Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Liquid Penetration and Particle Separation during the Initial Stage of Liquid Phase Sintering
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.ORCID iD: 0000-0003-0864-3679
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2006 (English)In: Metallurgical transactions. A, ISSN 0360-2133Article in journal (Refereed) In press
Place, publisher, year, edition, pages
2006.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-5450OAI: oai:DiVA.org:kth-5450DiVA: diva2:9816
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
In thesis
1. Liquid phase sintering of W-Ni-Fe composites: liquid penetration, agglomerate separation and tungsten particle growth
Open this publication in new window or tab >>Liquid phase sintering of W-Ni-Fe composites: liquid penetration, agglomerate separation and tungsten particle growth
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The initial stage of liquid phase sintering, involving liquid penetration, agglomerate separation, particle spreading and growth has been investigated in experiments using tungsten heavy alloys. The particle composites used were produced by hot isostatic pressing (HIP) of pure powder mixtures of W-Ni-Fe-(Co). By using different HIP temperatures, volume fractions of tungsten, alloying elements like Cobalt and Sulphur or excluding Iron from the matrix, liquid penetration, agglomerate separation and particle growth conditions were affected. The investigations were performed mainly under microgravity (sounding rockets or parabolic trajectories by airplanes) but at high tungsten particle fractions, short sintering times or at infiltration of solid pure tungsten, they were performed at normal gravity. The liquid penetration of the tungsten agglomerates is explained by initial wetting under non-equilibrium conditions, due to the reaction between the liquid matrix and the particles, and a decrease of interfacial energy. The dissolving of tungsten gives a pressure drop in the penetrating liquid and a driving force for the liquid movement by a suggested parabolic penetration model. For cold worked tungsten, a penetration theory was proposed, where an internal stress release in the penetrated tungsten grains creates space for the advancing liquid.

The spreading of the tungsten agglomerates is explained by an interagglomerate melt swelling due to a Kirkendall effect. The liquid matrix undergoes a volume increase since the diffusion rates of Ni-Fe are higher than for W and initial concentration gradients of W and Ni, Fe exists. The suggested model by Kirkendall are also used for an analysis of the interaction behaviour between solid particles and a solidification front and inclusion behaviour in iron base alloys during teeming and deoxidation.

The average tungsten particles size decrease initially since part of the tungsten particles is dissolved when the non-equilibrium matrix phase is melting. When equilibrium is reached, the tungsten particles grow in accordance with the Ostwald ripening process by an approximately 1/3 power law. Larger particle fraction of particles showed a higher growth rate, due to shorter diffusion distances between the particles. Cobalt, Sulphur and absence of iron in the matrix were found to increase the growth rate of the tungsten particles due to a higher surface tension between the solid tungsten particles and the matrix melt.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006
Series
Trita-MG, ISSN 1104-7127 ; 2006:1
Keyword
Liquid phase sintering, heavy metal, particle composites, tungsten, penetration, agglomerate separation, particle interaction, parabolic flight, sounding rockets, microgravity, Kirkendall effect
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-3870 (URN)
Public defence
2006-03-22, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved

Open Access in DiVA

No full text

Authority records BETA

Eliasson, Anders

Search in DiVA

By author/editor
Eliasson, AndersEkbom, Lars BFredriksson, Hasse
By organisation
CeramicsMaterials Science and Engineering
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 58 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf