Study On Friction Stir Welds Of Bullet Train Aluminum Alloy

Friction Stir welding is a new solid-state connection technology, which can effectively avoid drawbacks, appeared during fusion such as crack and blowhole. It has the strong superiority on the similar metal and dissimilar metal with worse weldability.The object of this research was to investigate the characteristics of joining, microstructures, microhardness, tensile properties and fracture of FSW joints welded for experimental aluminum alloys, such as 5083-H321 and 6082-T6 and the influence of welding parameters including most importantly the tool's rotational speed, welding velocity, and tool's geometries on the quality of joint according to the solid-state joining principle during FSW welding.Finally, the materials under experimental optimal welding parameters condition were completed on correlative studies, in these welding parameters, the tensile strength of FSW 5083 butt-joint achieved about 94.5% of that of parent metal, and 6082 butt-joint achieved about 73.3% of the parent metal because the 6082 aluminum belong to age-hardness aluminum; Effect of dissimilar material orientation on FSW joint properties is that the joint in which 6082 Al-Alloy was located on advancing side shows a higher tensile strength than that of 5083 Al-Alloy on advancing side. The study results show that the FSW heat-input depends on the ratio of the rotating speed and welding speed, and then, affected the tensile strength of joint: when the heat-input was excessive, the HAZ will became wider, and the temperature of the joint zone was reached the melting point of the parent material, and local melt phenomena will be appeared; and when the heat-input was overmuch little, there were point and tunnel flaws in the joint, even the groove flaws was appeared on the joint surface, the tensile strength decreased.The results of investigations provide data for FSW welding experiment, accelerate the application of FSW in bullet train aluminum alloy in our nation.