Research on the Zigzag-curve in Friction Stir Welding Joints for LY12 Aluminum Alloay
|School||Nanchang University of Aeronautics and|
|Course||Materials Processing Engineering|
|Keywords||Friction Stir Welding LY12 aluminum alloy S-curve Plasticized metal flows Mechanical properties|
LY12 aluminum alloy is the superior performance of high-strength aluminum alloy, widely used in the aerospace, automotive, shipbuilding and other industries. Its welding with conventional welding technology, easy to produce cracks, holes, welding deformation and other defects. The subject of LY12 aluminum alloy plate friction stir welding, to observe and analyze the effects of mixing needle shape, the S-curve of the welding parameters and mixing needle offset weld formed regular, while the S-curve on the joint performance of provide the basis for this type of high-strength aluminum alloy joint control of the S-curve has practical significance to the development and application of FSW. S curve is the butt surface oxide is accompanied by the flow of plasticized metal is formed, continuous in the longitudinal direction of the weld. SEM shows that the S-curve formed from the hole-intensive, continuous holes to form S-curve similar to the cracks. EDS analysis of the main component of the S curve is the oxygen and aluminum. Stirring needle shape the formation of the weld S-curve. The threaded needle stir welding, the weld is not easy to S-curve; smooth stirring pin welding, butt surface material is easy to form the S-curve. When the welding speed is constant, the higher the speed of rotation of the mixing head or a certain rotation speed, welding speed, no longer appear smooth stir the pin welding of weld S-curve. Was stirred for glossy cylindrical pin, when the welding speed is constant, the head rotational speed increases stirred weld S curve crosses the centerline of the needle was stirred horizontally in the direction extending to the forward edge distance decreases, the S curve of the angle increases. With stirring pin offset increases to the forward section of the S-curve distance extending horizontally in the direction of the forward edge is reduced, and while moving to the return, and the S curve is not continuous to ultimately throughout the weld cross-sectional view; with stirring pin offset increases to the return section of the S-curve is gradually moved to the forward edge, throughout the area increases along the direction of thickness of the weld. Stirred for glossy tapered pin, when the welding speed is constant, increasing the mixing head rotation speed, the S-curve to weld the forward edge extending horizontally distance decreases, the vanishing point in the process of extending downwardly from the upper and the bottom of the weld distance increased large. When a certain speed of rotation of the mixing head, reducing the welding speed, mostly in the forward side of the S-curve, decreases in the thickness of the weld direction throughout the region. Tapered smooth stirring pin bias forward edge welded, the S curve variation cylindrical glossy stirring pin bias S-curve variation of the forward edge welding. The presence of the S-curve affect the the joint fracture characteristics. S-curve of tensile test specimens along the weld nugget in the S-curve fracture section was \Split bending test, the sample along the weld nugget in the S-curve of the S-curve and S-curve sample is curved in the center of the weld crack initiation, back bending along the forward edge of the weld toe clad layer crack initiation .