Joint characteristics and dissimilar materials joining of pure-Al/5083 by friction stir welding

摘要

Defects can be detected by radiographic examination for a joined material of pure Al and 5083, bonded by means of friction stir welding, depending upon the welding conditions even though welding is performed by altering the material arrangement. It is necessary to establish the optimum welding conditions to obtain sound weld zones. Observation of the macrostructure revealed that pure Al and 5083 were intricately mixed at the weld zone. Furthermore, it became evident, from the results of x-ray diffraction and EPMA analysis, that pure Al and 5083 are not solid soluble and were merely mixed each other. Observation of the microstructure of weld cross-sections revealed that the rolled structure of the base metal was recrystallised and the crystal grains were coarsened at the weld zone of the pure Al side. Furthermore, it was shown that with a faster travelling speed, the coarsened region was further deceased. It became evident that the crystal grains of 5083 were miniaturised compared with those of the base metal and a region which was assumed to have undergone plastic flow. From measurement of the hardness distribution, a region was noted in the pure Al side where the hardness 364-was reduced compared with that of the base metal. This was caused by the softened, rolled, pure Al base metal during welding. The results of tensile testing of joints showed that, in every case fracture took place at the region where the pure Al hardness declined. Furthermore, no difference in the tensile strength due to the variation in the travelling speed was note.