Wrought aluminum alloy, A6016, was welded to cast aluminum alloy ADC12 by a friction stir welding (FSW) technique to fabricate dissimilar welds. A6016 was set on the advancing side, while ADC12 was on the retreating side. The tool offset was set to be ±1 mm from the join line. Fatigue strengths of dissimilar welds were lower than that of A6061, but higher than that of ADC12. Fatigue strength increased when the tool was offset into ADC12, which could be attributed to the decrease of risk volume containing casting defects. When ADC12 was set on the advancing side, the fatigue strength of dissimilar weld decreased. Microstructural observation revealed that the macroscopic structure in the stir zone (SZ) drastically changed by putting ADC12 on the advancing side, resulting in the lower fatigue crack initiation resistance and lower fatigue strength.

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A5052 aluminum alloy sheets were formed into concavo-convex shape by friction stir incremental forming. By the conventional friction stir incremental forming, sheet metals were formed from one side and formed into only concave or convex shape without supporting die. But in this study, an equipment for forming from both sides simultaneously was developed and it was tried to form the sheet metals into concavo-convex shape. First, strain distribution by single side forming was measured. To evaluate the forming accuracy by simultaneous forming, formed shapes by double side forming and single side forming with reversing the sheet for forming from both sides were compared. A5052 aluminum alloy sheets with the size of 100 mm x 100 mm x 0.5 mm were used for specimen. From the experimental results, it was conformed that since both sides simultaneous forming is possible to make the two products in one processing, it is possible to shorten the forming time to be half. Curved portion is easy to break. Because Strain of curve portion is bigger than straight portion. Forming accuracy of the center part of the sheet can be improved when the forming of the sheet to close the working distance.

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Friction stir incremental forming is a new sheet forming process that combined incremental forming and friction stir welding together. It can manufacture the hard-to-work material product of complex shape under the traditional CNC machine and only use a hemispherical tool. In most reports using friction stir incremental forming process, sheets were formed into concave shape. On the other hand, sheets were formed into convex shape with simple back support dies by the conventional incremental forming. In this study, sheet metals were formed into convex shape by friction stir incremental forming process with a back support die. A5052-H34 aluminum alloy sheets were used for specimen. The dimension of the sheet was 100 mm x 100 mm x 0.5 mm. A hemispherical stick tool with a diameter of 6 mm was used for forming. The shape of back support die is a frustum of pyramid. The sheet was fixed to the upper face of the back support die by a bolt and formed along the die shape by pushing with the forming tool. Tool rotation rate and fool feed rate were changed and formability was evaluated by the minimum formable wall angle. From the experimental results, formability was maximum and the wall angle was 25 ° when the tool feed rate was 1000 mm/min and the tool rotation rate was 10000 rpm. The formed shapes with and without the back support die were compared. The formed shape with the back support die was closer to the objective shape, especially at the flange part.

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