Relation of tensile strength and hardness distribution in friction stir welded joints of ADC12/5052 dissimilar aluminum alloys

Abstract

ADC12 and 5052 dissimilar aluminum alloys have been connected by friction stir welding (FSW). The temperatures at the stir zone and at four points on each outside of the joint line were measured during FSW in various conditions. After FSW, the tensile test was carried out in the direction perpendicular to the joint line. Tensile strength did not depend on the traveling speed, and indicated an almost constant value by about 88% of mother material strength. However, the necking feature in the breaking part was influenced by the traveling speed. That is, the necking was caused at low traveling speeds of FSW while it was hardly caused at high traveling speeds. The two-dimensional hardness distribution in the WD section was measured for various FSW conditions. The material flow with stirring and the spatial difference of the hardness distribution appeared at various traveling speeds. The stirred region consisting of stir zone and thermomechan-ical affected zone and the softened part in the stir zone were wider in the 5052 side at lower traveling speed. Softening in the 5052 side was scarcely observed in high traveling speeds. Moreover, the difference of softening in this 5052 was attributed to a difference in the heat input by changing the traveling speed.