skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Kinetics of cellular transformation and competing precipitation mechanisms during sub-eutectoid annealing of U10Mo alloys

Abstract

Transformation kinetics of metastable body-centered cubic γ-UMo phase in U-10 wt.percent Mo alloy during annealing at sub-eutectoid temperatures of 500C and 400C has been determined as a function of time using detailed microstructural characterization by scanning electron microscopy, X-ray diffraction analysis, scanning transmission electron microscopy, and atom probe tomography. Based on the results, we found that the phase transformation is initiated by cellular transformation at both the temperatures, which results in formation of a lamellar microstructure along prior γ-UMo grain boundaries.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1371976
Report Number(s):
PNNL-SA-124502
Journal ID: ISSN 0925-8388; 50080; DN2006000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Alloys and Compounds; Journal Volume: 723; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Environmental Molecular Sciences Laboratory

Citation Formats

Jana, S., Devaraj, A., Kovarik, L., Arey, B., Sweet, L., Varga, T., Lavender, C., and Joshi, V.. Kinetics of cellular transformation and competing precipitation mechanisms during sub-eutectoid annealing of U10Mo alloys. United States: N. p., 2017. Web. doi:10.1016/j.jallcom.2017.06.292.
Copy to clipboard
Jana, S., Devaraj, A., Kovarik, L., Arey, B., Sweet, L., Varga, T., Lavender, C., & Joshi, V.. Kinetics of cellular transformation and competing precipitation mechanisms during sub-eutectoid annealing of U10Mo alloys. United States. doi:10.1016/j.jallcom.2017.06.292.
Copy to clipboard
Jana, S., Devaraj, A., Kovarik, L., Arey, B., Sweet, L., Varga, T., Lavender, C., and Joshi, V.. Wed . "Kinetics of cellular transformation and competing precipitation mechanisms during sub-eutectoid annealing of U10Mo alloys". United States. doi:10.1016/j.jallcom.2017.06.292.
Copy to clipboard
@article{osti_1371976,
title = {Kinetics of cellular transformation and competing precipitation mechanisms during sub-eutectoid annealing of U10Mo alloys},
author = {Jana, S. and Devaraj, A. and Kovarik, L. and Arey, B. and Sweet, L. and Varga, T. and Lavender, C. and Joshi, V.},
abstractNote = {Transformation kinetics of metastable body-centered cubic γ-UMo phase in U-10 wt.percent Mo alloy during annealing at sub-eutectoid temperatures of 500C and 400C has been determined as a function of time using detailed microstructural characterization by scanning electron microscopy, X-ray diffraction analysis, scanning transmission electron microscopy, and atom probe tomography. Based on the results, we found that the phase transformation is initiated by cellular transformation at both the temperatures, which results in formation of a lamellar microstructure along prior γ-UMo grain boundaries.},
doi = {10.1016/j.jallcom.2017.06.292},
journal = {Journal of Alloys and Compounds},
number = C,
volume = 723,
place = {United States},
year = {Wed Nov 01 00:00:00 EDT 2017},
month = {Wed Nov 01 00:00:00 EDT 2017}
}
Copy to clipboard
Journal Article:
DOI:  10.1016/j.jallcom.2017.06.292
Other availability
Find in Google Scholar Find in Google Scholar
Search WorldCat Search WorldCat to find libraries that may hold this journal
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • ; - Acta Materialia
    The dissolution of globular M{sub 23}C{sub 6} carbide in Fe-W-C and Fe-Mo-C steels during austenitization has been studied by means of transmission electron microscopy (TEM). It was observed that the M{sub 23}C{sub 6} carbide formed at 700 C decomposes by two different eutectoid reactions. In the early stage of dissolution, before the {alpha}{yields}{gamma} transformation is completed at austenitization temperature, the M{sub 23}C{sub 6} carbide transforms into M{sub 6}C + {alpha} with the formation of spheroidal M{sub 6}C precipitates. The first reaction takes place while the carbide is still surrounded by ferrite. After the {alpha}{yields}{gamma} transformation, the M{sub 23}C{sub 6} carbidemore » decomposes into M{sub 6}C + {gamma} in Fe-W-C steels and into Fe{sub 2}MoC + {gamma} or M{sub 6}C + {gamma} in Fe-Mo-C steels. In the latter cases a rod-like or lamellar structure was observed. It was established that phase boundary migration during M{sub 23}C{sub 6} carbide dissolution initiates the precipitation reaction at the interface. The precipitates were characterized by X-ray diffraction and by TEM-EDS. The orientation relationship between M{sub 6}C and austenite and M{sub 6}C and martensite after M{sub 2}C{sub 6} decomposition has been determined. The results obtained indicate that in both Fe-Mo-C and Fe-W-C steels, M{sub 23}C{sub 6} carbide is not stable in the temperature range of 800--1,000 C. The observed results will be discussed in terms of local equilibrium at the phase interfaces during the reactions.« less

