Laser weld geometry and microstructure of cast Uranium-6 wt% niobium alloy

J. W. Elmer, A. S. Wu, Tarasankar Debroy

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Laser welding was performed on a U6wt%Nb uranium alloy using a 400 W solid state laser with welding speeds from 20 to 2500 mm/s. This speed range spanned melt pool sizes from traditional welding to surface modification and additive manufacturing. With increasing scan speed, the ratio of weld length relative to depth and width increased, with melt pool lengths being more than 5x greater than the width and 10x greater than the depth at the highest speeds. Keyhole mode welds were shown to occur at low speeds, while conduction mode welds occurred at 700 mm/s or higher as the weld depth dropped off more rapidly than width at higher speeds. Microstructures that form at the boundary between the fusion zone and base metal were observed to have a nonconventional appearance consisting of interpenetrating dark and light contrast phases before cells or dendrites appear. Dendrites with secondary arms form from this boundary in keyhole welds and refine to no visible secondary arms near the weld center. Primary and secondary dendrite arms, where present, were shown to refine in size inversely with cooling rate raised to the 0.465 and 0.375 powers respectively. Dendrites were largely absent from the conduction mode welds at higher speeds, and were replaced by a banded microstructure that appears to form by an oscillatory solidification front mechanism.

Original languageEnglish (US)
Pages (from-to)224-237
Number of pages14
JournalJournal of Nuclear Materials
Volume514
DOIs
StatePublished - Feb 1 2019

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niobium alloys
Niobium alloys
Uranium
dendrites
uranium
casts
Welds
microstructure
Microstructure
Geometry
Lasers
high speed
geometry
welding
lasers
uranium alloys
conduction
laser welding
phase contrast
solid state lasers

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Materials Science(all)
  • Nuclear Energy and Engineering

Cite this

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abstract = "Laser welding was performed on a U6wt{\%}Nb uranium alloy using a 400 W solid state laser with welding speeds from 20 to 2500 mm/s. This speed range spanned melt pool sizes from traditional welding to surface modification and additive manufacturing. With increasing scan speed, the ratio of weld length relative to depth and width increased, with melt pool lengths being more than 5x greater than the width and 10x greater than the depth at the highest speeds. Keyhole mode welds were shown to occur at low speeds, while conduction mode welds occurred at 700 mm/s or higher as the weld depth dropped off more rapidly than width at higher speeds. Microstructures that form at the boundary between the fusion zone and base metal were observed to have a nonconventional appearance consisting of interpenetrating dark and light contrast phases before cells or dendrites appear. Dendrites with secondary arms form from this boundary in keyhole welds and refine to no visible secondary arms near the weld center. Primary and secondary dendrite arms, where present, were shown to refine in size inversely with cooling rate raised to the 0.465 and 0.375 powers respectively. Dendrites were largely absent from the conduction mode welds at higher speeds, and were replaced by a banded microstructure that appears to form by an oscillatory solidification front mechanism.",
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Laser weld geometry and microstructure of cast Uranium-6 wt% niobium alloy. / Elmer, J. W.; Wu, A. S.; Debroy, Tarasankar.

In: Journal of Nuclear Materials, Vol. 514, 01.02.2019, p. 224-237.

Research output: Contribution to journalArticle

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AB - Laser welding was performed on a U6wt%Nb uranium alloy using a 400 W solid state laser with welding speeds from 20 to 2500 mm/s. This speed range spanned melt pool sizes from traditional welding to surface modification and additive manufacturing. With increasing scan speed, the ratio of weld length relative to depth and width increased, with melt pool lengths being more than 5x greater than the width and 10x greater than the depth at the highest speeds. Keyhole mode welds were shown to occur at low speeds, while conduction mode welds occurred at 700 mm/s or higher as the weld depth dropped off more rapidly than width at higher speeds. Microstructures that form at the boundary between the fusion zone and base metal were observed to have a nonconventional appearance consisting of interpenetrating dark and light contrast phases before cells or dendrites appear. Dendrites with secondary arms form from this boundary in keyhole welds and refine to no visible secondary arms near the weld center. Primary and secondary dendrite arms, where present, were shown to refine in size inversely with cooling rate raised to the 0.465 and 0.375 powers respectively. Dendrites were largely absent from the conduction mode welds at higher speeds, and were replaced by a banded microstructure that appears to form by an oscillatory solidification front mechanism.

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