Effect Of Al Clad On Electrochemical Corrosion Behavior Of Friction Stir Welding Weld Of Aluminum Alloy

Friction stir welding(FSW) was invented at The Welding Institute (TWI) of UK in 1991 as a solid-state joining technique .The friction stir welding technology is widely applied in the space industry,the orbital transportation and the overland communication industry,the automobile industry and other professions. Meanwhile, many researchers have devoted to systematically investigating the technology and the mechanical properties of FSW joints, the electrochemical corrosion behaviors have been studied relatively scarcely.In the scope of this thesis,influence of Al clad on electrochemical corrosion behavior of friction stir welding weld of 2B06,2524,7B04 and 7075 aluminum alloy have been researched . By static weight loss experiment (gravimetric test),potentiodynamic polarization curve and surface topography analysis(SEM),in the ambient temperature solution of 0.2M NaHSO3 and 0.6M NaCl, corrosion performance was investigated. Then, at the same given experimental conditions,friction stir welding weld and parent metal were comparatively investigated. Meanwhile,the joint of friction stir welding microhardness distribution and microstructure were studied.Test results showed that the microstructure variation of friction stir welding was the main reason for corrosion resistance and microhardness distribution.The microhardness profile of friction stir welding appeared"W"form, microhardness of both parent material was the highest,and softer region of friction stir welding appeared in some particular zones. Static weight loss experiment (gravimetric test) indicated that the corrosion rate of parent material(Al clad) was the least. Scanning electron microscope (SEM) observation showed that a few shallow pits presented on the surface of the FSW weld and parent material(Al clad), however,a large number of deeper pits emerged on the surfaces of parent material.The potentiodynamic polarization curve showed that the corrosion potentials of the parent material(Al clad)were less positive than those of the FSW weld and parent material, meanwhile, the corrosion current density were less than those of the FSW weld and parent material. Friction stir welding weld had more negative corrosion potential and lower corrosion current compared with the base metal.