Property and lifetime prediction in aged U-Nb alloys: a statistical assessment

PDF Version Also Available for Download.

Description

This study was undertaken to better model the aging response of U-Nb alloys, particularly to predict properties and their scatter bands, from which lifetimes and their uncertainties can be evaluated. Predictive models of the aging time- and temperature-dependencies of seven age-sensitive properties were developed for nonbanded U-5.6 wt% Nb and U-7.7 wt% Nb alloys. These properties were total and uniform plastic tensile elongation to failure; first-yield, second-yield, and ultimate tensile strengths; first-yield elastic modulus; and Vickers microhardness. A more systematic and statistically aware kinetics modeling approach than employed previously gave reasonable models fits to accelerated aging property data in nonbanded ... continued below

Physical Description

743 KB

Creation Information

Hackenberg, Robert E. & Hemphill, Geralyn M. February 1, 2009.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

This study was undertaken to better model the aging response of U-Nb alloys, particularly to predict properties and their scatter bands, from which lifetimes and their uncertainties can be evaluated. Predictive models of the aging time- and temperature-dependencies of seven age-sensitive properties were developed for nonbanded U-5.6 wt% Nb and U-7.7 wt% Nb alloys. These properties were total and uniform plastic tensile elongation to failure; first-yield, second-yield, and ultimate tensile strengths; first-yield elastic modulus; and Vickers microhardness. A more systematic and statistically aware kinetics modeling approach than employed previously gave reasonable models fits to accelerated aging property data in nonbanded U-5.6Nb and U-7.7Nb, and useful predictions for most of the properties studied. With minor modifications, the U-5.6Nb model was extended to banded U-6Nb. This modeling approach shared many of the key assumptions of the previous approach, including the assumption of Arrhenius behavior and the use of three adjustable parameters. Initial data returns from long-term aging experiments were used to validate the fitted models, a new feature to this study. The apparent activation energies of aging for the property of greatest interest, total elongation, were 32 kcal/mol for U-5.6Nb and 39 kcal/mol for U-7.7Nb, respectively; those for the other properties spanned 14–51 kcal/mol. Comparing the goodness of the model fits for the seven properties, the best fits were obtained for second-yield strength and hardness, the first-yield modulus fit the least well, and the other properties’ fits were in between. The U-5.6Nb models are more robust and therefore are expected to have better predictive power than those of U-7.7Nb, especially at the lower aging temperatures of interest. Model extrapolations to longer times (up to 5 years) and lower temperatures (as low as 40ºC) than those used for the model fitting agreed well with most of the validation data gathered for both nonbanded alloys, as well as banded U-6Nb, giving provisional validation of the fitted models. Property predictions for planned or already pending validation experiments are also provided. With a view towards enabling future modeling efforts, this report tabulates all replicate tensile properties and complete hardness scan data used for both model fitting and validation. For surveillance purposes, the properties most practically amenable to detecting the onset of aging at the earliest times are first-yield strength and second-yield strength. Even at aging temperatures as high as 60ºC, the minimum lifetimes from this present study are beyond 100 years, giving no cause for concern, if the previously developed failure criterion based on uniaxial tensile elongation (with its caveats) is accepted.

Physical Description

743 KB

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: LA-14389
  • Grant Number: DE-AC52-06NA25396
  • DOI: 10.2172/957046 | External Link
  • Office of Scientific & Technical Information Report Number: 957046
  • Archival Resource Key: ark:/67531/metadc932444

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • February 1, 2009

Added to The UNT Digital Library

  • Nov. 13, 2016, 7:26 p.m.

Description Last Updated

  • Feb. 2, 2018, 12:03 p.m.

Usage Statistics

When was this report last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 1

Interact With This Report

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

International Image Interoperability Framework

IIF Logo

We support the IIIF Presentation API

Hackenberg, Robert E. & Hemphill, Geralyn M. Property and lifetime prediction in aged U-Nb alloys: a statistical assessment, report, February 1, 2009; Los Alamos, New Mexico. (digital.library.unt.edu/ark:/67531/metadc932444/: accessed September 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.