Optimisation of process parameters and tooling during friction stir welding of AA2024-T3

Abstract

Friction stir welding (FSW) was invented and experimentally proven at The Welding Institute (TWI) in 1991. The process involves the joining of two metal pieces without melting by joining their molecules together. The tool traverses along the joint causing sufficient frictional heat to soften the material without melting. The rotation of the tool then stirs the molecules together leaving behind a fully consolidated joint. Because it is a solid state process and joining takes place below the melting temperature of the material, a high-quality weld is created with many advantages over fusion welding techniques. However, one of the main advantages of the process is its ability to weld 2xxx series and 7xxx series aluminium alloys which are used extensively within the aerospace industry, but are generally non-weldable using fusion welding techniques. FSW provides a solution to welding these alloys and an alternative to riveting. The overall aim of the project was to optimise the operational parameters and tooling design, and also to provide a comprehensive understanding of the FSW process during the welding of AA2024-T3 plates. This was achieved through the development of a processing window for various operational parameters; testing of new tooling designs and the comparison of their performance to traditional FSW tooling; characterisation of the forces and temperatures generated and the development of a FE model to simulate the process.