Intergranular Corrosion Behavior of the Friction-stir-welded Joint of 7N01S-T5 Aluminum Alloy Plate
FANG Zhenbang1,2, ZHANG Zhiqiang1,2, LI Ying1,2, YIN Hua3, XING Yanshuang4, HE Changshu1,2
1 School of Materials Science and Engineering, Northeastern University, Shenyang 110819 2 Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110819 3 Research & Development Center, CRRC Changchun Railway Vehicles Co.Ltd., Changchun 130062 4 CRRC Qingdao Sifang Locomotive Vehicle Co.Ltd.,Qingdao 266111
Abstract: In this work, the intergranular corrosion tests were conducted for the vertically-sliced samples of a friction-stir-welded (FSW),14 mm-thick 7N01s-T5 aluminum alloy plate, and OM, TEM were employed to determine the intergranular corrosion behavior of different areas of the joint. The results showed that the different locations in welded joint have various corrosion morphology after intergranular corrosion test. The heat-affec-ted zone (HAZ) of the weld exhibits the highest susceptibility to intergranular corrosion, in which the top and the bottom surface layers suffer more serious corrosion than the central layer. This can be ascribed to the continuously dispersed precipitates on grain boundary and the grain size. The thermo-mechanically affected zone (TMAZ) is a transition zone locating between the heat-affected zone and the stir zone, and characterized by a highly deformed structure. However, TMAZ is relatively less susceptible to intergranular corrosion, owing to the thermal cycle it experienced and the partial re-dissolving of the precipitates on the grain boundary. The stir zone (SZ) experiences severe plastic deformation and temperature cycling during FSW process, which results in a fine grain equiaxed structure, and in consequence, complete re-dissolving of the precipitates. Hence SZ can be considered most insensitive to intergranular corrosion.
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