Atom probe tomography applied to the analysis of irradiated microstructures
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With its particular ability to image solute clusters in three dimensions and impurity segregation to selected interfaces and grain boundaries, atom probe tomography has provided unique insight into the effects of irradiation on materials microstructures. This article reviews the contribution of atom probe tomography to our understanding of behaviors and responses of structural materials under irradiation. Possible atom probe tomography based approaches and common data analysis methods to analyze the microstructural features often observed in irradiated materials are described. In particular, the analysis of solute clustering, solute segregation, and void imaging are discussed in the context of radiation-induced hardening of austenitic steels and reactor pressure vessel steels, and the development of oxide dispersion strengthened steels, radiation-induced solute segregation to grain boundaries for stress corrosion cracking or corrosion issues, and to understand the swelling response of irradiated materials. While highlighting the unique information that atom probe tomography can offer, common limitations, current challenges, and outstanding technical questions regarding data analysis and interpretation are also presented.
I. INTRODUCTION
Monitoring the evolution of properties of materials subjected to irradiation is a crucial aspect of nuclear safety. Irradiation can induce significant microstructural changes that have been associated with dramatic changes in properties such as fracture toughness, strength, ductility, propensity to stress corrosion cracking, or corrosion resistance.1 Predictive models would in theory be used to ensure the appropriate selection of materials and inform on the lifetime of components by capturing the relationships between irradiation conditions imposed by specific reactor designs and resulting microstructure and property changes. Fracture toughness tests and characterization of materials retrieved from active or decommissioned plants as well as surveillance programs have indeed generated large amounts of information and knowledge regarding the behaviors of irradiated materials, and steels in particular, and informed on possible extended lifetime operation (e.g., Ref. 2). However, characterization of microstructures to a level of accuracy required for predictive models remains a challenge, in part due to the large number of variables (alloy composition, impurity levels, processing, irradiation conditions, etc.) that complicate the interpretation of the experimental data. The very small scale of the microstructural features formed in irradiated materials also stretches the limits of most Contributing Editor: Joel Ribis a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.398 J. Mater. Res., 2014
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characterization techniques. Despite these challenges, high-resolution characterization techniques, which include transmission electron microscopy (TEM), small angle neutron scattering (SANS), and atom
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