Effects of Solution Heat Treatment on Friction Stir Welding Joints of 7B04-O Aluminum Alloy

doi:10.3901/JME.2015.22.035

Abstract

Abstract: The aero Al-coating 7B04-O aluminum alloy plates with the thickness of 3 mm are subjected to friction stir welding (FSW), the effect of solution heat treatment on the microstructure and tensile property of the FSW joints are investigated. The results show that, with the rotation rate of 800 r/min, the welding speed of 200 mm/min and the shoulder diameter of 12 mm, sound FSW joints with no defect are obtained. Dynamic recrystallization take place in the nugget zones(NZs) with fine and equiaxed grains generated. After the heat treatment, the abnormal growth of grain is found in both the upper and the bottom parts of the NZs, whereas the fine equiaxed grains in the center part is retained. During the tensile test, the fraction position occurs in the base metal of the welded joint. The ultimate tensile strength of the welded joint is 198 MPa, which is equal to that of the base metal. the breaking elongation is about 13.2%. After the solution heat treatment, the tensile strength and breaking elongation of the FSW joint are about 310 MPa and 11.2% respectively, and the joint fails in the NZ during the tensile test, which shows incomplete ductile fracture.

Key words: 7B04 aluminum alloy, friction stir welding, heat treatment, mechanical property, microstructure

HAN Peipei, YANG Chao, WANG Jijie, DU Baorui, LIU Xiaohan, XUE Peng, MA Zongyi, NI Dingrui. Effects of Solution Heat Treatment on Friction Stir Welding Joints of 7B04-O Aluminum Alloy[J]. Journal of Mechanical Engineering, 2015, 51(22): 35-41.

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