2017 | AFC ACCOMPLISHMENTS 162 Figure 1. Engineering stress-strain curves of the SS-Mini specimens showing their location relative to the stir zone in the 1 mm thick plate of 14YWT. Advanced oxide dispersion strengthened (ODS) ferritic alloys, such as 14YWT, possess excellent high-temperature mechanical properties that are resistant to radiation damage at high dose and temperature exposures, but are considered impossible to weld. Fusion welding relies on forming a melt pool for joining materials, which causes significant coarsening and agglomeration of the nano- oxide dispersion and destroys the ultra-small grain structure of ODS alloys. Friction stir welding (FSW) is a solid-state joining technique that has recently been investigated for welding ODS alloys since it relies on frictional heat generated by a moving pin tool rotating at high speeds and the ODS material for joining. For this reason, the Nuclear Technology Research and Development (NTRD) program began exploring FSW for joining thin plates and ultimately thin wall tubing of 14YWT.This project focuses on developing FSW conditions that avoid defects such as porosity, worm-holes, grain growth and tensile residual stresses that can degrade the joint quality. Complete Status Report Documenting Development of Friction Stir Welding for Joining Thin Wall Tubing of ODS Alloys Principal Investigator: D.T. Hoelzer Collaborators: M.N. Gussev, J.R. Bunn / ORNL