Analysis of Thermal Fields, Weld Strength and Microstructural Studies of Friction Stir Dissimilar Weldments of AA6082 and AA7075

Abstract

This research work aims to investigate thermal fields, weld strength and microstructural analyses of dissimilar welded structures of AA6082 and AA7075 developed using friction stir welding process. Three different tool shapes were used for joining of these plates to study the effect tool profiles on thermal cycles and their behavior on weld strength. The process parameters were considered same for three tool weldments. During welding, peak temperatures and their distribution towards along transverse direction and cooling temperature were recorded using Infra-Red (IR) thermography. The samples were inspected were X-ray radiography test to examine the defects. The tensile strength of the welded structures was evaluated by conducted tension test according to ASTM E/8 standards. Further, the microstructural behavior for three tool profile pins was studied using optical microscopy. The tool profile with cylindrical shape exhibiting higher tensile strength than the other two samples due to lower temperatures and uniformity of heat distribution during welding process. Also, the microstructural studies revealed that the fine grains with proper mixing zones were observed when cylindrical tool was employed. From this research work, IR thermography is most suitable for measuring In-situ temperature profiles even at weld vicinity during welding.