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Title: Detecting the Extent of Eutectoid Transformation in U-10Mo

Abstract

During eutectoid transformation of U-10Mo alloy, uniform metastable γ UMo phase is expected to transform to a mixture of α-U and γ’-U 2Mo phase. The presence of transformation products in final U-10Mo fuel, especially the α phase is considered detrimental for fuel irradiation performance, so it is critical to accurately evaluate the extent of transformation in the final U-10Mo alloy. This phase transformation can cause a volume change that induces a density change in final alloy. To understand this density and volume change, we developed a theoretical model to calculate the volume expansion and resultant density change of U-10Mo alloy as a function of the extent of eutectoid transformation. Based on the theoretically calculated density change for 0 to 100% transformation, we conclude that an experimental density measurement system will be challenging to employ to reliably detect and quantify the extent of transformation. Subsequently, to assess the ability of various methods to detect the transformation in U-10Mo, we annealed U-10Mo alloy samples at 500°C for various times to achieve in low, medium, and high extent of transformation. After the heat treatment at 500°C, the samples were metallographically polished and subjected to optical microscopy and x-ray diffraction (XRD) methods. Based onmore » our assessment, optical microscopy and image processing can be used to determine the transformed area fraction, which can then be correlated with the α phase volume fraction measured by XRD analysis. XRD analysis of U-10Mo aged at 500°C detected only α phase and no γ’ was detected. To further validate the XRD results, atom probe tomography (APT) was used to understand the composition of transformed regions in U-10Mo alloys aged at 500°C for 10 hours. Based on the APT results, the lamellar transformation product was found to comprise α phase with close to 0 at% Mo and γ phase with 28–32 at% Mo, and the Mo concentration was highest at the α/γ interface.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1340892
Report Number(s):
PNNL-SA-120714
DN3001010; TRN: US1701827
DOE Contract Number:
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; DENSITY; EUTECTOIDS; CONCENTRATION RATIO; NUCLEAR FUELS; PHASE TRANSFORMATIONS; IRRADIATION; PERFORMANCE

Citation Formats

Devaraj, Arun, Jana, Saumyadeep, McInnis, Colleen A., Lombardo, Nicholas J., Joshi, Vineet V., Sweet, Lucas E., Manandhar, Sandeep, and Lavender, Curt A.. Detecting the Extent of Eutectoid Transformation in U-10Mo. United States: N. p., 2016. Web. doi:10.2172/1340892.
Devaraj, Arun, Jana, Saumyadeep, McInnis, Colleen A., Lombardo, Nicholas J., Joshi, Vineet V., Sweet, Lucas E., Manandhar, Sandeep, & Lavender, Curt A.. Detecting the Extent of Eutectoid Transformation in U-10Mo. United States. doi:10.2172/1340892.
Devaraj, Arun, Jana, Saumyadeep, McInnis, Colleen A., Lombardo, Nicholas J., Joshi, Vineet V., Sweet, Lucas E., Manandhar, Sandeep, and Lavender, Curt A.. 2016. "Detecting the Extent of Eutectoid Transformation in U-10Mo". United States. doi:10.2172/1340892. https://www.osti.gov/servlets/purl/1340892.
@article{osti_1340892,
title = {Detecting the Extent of Eutectoid Transformation in U-10Mo},
author = {Devaraj, Arun and Jana, Saumyadeep and McInnis, Colleen A. and Lombardo, Nicholas J. and Joshi, Vineet V. and Sweet, Lucas E. and Manandhar, Sandeep and Lavender, Curt A.},
abstractNote = {During eutectoid transformation of U-10Mo alloy, uniform metastable γ UMo phase is expected to transform to a mixture of α-U and γ’-U2Mo phase. The presence of transformation products in final U-10Mo fuel, especially the α phase is considered detrimental for fuel irradiation performance, so it is critical to accurately evaluate the extent of transformation in the final U-10Mo alloy. This phase transformation can cause a volume change that induces a density change in final alloy. To understand this density and volume change, we developed a theoretical model to calculate the volume expansion and resultant density change of U-10Mo alloy as a function of the extent of eutectoid transformation. Based on the theoretically calculated density change for 0 to 100% transformation, we conclude that an experimental density measurement system will be challenging to employ to reliably detect and quantify the extent of transformation. Subsequently, to assess the ability of various methods to detect the transformation in U-10Mo, we annealed U-10Mo alloy samples at 500°C for various times to achieve in low, medium, and high extent of transformation. After the heat treatment at 500°C, the samples were metallographically polished and subjected to optical microscopy and x-ray diffraction (XRD) methods. Based on our assessment, optical microscopy and image processing can be used to determine the transformed area fraction, which can then be correlated with the α phase volume fraction measured by XRD analysis. XRD analysis of U-10Mo aged at 500°C detected only α phase and no γ’ was detected. To further validate the XRD results, atom probe tomography (APT) was used to understand the composition of transformed regions in U-10Mo alloys aged at 500°C for 10 hours. Based on the APT results, the lamellar transformation product was found to comprise α phase with close to 0 at% Mo and γ phase with 28–32 at% Mo, and the Mo concentration was highest at the α/γ interface.},
doi = {10.2172/1340892},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 8
}

Technical Report:

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  • This report presents an automated image processing approach to quantifying microstructure image data, specifically the extent of eutectoid (cellular) decomposition in rolled U-10Mo foils. An image processing approach is used here to be able to quantitatively describe microstructure image data in order to relate microstructure to processing parameters (time, temperature, deformation).
  • A mathematical model that describes the change in shape of T.T.T. curves for ternary-eutectoid steels with various types and contents of alloying elements has been developed by O. Dairiki. This model predicts also the partitioning coefficient of the ternary substitutional element between cementite and ferrite that occurs during austenite-pearlite reaction. The present research concerns experimental aspects and provides us with data that will be used to discuss the validity of the theoretical model. Three different alloying elements were chosen: chromium, nickel, and Mn in combination with Cr. Time-Transformation-Temperature curves for four different chromium eutectoid alloys, one nickel eutectoid alloy, andmore » one chromium-manganese quarternary eutectoid alloy were determined using a dilatometry technique. Transmission electron microscopy was used for microstructure observation and characterization. Evidence of chromium partitioning between cementite and ferrite was found at high temperatures using analytical electron microscopy facilities.« less
  • Tests were conducted on three recently developed deep-hardenable grade titanium alloys in order to assess their crack propagation and stress corrosion behavior. The alloy compositions are as follows: Alloy no. 334 (Ti-10Mo-6Cr-2.5Al); alloy no. 227 (Ti-7Mo-4Cr-2.5Al); and Alloy no. 253 (Ti-10Mo-8V-2.5Al). Compact tension specimens were cut from 6-inch diameter forging billets in three orientations. Each orientation was subsequently tested for fatigue crack growth rate and stress corrosion susceptibility. While all three alloys exhibited similar fatigue crack propagation characteristics, the chromium containing alloys appeared to be more susceptible to stress corrosion cracking. Scanning electron microscopy of the fracture surfaces revealed themore » presence of an apparently brittle rod-like phase. While the composition of the rods could not be directly determined, indirect evidence indicated that the rods were titanium borides. These rods were judged to have a significant effect on the fracture toughness and a lesser effect on the crack propagation properties of the alloys. (GRA)« less
  • The equilibrium ..gamma..-..beta.. transformation was observed at 738 +- 2/sup 0/C for both heating and cooling at the equilibrium 0.001/sup 0/C/s rate. 630 +- 10/sup 0/C was judged to be the equilibrium ..beta..-..cap alpha.. eutectoid isotherm. 5 figures. (DLC)