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Title: Low-Temperature Aging Mechanisms in U-6wt% Nb

Abstract

Phase stability and aging mechanisms in a water-quenched (WQ) U-6wt% Nb (U-14at% Nb) alloy artificially aged at 200 C and naturally aged at ambient temperature for 15 years have been investigated and studied using Vickers-hardness measurement, X-ray diffraction (XRD) analysis, and transmission electron microscopy (TEM) techniques. Age hardening/softening phenomenon is recorded from the artificially aged samples based upon the microhardness measurement. The age hardening can be readily rationalized by the occurrence of fine-scaled Nb segregation, or spinodal decomposition, within the {alpha}'' domains, which results in the formation of a modulated structure containing nano-scaled Nb-rich and Nb-lean domains. Prolonged aging leads to age softening of the alloy by coarsening of the modulated structure. Chemical ordering, or disorder-order phase transformation, is found within the naturally aged alloy according to TEM observations of antiphase domain boundaries (APBs) and superlattice diffraction patterns. A possible superlattice structure for the ordered {alpha}'' phase observed in the naturally aged sample and underlying low-temperature aging mechanisms are proposed.

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15011604
Report Number(s):
UCRL-TR-208589
TRN: US200507%%487
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 7 Dec 2004
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AGE HARDENING; AGING; ALLOYS; AMBIENT TEMPERATURE; DIFFRACTION; MICROHARDNESS; PHASE STABILITY; PHASE TRANSFORMATIONS; SEGREGATION; SUPERLATTICES; TRANSMISSION ELECTRON MICROSCOPY; VICKERS HARDNESS; X-RAY DIFFRACTION

Citation Formats

Hsiung, L L. Low-Temperature Aging Mechanisms in U-6wt% Nb. United States: N. p., 2004. Web. doi:10.2172/15011604.
Hsiung, L L. Low-Temperature Aging Mechanisms in U-6wt% Nb. United States. https://doi.org/10.2172/15011604
Hsiung, L L. 2004. "Low-Temperature Aging Mechanisms in U-6wt% Nb". United States. https://doi.org/10.2172/15011604. https://www.osti.gov/servlets/purl/15011604.
@article{osti_15011604,
title = {Low-Temperature Aging Mechanisms in U-6wt% Nb},
author = {Hsiung, L L},
abstractNote = {Phase stability and aging mechanisms in a water-quenched (WQ) U-6wt% Nb (U-14at% Nb) alloy artificially aged at 200 C and naturally aged at ambient temperature for 15 years have been investigated and studied using Vickers-hardness measurement, X-ray diffraction (XRD) analysis, and transmission electron microscopy (TEM) techniques. Age hardening/softening phenomenon is recorded from the artificially aged samples based upon the microhardness measurement. The age hardening can be readily rationalized by the occurrence of fine-scaled Nb segregation, or spinodal decomposition, within the {alpha}'' domains, which results in the formation of a modulated structure containing nano-scaled Nb-rich and Nb-lean domains. Prolonged aging leads to age softening of the alloy by coarsening of the modulated structure. Chemical ordering, or disorder-order phase transformation, is found within the naturally aged alloy according to TEM observations of antiphase domain boundaries (APBs) and superlattice diffraction patterns. A possible superlattice structure for the ordered {alpha}'' phase observed in the naturally aged sample and underlying low-temperature aging mechanisms are proposed.},
doi = {10.2172/15011604},
url = {https://www.osti.gov/biblio/15011604}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 07 00:00:00 EST 2004},
month = {Tue Dec 07 00:00:00 EST 2004}
}