Materials in Nuclear Energy Systems (MiNES) 2021: Material Properties Evolution- Session IV
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory

Thursday 3:30 PM
November 11, 2021
Room: Allegheny
Location: Omni William Penn Hotel

Session Chair: Gary Was, University of Michigan

3:30 PM
Neutron Irradiation Effects on PM-HIP Inconel 625: Caleb Clement¹; Yu Lu²; Sheng Cheng²; Megha Dubey²; Sowmya Panuganti¹; Yangyang Zhao¹; Katelyn Wheeler³; D. Guillen³; David Gandy⁴; Janelle Wharry¹; ¹Purdue University; ²Boise State University/ Center for Advanced Energy Studies; ³Idaho National Laboratory; ⁴Electric Power Research Institute
    The objective of this talk is to understand the effects of neutron irradiation on the microstructure and mechanical properties of Inconel 625 (IN625) fabricated using powder metallurgy with hot isostatic pressing (PM-HIP). PM-HIP presents an attractive alternative to traditional manufacturing methods for use in nuclear applications, however its irradiation response must first be understood. IN625 fabricated with PM-HIP and a traditional forging method were neutron irradiated to a dose of 1 displacement per atom (dpa) at 300ºC in the Advanced Test Reactor. Post-irradiation examination involved bright field transmission electron microscopy (BFSTEM), atom probe tomography (APT), nanoindentation, and in-hot cell tensile testing. PM-HIP IN625 is less susceptible to void nucleation than its forged counterpart, and it additionally shows less irradiation-hardening and embrittlement. The results of this study are a step forward in demonstrating the viability of PM-HIP materials in nuclear applications.

3:50 PM
Influence of Different Heat Treatments and Ion Irradiation on the Microstructural Evolution and Microhardness of Inconel 625 Fabricated via Laser-powder Bed Fusion: Valentina O'Donnell¹; Tahmina Keya²; Mohanish Andurkar³; Ashley Romans²; Greyson Harvill²; Bart Prorok²; Scott Thompson³; John Gahl¹; ¹University of Missouri; ²Auburn University; ³Kansas State University
    The microstructure and microhardness of Inconel 625 fabricated via Laser-Powder Bed Fusion (L-PBF) was investigated in as-printed and heat-treated conditions before and after ion irradiations. Direct proton irradiation in excess of 1014 protons/cm²/s was provided using the cyclotron facility at the University of Missouri Research Reactor Center (MURR). Heat treatment temperatures (between 700 and 1050 ºC) and dwell times (1, 5, and 10 hours) were varied. Results clearly demonstrate that the as-printed Inconel 625 microstructure enables the rapid formation of intermetallic and other precipitate phases well in advance of the established wrought time-temperature-transformation (TTT) diagram. Traditional wrought homogenization procedures are not optimal for L-PBF Inconel 625. Hence, a detailed characterization of grain and precipitate evolution with respect to heat treatment and ion irradiation is provided. Results provide insight into the most appropriate heat treatment for L-PBF Inconel 625 for radiation resistance and/or hardness.

4:10 PM
Mechanical Behavior of Additively Manufactured 316L Stainless Steel and SiC before and after Neutron Irradiation: Thak Sang Byun¹; Timothy Lach¹; Maxim Gussev¹; Annabelle Le Coq¹; Xiang Chen¹; David Collins¹; Gokul Vasudevamurthy¹; Kory Linton¹; Kurt Terrani²; ¹Oak Ridge National Laboratory; ²USNC
    The mechanical properties of additively manufactured (AM) 316L stainless steel (SS) and silicon carbide (SiC) were evaluated before and after irradiation in the High Flux Isotope Reactor to assess the in-reactor performance of AM components. For this research, 316L SS plates were manufactured using the laser powder bed fusion (LPBF) method and SiC disks by a combined process of binderjet 3D printing and chemical vapor infiltration (CVI). Baseline and post-irradiation tensile tests over a wide temperature range of room temperature–600 °C were performed for the AM 316L alloy in different post-build heat-treatment conditions, and room temperature flexural strength testing for the SiC disk specimens in different printing orientations. This presentation is to summarize the outcome of these mechanical tests focusing on the irradiation-induced changes. We will also discuss about the statistical aspect of the strength data for both 316L and SiC materials and the size effect in SiC.

4:30 PM
Plutonium Defect Characterization through Mechanical Deformation: Taylor Jacobs¹; C.A. Yablinsky¹; J.N. Mitchell¹; M.J. Gibbs¹; B.A. Maiorov¹; ¹Los Alamos National Laboratory
    Mechanical deformation is being used to probe defects related to processing and aging in Pu-Ga (1-7 at pct) alloys ranging from 1 to 11 years of age. Stress relaxation measurements were performed using quasi-static compression tests in conjunction with first principles strengthening mechanisms concepts to provide insight into dislocation-defect interactions related to strength. Strength changes associated with grain size, age, and heat treatment conditions were related to measurable changes in the internal and effective stress components of the flow stress. Internal friction was measured using resonant ultrasound spectroscopy to detect Debye peaks related to mobile defects in δ-Pu. Further analysis of the Debye peaks provide the defect activation energy of diffusion and mean residence time, which can help inform material models. Characterization of defects detected by stress relaxation and internal friction will further our fundamental understanding of Pu aging in support of a safe and reliable nuclear stockpile.