Analysis of self-reacting friction stir welds in a 2024-T351 alloy

In this study the GKSS force controlled self-reacting unit has been employed to produce welds in a 4mm thick 2024-T351 aluminium alloy plates. Three pins geometries were investigated for their suitability in joining the workpieces. Processing temperatures were measured in both sides of the welded joint at a depth of 1mm from the top and bottom surfaces of the plates. Microhardness testing indicated that considerable thermal softening occurs in each side of the joint. A comparison of welding forces, welding temperatures and microhardness measurements performed in the same alloy for similar FSW parameters, produced using standard FSW technique indicates that the self-reacting welds have higher processing temperatures with slightly lower welding forces for both in the weld travel and transverse to the welding direction. Temperature development in self-reacting FSW has been analysed using the iSTIR code enabling to assess heat losses and heat power dissipated during welding.