  • ; ; ; ... - Journal of Applied Physics
    The kinetics of deuterium doping of and removal from polycrystalline (Ba,Sr)TiO{sub 3} (BST) thin films during annealing were investigated using secondary ion mass spectrometry depth profiling, and the data were correlated to changes in the electrical behavior of the films. Results for deuterium doping of exposed BST films on a Pt bottom electrode layer are consistent with incorporation of deuterium interstitial defects at the BST/Pt interface and {open_quotes}upward{close_quotes} diffusion toward the film surface. The incorporation kinetics of deuterium in Pt/BST/Pt capacitors are more complex and are greatly enhanced by the presence of the Pt top electrode. Removal of deuterium frommore » D{sub 2}/N{sub 2}-exposed Pt/BST/Pt specimens during oxygen recovery anneals appears to be limited by the rate of an interfacial reaction at low temperatures (200{endash}250{degree}C). The pre-D{sub 2} exposure leakage current properties of the BST capacitors were found to be largely recovered when the deuterium concentration in the films was reduced to {similar_to}10{sup 19}cm{sup {minus}3} during post-D{sub 2} oxygen recovery anneals. Recovery annealing in vacuum, although it removed deuterium from the films, was found to result in an increase in leakage current density for annealing temperatures greater than 300{degree}C. These results suggest that introduction of large amounts of positive space charge into the BST films has a pronounced effect on the electrical properties of the Pt/BST interface. {copyright} 2001 American Institute of Physics.« less

  • ; - Acta Materialia
    A computer simulation study has been performed of the reaction paths for the precipitation of {delta}{prime} (Al{sub 3}Li) ordered particles from a disordered matrix ({alpha}) in Al-Li alloys, using microscopic Langevin diffusion equations. It is found that the precipitation of {delta}{prime} occurs either by a congruent ordering process followed by decomposition, or by a non-classical nucleation mechanism which requires critical fluctuations of both composition and order parameter, except in a narrow range of compositions near the equilibrium phase boundary of the disordered phase, where classical nucleation theory seems to be applicable. Composition and order parameter profiles across a critical nucleusmore » were obtained for different compositions in the nucleation and growth regime, and compared with those obtained from the continuum non-classical nucleation theory. Possible origins for the discrepancies in the precipitation mechanism, obtained from different theoretical and experimental studies, are suggested.« less

  • ; ; ; ... - Scripta Materialia
    Austenitization is an inevitable occurrence during the heat treatment of steels. Despite this consideration, less attention has been paid so far to the study of the formation of austenite as compared with the vast amount of research on its decomposition. That is because the steel properties depend basically on the transformation processes following austenitization. However, the initial austenitic condition is important to the development of the final microstructure and its mechanical properties. The Avrami equation is generally used to model transformations under isothermal conditions. However, in this paper the authors present a model in which this equation has been appliedmore » successfully in the modelling of the pearlite-to-austenite transformation during continuous heating in a eutectoid steel with a fully pearlitic initial microstructure. Moreover, since dilatometric analysis is a technique very often employed to study phase transformations in steels, calculations of relative change in length have been made as function of temperature, and the differences between theoretical and experimental results have been analyzed.« less

  • ; - AIP Advances
    In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponentsmore » obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.« less