Dual-beam irradiation of friction stir spot welding of nanostructured ferritic oxide dispersion strengthened alloy

Friction stir spot welding (FSSW) is a very promising technique for the joining of oxide dispersion strengthened (ODS) materials without oxide particle agglomeration and loss in mechanical properties in the weld zone. Heating and severe plastic deformation can significantly alter the originally as-received material. The local microstructure determines the weld mechanical properties, which are analyzed by nanointendation. The FSSW region consists of three different zones: the base material, the thermo-mechanically affected zone and the heat affected zone. Irradiation of the FSSW area was performed with a Fe+/He+ dual ion beam. Hardness changes within the welding zones and variation with irradiation damage are discussed.