Influence of Initiation Site and Lamellar Divergency on the Overall Kinetics of Cellular Growth and Coarsening in Aged U-Nb Alloys

Robert E. Hackenberg; Megan G. Emigh; Pallas A. Papin; Ann M. Kelly; Robert T. Forsyth; Tim J. Tucker; Kester D. Clarke

doi:10.4028/www.scientific.net/MSF.941.863

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HomeMaterials Science ForumMaterials Science Forum Vol. 941Influence of Initiation Site and Lamellar...

Influence of Initiation Site and Lamellar Divergency on the Overall Kinetics of Cellular Growth and Coarsening in Aged U-Nb Alloys

Abstract:

Overall kinetics of lamellar overaging reactions in U-5.5Nb and U-7.5Nb were analyzed by Avrami-Arrhenius analyses of volume fractions measured from an extensive temperature-time (T-t) matrix of specimens. The cellular initiation site (grain boundaries, inclusions) and regimes of lamellar divergency-cum-slowing growth rate were explicitly accounted for. Avrami exponents n from T-t regimes of constant-growth rate were consistent with theory (1<n<3); those from divergent T-t regimes were smaller, n~0.7, which is not surprising given their different growth rate behavior. The apparent activation energies Q were similar for grain-boundary and inclusion-nucleated discontinuous precipitation, indicating that their nucleation site does not alter their overall kinetics. Avrami Analysis of Isothermal Aging Kinetics

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Periodical:

Materials Science Forum (Volume 941)

Pages:

863-868

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.941.863

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Online since:

December 2018

Authors:

Robert E. Hackenberg*, Megan G. Emigh, Pallas A. Papin, Ann M. Kelly, Robert T. Forsyth, Tim J. Tucker, Kester D. Clarke

Keywords:

Aging, Discontinuous Precipitation, Growth, Nucleation, Phase Transformation

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References

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