5% that of the AZ31B base material. The microstructure of joint analysis found that the microstructures of the various regions are very different. When the process parameters was not appropriate the microstructure distribution was layered and wide on the mechanical heat-affected zone, but also there were the concentration of the oxide and the impurity between layered the distribution. The existence of the impure stratum structure and stress concentration was the main reason that caused the drop of mechanical properties on the mechanical heat-affected zone.The result of the investigation proved that the joints of AZ31B, AZ61A and AZ31B/AZ61A magnesium alloy could be successfully carried out by FSW when the optimal welding parameters were chosen. The results, which were of great practical value, not only provided a newly economical and reliable method for joining materials mentioned above, but also established foundation for the further study of FSW techniques. So it had important practical value.