2017 | AFC ACCOMPLISHMENTS 163 Accomplishments: The research goal was to conduct detailed microstructural and mechanical properties characterization studies of the bead-on-plate stir zone produced by FSW in a 1 mm thick plate of 14YWT for developing FSW process parameters that produce high quality welds. The microstructural analysis deter- mined that the FSW conditions for producing the bead-on-plate stir zone (SZ) on the 1 mm 14YWT plate caused slight coarsening of the grain size and theTi-,Y- and O-enriched oxide particles and formation of several horizontal cracks.The slight coarsening of the oxide particles was not consistent with bulk diffusion Figure 2. Specimen #1 from stir zone. (a) Strain distribution (von Mises strain, Green-Lagrange strain tensor) along the specimen gauge at different time (1-5). (b) Experimental tensile curve with force and elongation values for every image. Insert shows superimposed line of DIC analysis on specimen gauge. Project Description: The advanced ODS 14YWT ferritic alloy is being investigated for thin wall fuel cladding in fast nuclear reactor technologies.The goals of this program are to develop fabrication methods to produce thin wall tubing and welding methods to join thin wall tube sections of 14YWT.The latter goal on joining thin wall tubes of 14YWT presents a major challenge due to issues with joining ODS alloys and limited experience with joining ODS alloys by FSW. The main task involves development and optimization of FSW process parameters to ensure weld joints that are defect free and do not degrade the salient microstructural features of 14YWT responsible for the excellent high-temperature mechanical properties and radiation resistance.The objective of this research is the successful joining of plate and tubing of 14YWT with thicknesses less than 1 mm.The knowledge base obtained for joining thin plate and tubing of ODS alloys will be novel since few publications exist on joining ODS alloys by FSW and all these studies used thick plate geometries.This research includes tasks on characterizing the microstructure and assessing the mechanical properties of specimens prepared from the stir zone produced by FSW in a 1 mm thick plate of 14WT. Since the microstructure produced in the stir zone is very complex, a novel approach based on optical extensometry is being explored for studying the local deformation along the gage of miniature tensile specimens from the stir zone during tensile testing. A recent task on measuring residual stresses in hot rolled plates and FSW joints of 14YWT was initiated.The results of this research support the main goal of the fuel cycle Research and Development (R&D) program on developing fabrication methods for producing thin wall fuel cladding from advanced ODS alloys and together will help maximize nuclear fuel utilization of next generation nuclear reactors.