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Title:Investigation of mechanical behavior of Alloy 709 for advanced fast reactor applications
Author(s):Piedmont, Dominic Ralph
Advisor(s):Stubbins, James
Contributor(s):Krogstad, Jessica
Department / Program:Nuclear, Plasma, & Rad Engr
Discipline:Nuclear, Plasma, Radiolgc Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
X-ray Diffraction
High Temperature
Stainless Steel
Abstract:The advent of next-generation nuclear reactor systems brings with it a multitude of material challenges. The structural materials to be used for these reactors will be exposed to more extreme conditions of radiation, stress, and temperature than those of prior generations. The development and characterization of novel materials to withstand such environments is a necessity. Alloy 709, developed by Oak Ridge National Laboratory, is a high strength austenitic stainless steel initially designed for boiler tube applications. In this work, the mechanical performance of Alloy 709 was studied using tensile tests with in-situ X-ray diffraction (XRD) at various temperatures, ranging from room temperature (RT) to 600ºC, and displacement rates, from 0.001 to 0.004 mm/s. Using these stress-strain curves, empirical models of Alloy 709’s deformation behavior over a range of temperatures and strain rates were developed. From these models, an optimization of terms was carried out to best characterize Alloy 709’s thermomechanical properties and sensitivity. To establish an accurate empirical deformation model for Alloy 709, subsequent microstructural analysis was completed using the collected in-situ XRD data, Electron Backscattered Diffraction (EBSD) and associated Transmission Electron Microscopy (TEM) analysis. In addition, previous studies have been conducted on the microstructure and mechanical deformation behavior of aged samples of alloy 709. The mechanical deformation behavior of these samples was also modeled using the same equation established to model the behavior of as-received 709. By applying these techniques on the samples, information such as: load partitioning, preferred orientation, presence of secondary phases and their corresponding phase fraction, active dislocation types and their density evolution, all as a function of temperature, was revealed. These techniques functioned to form a complete picture of the development of the Alloy 709 microstructure during deformation and the subsequent changes in deformation behavior due to aging. These results were used to clarify microscopic mechanisms underlying the empirical deformation model.
Issue Date:2020-07-24
Rights Information:Copyright 2020 Dominic Piedmont
Date Available in IDEALS:2020-10-07
Date Deposited:2020-08

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