Abstract
This paper shows mechanical Properties and behaviors of macrostructures for specimens welded by F.S.W according to welding conditions and tool dimensions with $6.35mm_t$ aluminum 7075-T651 alloy plate. It apparently results in defect-free weld zone in case transition speed was changed to 15mm/min 61mm/min and 124mm/min under conditions of tool rotation speed such as 800rpm. 1250rpm and 1600rpm respectively with tool's Pin diameter 40mm and 60mm. The optimum mechanical property, ultimate stress,${\sigma}_Y=470Mpa$ is obtained at the condition of 124mm/min of travel speed with 800rpm of tool rotation speed using full screw type pin. shoulder dia. $20{\phi}mm$ pin dia. $6{\phi}mm$ and pin length 6mm. The full-screw type and the half-screw type pin shows the similar behaviors of weldability. It is found that the size of nugget is depended on tool transition speed and tool dimension by macrostructures of the cross section of weld zone.
