Executive Summary : | The 5xxx series alloys, which are potential alternatives to steel in transport vehicle structures due to their good weldability and high specific strength, are being explored as lightweighting options to reduce emissions and increase fuel efficiency. However, these alloys suffer from low temperature sensitization due to grain boundary precipitation of the electrochemically active (Al3Mg2) ? phase. During fabrication, they are exposed to weld thermal cycles, which can lead to intergranular corrosion followed by stress corrosion cracking (SCC). The degree of sensitization (DOS) values are approximately 200% higher than the base alloy, and the nucleation of ? phase precipitates at grain boundaries is also likely depending on the welding process parameters. The project aims to identify the zones of the friction stir welded Al5059 alloy most susceptible to IGC/SCC from among the complex heterogeneous zones developed after post-FSW sensitization. It also aims to optimize FSW process parameters of tool rotation and traverse speeds by studying their effect on the evolution of post-FSW sensitized microstructures and corrosion susceptibility. The study will also study the stress corrosion cracking response of welded and sensitized Al5059 alloy and understand the underlying damage mechanisms. The "post-welding" sensitization and SCC studies are scarce in scientific literature, but they could be invaluable in ensuring the reliability of welded Al5059 alloy structures. |