Microstructure in the FSW Butt Joint of Aluminum Alloy AA5083

Abstract

The weight reduction for vehicles is the great expectations for energy saving and environmental preservation. Aluminum alloys will utilize and be helpful very much in some steel structure of vehicles to reduce their weight. Friction Stir Welding (FSW) is a novel material joining technique, which can produce superior mechanical properties in the weld zone. As compared to conventional welding, FSW consumes considerably less energy. No shielding gas or flux is used, thereby making the process environmentally friendly. The joining does not involve any use of filler metal and therefore any kind of aluminum alloy can be joined without concern for the compatibility of composition, which is an issue in fusion welding. In this paper, two plates of aluminum alloy AA5083 were FSW in the butt joint for tensile test and TEM observation on stir zone. The specimens for TEM are chosen from the cases of the ultimate tensile strength of FSW butt joint over 300MPa and larger than 86% of the base material. TEM field images show that the microstructures in the stir zone of FSW joint were recrystallized grains in micron-meter order and submicron-meter order, and fund amorphous within stir zone of welds. Boundaries of grains are not definable that is uncommon phenomenon.