Materials Systems for the Future of Fusion Energy: ODS Steel and Tungsten Alloy Development
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee, TMS: Additive Manufacturing Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Jason Trelewicz, Stony Brook University; Kevin Field, University of Michigan; Takaaki Koyanagi, Oak Ridge National Laboratory; Yuanyuan Zhu, University Of Connecticut; Dalong Zhang, Pacific Northwest National Laboratory
Thursday 8:30 AM
March 3, 2022
Room: 203A
Location: Anaheim Convention Center
Session Chair: Iver Anderson, Iowa State University Ames Laboratory; Eric Lang, University of New Mexico
8:30 AM
NOW ON-DEMAND ONLY - Fabrication of an Oxide Dispersion Strengthened Ferritic Steel Using SolidStir Technology: Pranshul Varshney1; Kumar Kandasamy2; Nilesh Kumar1; 1University of Alabama; 2Enabled Engineering
The reactor core components for advanced fission and fusion reactor applications demand enhanced elevated temperature properties and radiation damage tolerance. Oxide dispersion strengthened (ODS) ferritic steels are often candidate materials for this purpose. Mechanically alloyed 14YWT (Fe–14Cr–3W-0.4Ti-0.3Y2O3 (wt. %)) is one of such nano-structured ODS ferritic steels suitable for advanced fission and fusion reactor applications. However, this material faces very limited manufacturing methods due to its metallurgical attributes. To circumvent the current processing limitations, an innovative process SolidStir that is designed based on the Friction Stir Welding/Processing (FSW/P) principles will be demonstrated for consolidation and fabrication using mechanically alloyed 14YWT powder. The innovative aspect of the work is combining two proven material processing technologies to fabricate nano-structured ODS ferritic steel structures directly into more useful structural forms. Microstructural characterization results of the alloy consolidated using SolidStir processing technique will also be presented.
8:50 AM Invited
Promoting Oxide Dispersion Strengthening in Ferritic Steels Made with GARS Powder for High-shear Powder Consolidation and for L-PBF: Iver Anderson1; E. Cockburn1; T.R. Riedemann1; Ralph Napolitano1; 1Ames Laboratory (USDOE), Iowa State University
Instead of mechanical alloying that needs days of milling and suffers from contamination, and inhomogeneity, oxide dispersion strengthened (ODS) ferritic alloys, e.g., “14YWT,” were generated with powders from gas atomization reaction synthesis (GARS) of molten Y-containing alloys and a mildly oxidizing atomization gas, producing a Cr-enriched surface oxide. Microscopy of GARS powders revealed that a metastable oxide layer (<50nm) forms on the rapidly solidified powders, controlled by oxygen concentration and droplet cooling during solidification, linked to particle size. If hot isostatic pressed at <800C, trapped powder surfaces become oxygen reservoirs that are released on heating above ~900C for reaction with Y-containing intermetallic compounds within each particle, forming highly stable oxide dispersoids. In this work, alloy composition and O2 levels were varied specifically for consolidation either by solid-state friction/stir shearing with indirect extrusion or by laser-powder bed fusion to enhance oxide dispersion strengthening. Support from USDOE-ARPA-E through Ames Lab contract DE-AC02-07CH11358.
9:20 AM
Alternative ODS Steel Manufacturing with Gas Atomization Reaction Synthesis (GARS) and Friction-based Processing: Dalong Zhang1; Jens Darsell1; Glenn Grant1; Iver Anderson2; Xiaolong Ma1; Jing Wang1; Danny Edwards1; Wahyu Setyawan1; Takuya Yamamoto3; Robert Odette3; 1Pacific Northwest National Laboratory; 2Ames Laboratory; 3University of California-Santa Barbara
Oxide dispersion strengthened (ODS) steels are promising structural materials for future fusion reactors. The high-density (~1023/m3) of highly stable Y-(Ti)-O nano-oxides provide high sink strength for radiation resistance and high-temperature (> 650 °C) creep strength. Concomitantly, helium management is enabled by trapping high density (~1023/m3) of small (< 3 nm) helium bubbles in the vicinity of nano-oxides. However, conventional route of making ODS steels involves prolonged ball milling, canning, and laborious thermo-mechanical processing (TMP). GARS method has demonstrated the potential of making precursor ODS steel powders without ball milling, but the nano-oxide density was below 1022/m3 in the final consolidated form by conventional TMP. Taking advantage of GARS precursor powder, we use friction-based processing, including friction consolidation and/or friction extrusion, to manufacture ODS steel with further improved nano-oxide characteristics and mechanical properties. Preliminary results showed that Y-containing surface oxides and intermetallic particles were effectively refined due to severe deformation.
9:40 AM
In-situ TEM of the Microstructure and He Behavior of AM W Alloys: Eric Lang1; Ian McCue2; W.S. Cunningham3; Jason Trelewicz3; Khalid Hattar1; 1Sandia National Laboratories; 2Northwestern University; 3Stonybrook University
Tungsten-base materials are the plasma-facing materials (PFMs) of choice for future fusion devices for their high Z and melting point. Future reactor designs are expected to require complex additively manufactured (AM)components, which poses processing challenges for tungsten. AM-W components are riddled with cracks due to solidification, cooling shrinkage, and passing through its ductile-to-brittle transition. This team has successfully fabricated dense, low-defect AM-W by developing custom AM alloy formulations. Unlike traditional wrought processing, W is fully melted during AM, which drives the formation of new microstructures with nanoscale, second-phase inclusions. In addition to increasing mechanical strength, these inclusions can potentially increase the material’s radiation-damage tolerance. In this talk, we present multiscale SEM and TEM microstructural characterization of these new materials. In addition, we carry out in-situ TEM irradiation and heating to probe the real-time incubation behavior of He bubbles.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
10:00 AM
Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys: Sean Mascarenhas1; David Sprouster1; Chad Parish2; Jason Trelewicz1; 1Stony Brook University; 2Oak Ridge National Laboratory
Grain size refinement and the introduction of compositional complexities provide unique opportunities for tungsten, which while largely considered to be the primary divertor armor material for future fusion devices, remains limited by instabilities under extended exposure to the anticipated harsh conditions of the fusion environment. Here, we present a synergistic alloy design strategy for combating structural instabilities in tungsten and characterize the microstructural transitions during powder metallurgical processing of bulk nanostructured tungsten alloys. Through lattice Monte Carlo modeling, we map compositional complexities in the W-Ti-Cr system and their dependence on temperature. Using these design maps, a series of ternary nanostructured tungsten alloys are subsequently synthesized through high energy ball milling with microstructural evolution characterized through synchrotron x-ray diffraction. Finally, we demonstrate bulk alloy synthesis through field assisted sintering and show that the deliberately designed tungsten alloys consolidate to near-full density at markedly reduced sintering temperatures relative to pure coarse-grained tungsten.