Characterization of Nuclear Materials and Fuels with Advanced X-ray and Neutron Techniques: X-ray Diffraction/Scattering II
Sponsored by: TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Nuclear Materials Committee
Program Organizers: Xuan Zhang, Argonne National Laboratory; Jonathan Almer, Argonne National Laboratory; Maria Okuniewski, Purdue University; Joshua Kane, Idaho National Laboratory; Donald Brown, Los Alamos National Laboratory; J. Kennedy, Idaho National Laboratory; Arthur Motta, Pennsylvania State University

Monday 2:00 PM
March 15, 2021
Room: RM 51
Location: TMS2021 Virtual

Session Chair: Arthur Motta, The Pennsylvania State University; Xuan Zhang, Argonne National Laboratory

2:00 PM  Invited
In-situ Investigation into The Stability of Hydride Phases in Zirconium: Fei Long¹; Nima Badr¹; Matthew Topping¹; Igor Cherubin¹; Jun-Sang Park²; Mark Daymond¹; ¹Queens University; ²Advanced Photon Source
    High energy synchrotron x-ray diffraction in-situ heating/cooling has been used to study the dissolution/precipitation behavior of hydrides in Zr and its alloy systems. The stability of hydride phases, in particular the commonly observed delta and gamma hydrides, were studied by thermal cycling under a slow temperature ramp, in pure Zr, Zircaloy-2, and Zr-2.5Nb alloy. It is found that gamma phase is the low temperature stable phase in the binary Zr-H system, with delta phase precipitating first as the high temperature phase. In Zr alloys, however, the stability of delta extends down to room temperature; if there is any transformation to gamma it appears very sluggish. In-situ hydrogen ingress tests were conducted for a Zr-2.5Nb sample with hydride layer on two lateral surfaces, through which the memory effect of hydride precipitation is addressed.

2:30 PM
In-situ Synchrotron X-ray Diffraction Study on Tensile Deformation of Neutron Irradiated Fe-Cr-C Alloys: Hoon Lee¹; Xiang Liu²; Mark Warren³; Dominic Piedmont¹; Xuan Zhang⁴; Meimei Li⁴; Jeff Terry³; Jonathan Almer⁴; James Stubbins¹; ¹University of Illinois at Urbana-Champaign; ²Idaho National Laboratory; ³Illinois Institute of Technology; ⁴Argonne National Laboratory
    The investigation of mechanical deformations in Ferritic/Martensitic (F/M) steels is important for the development of fast fission and fusion reactor systems. In-situ XRD tensile experiments have provided valuable information on deformation behavior of these alloys with specific data as a function of crystal orientation of the Fe matrix and carbides. This includes microstructural information regarding dislocation density and type and precipitation resulting from neutron-induced atomic displacement damage. Irradiation hardening with lattice deformation of the matrix and carbide phases have been evaluated by analyzing wide angle X-ray scattering (WAXS). The evolution of edge and screw dislocations have been calculated by using the modified Williamson-Hall (MWH) method. The evolution of radiation induced precipitation and void growth have also been analyzed with small angle X-ray scattering (SAXS). The results of the study will provide theoretical and quantitative analysis of irradiation hardening behavior with microstructural information in Fe-Cr-C model alloys.

2:50 PM
Microstructural Characterization of the Stress and Strain Deformation Partitioning Evolution in Tungsten Heavy Alloys: David Sprouster¹; M. E. Alam²; G. R. Odette²; L Snead¹; ¹Stony Brook University; ²UCSB
    Tungsten is generally too brittle to serve a structural function. However, the fracture toughness of 90 to 97 wt.%W Fe-Ni liquid phase sintered tungsten heavy alloys (WHAs) is typically 10 to 20 times larger than monolithic W. These WHAs are composed of 30 痠 W-particles embedded in a continuous surrounding thin walled honeycomb ductile fcc Fe-Ni-W phase matrix. The superior WHA toughness involves new mechanisms associated with arrest, blunting and bridging of numerous dilatational shielding process zone W-particle scale microcracks, that sustain large amounts of plastic deformation, even in the W-constituent. Here, both laboratory and synchrotron-based x-ray techniques are used to characterize the in-situ evolution of local constituent stress and strain, their multiaxial stress states, as well as dislocation structures and damage, in tensile specimens loaded to near rupture. This unique database will be key to developing rigorous models of the remarkable new toughing mechanisms operating in WHA.

3:10 PM
Creep Behavior of Advanced Austenitic (Fe-25Ni-20Cr) Alloy 709 through In-situ Neutron Diffraction Characterization and Transmission Electron Microscopy Characterization: Yuchen Zhao¹; Ryan Schoell¹; Matthew Frost²; Djamel Kaoumi¹; ¹North Carolina State University; ²Oak Ridge National Laboratory
    Advanced austenitic alloy 709 (Fe-25Ni-20Cr) is a promising candidate as a structural material for advanced reactors like the sodium cooled fast reactors. The various types of precipitates which can form in the material can offer superior creep strength. Accelerated pseudo-creep tests with temperatures ranging from 500 ˚C to 900 ˚C and stresses ranging from 50 MPa to 150 MPa were conducted to probe the creep behavior of the material in situ under neutron diffraction. The evolution of the dislocation density was determined using a modified Williamson-Hall analysis. The creep curves were analyzed using the Bird-Mukherjee-Dorn equation to identify the dominant creep mechanism as dislocation climb. Post-experiment transmission electron microscopy was then used to confirm dislocation climb as well as identify the precipitates involved in the creep mechanism at the various temperature and stress conditions.

3:30 PM
Using In-situ Synchrotron X-ray Scattering to Determine the TTT Diagram of U-6Nb: Nathan Peterson¹; Jianzhong Zhang²; Don Brown²; Bjorn Clausen²; Eloisa Zepeda-Alarcon²; Erik Watkins²; Elena Garlea³; Sean Agnew¹; ¹University of Virginia; ²Los Alamos National Laboratory; ³Y-12 National Security Complex
    The U-Nb system exhibits a rather complex phase transformation landscape, including metastable phases which form by both martensitic and diffusional transformation mechanisms. It is known that the high temperature BCC solid solution phase of U-6 wt% Nb is not stable at room temperature, and at higher temperatures (300-600蚓), the phase transformation process begins within seconds. Rapid, in-situ synchrotron x-ray diffraction and small angle scattering measurements have been performed on U-6Nb samples in order to develop accurate time-temperature-transformation(TTT) data for this material. Of special interest in this study is determining the time to the “nose” of the TTT diagram. Complicating factors in the analysis include the presence of multiple phases with the same BCC crystal structure but each having distinct levels of Nb in solution.