Investigating microstructural evolution in a ball milled ODS 14YWT alloy powder consolidated using friction stir processing technique

There is a need for innovative materials in advanced nuclear reactors expected to operate under much harsher conditions than the current fleet of nuclear reactors. A prospective candidate material for making fuel cladding tubes and other structural elements for next-generation advanced nuclear reactors is the oxide dispersion strengthened (ODS) alloy 14YWT (Fe-14Cr-3W-0.4Ti-0.3Y₂O₃ (wt.%)). Oftentimes, advanced manufacturing processes are required to realize the full potential of such advanced materials. SolidStir^TM Extrusion (patent pending) technology has the potential to overcome the restrictions of the present fuel cladding tube manufacturing process using the ODS alloy. Yet, it is essential to comprehend how processing parameters affect the microstructure of the extruded tube. To that end, closed die compaction experiments were conducted on an Inconel 625 die using friction stir processing to consolidate the ball-milled 14YWT ODS alloy powder under an argon atmosphere. Microstructural characterization carried out using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and transmission electron microscopy shows a close correlation between process parameters and microstructural features. The results on grain size and its distribution, texture, chemical compositions, and nanoscale precipitation as a function of process parameters will be discussed in this presentation. The knowledge gained here will help select processing parameters to control microstructural evolution during SolidStir^TM Extrusion of the fuel cladding tube from the ODS 14YWT alloy powder.