In-situ 3D high-energy X-ray diffraction study on deformation behavior of neutron-irradiated Fe-9%Cr

Piedmont, Dominic

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https://hdl.handle.net/2142/122096 Copy

Description

Title

In-situ 3D high-energy X-ray diffraction study on deformation behavior of neutron-irradiated Fe-9%Cr

Author(s)

Piedmont, Dominic

Issue Date

2023-10-06

Director of Research (if dissertation) or Advisor (if thesis)

Stubbins, James

Doctoral Committee Chair(s)

Stubbins, James

Committee Member(s)

• Zhang, Xuan
• Heuser, Brent
• Krogstad, Jessica
• DiFulvio, Angela

Department of Study

Nuclear, Plasma, & Rad Engr

Discipline

Nuclear, Plasma, Radiolgc Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Nuclear Materials, X-ray Diffraction, Irradiation damage, HEDM, Machine learning

Abstract

Nuclear power offers a clean, sustainable alternative to fossil fuels that is compatible with the current energy infrastructure. Therefore, significant research has been directed to the development of the next generation of reactors. The higher neutron fluxes and temperature regime of future Gen IV reactors can provide enhance efficiency while improving safety margins. New reactor parameters, in conjunction with the corrosion challenges of new coolants/moderators, create new material challenges. Ensuring the safety of Gen IV reactors requires thorough Investigation and characterization of material properties and behaviors in these extreme environments. Conventionally, materials are characterized at discontinuous lengths scales: electron microscopy captures the micro-scale and tensile test capture bulk mechanical properties at the macro-scale. Often the grain level, or mesoscale, properties and behaviors are accessible. With development of new X-ray technologies, it has become possible to non-destructively probe the mesoscale in three dimensions and in-situ. This study is a first of its kind using High Energy Diffraction Microscopy (HEDM) to investigate a neutron irradiated ferritic/martensitic binary model alloy. Samples of Fe-9wt%Cr were cut into sub-sized tensile bars and exposed in the Advanced Test Reactor (ATR. This study examines two irradiated conditions: neutron irradiated to 0.1 dpa at 300C and 450C, respectively. The tensile properties of these samples along with an unirradiated sample were investigated at the Advance Photon Source (APS) at Argonne National Laboratory (ANL). The far-field (ff) field of view captured the evolution of in-situ aggregate grain properties and behaviors. Together with Crystal Plasticity Finite Element Modeling (CPFEM), a mechanistic understanding of grain rotation and its correlation with grain anisotropy and orientation to the loading direction was extracted. The near-field (nf) field of view captured three-dimensional grain volumes and morphologies. The higher resolution of nf provided localized dislocation and misorientation data to view the deformation properties within individual grains. Coupling the nf and ff datasets enhanced data processing while simultaneously increasing the amount of information possible to view via grain structures and residual stresses in the deformed volume renderings. Parameters from nf were provided to unsupervised machine learning algorithms to aid in data processing and identified useful insights within the dataset. Child domains distribution were established without ff information to improve nf as a standalone technique. Meanwhile, complete sub-grain volumes were identified to increase understanding deformation behavior of individual grains. The research produced valuable material understanding in regard to the effect of radiation on the development of deformation anisotropy and its impact on microstructure and mechanical properties while also developing HEDM as a characterization technique for meso-scale materials performance.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Dominic Piedmont

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