Microstructure And Properties Of Friction Stir Welding Joints For Aluminum Alloy

Friction stir welding(FSW) is a solid-state joining process which based on the friction welding.This new welding technique with uniqueness and superiority has been paid a great amount of attention by researchers ever since it was developed.So far,the research and development of FSW is still in its initial stage in China,the research of friction stir welding joints microstructure have just begun.In-depth study the effects of various parameters on microstructure of friction stir welding joints,it will provide an important basis for the promotion and application of this technology,establish a rational and effective welding technology.In this paper,the effects of process parameters on microstructure and properties for aluminum alloy 7050-T7451 and 7075-T651 FSW butt joints has been investigated.The results show that it can be forming a joint with a good look and without internal defects when the rotation speed during 400-800rpm and the welding speed during 40-100mm/min for aerospace aluminum alloys 7050-T7451 and 7075-T651.7050-T7451 aluminum alloy in order to speed 400rpm,welding speed 70mm/min for the joint tensile properties than the speed welding for the 40 and 100 mm/min.7075-T651 aluminum alloy in order to speed 600rpm,welding speed 60mm/min for the best joint tensile properties.For 7000 series aluminum alloy,the lowest hardness appears in Thermo-mechanically affected zone of advancing side.This stretch coincides with the location of sample fracture.Materials are rolling the strip plate,after friction stir welding Weld nugget is composed of equiaxed grains,the transition zone stretching deformation of the slab for the organization.The welding nugget area,grain size, heat-affected zone area and grain deformation in TMAZ have increased with the rate ofω/νincreasing.After Heat treatment,the two alloys mechanical properties are improved. Micro-organization also has a better optimization.For the specific performance of the hardness and tensile strength have improved,micro-organization,more refined grains, grain boundary increased by welding the nugget of more refined grains,also increase the intensity of their connection is vital.With the progressive promotion of friction stir welding technology,the microstructure research of FSW request more and more pressing,and aluminum alloy suitable for the FSW a wide range of parameters,the research of microstructure should be more extensive and in-depth.