Phase relations in concentrated Ta-Hf and Nb-Hf alloys

Ray Carpenter, C. T. Liu, P. G. Mardon

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The precipitation reactions occurring in concentrated Ta-Hf and Nb-Hf alloys over the temperature range 600° to 1400°C were investigated by X-ray diffraction and transmission microscopy. In Ta-Hf alloys containing 30 to 62 at. pct Hf and Nb-Hf alloys containing 25 to 50 at. pct Hf a stable bcc solid solution exists at elevated temperature. When quenched from the single phase region and aged at lower temperatures both alloys precipitate α phase, an hcp hafnium-rich phase. Transmission microscopy showed that in the Nb-Hf system the precipitation reaction begins with the formation of coherent zones. Further aging causes coarsening into discs, still at least partially coherent. When coherency is lost the α morphology changes to rod-type. The effect of small amounts of oxygen added to these alloys during aging is an increase in the unit cell size of the α phase. Oxygen concentrations up to ~0.5 at. pct do not cause observable changes in the phase relations. These results cannot be reconciled with the miscibility gap-monotectoid type phase diagrams reported by some earlier investigators and indicate that the proper phase diagram for both systems is the β-isomorphous type.

Original languageEnglish (US)
Pages (from-to)125-131
Number of pages7
JournalMetallurgical Transactions
Volume2
Issue number1
DOIs
StatePublished - Dec 1971
Externally publishedYes

Fingerprint

Phase diagrams
Microscopic examination
Hafnium
Aging of materials
phase diagrams
Oxygen
microscopy
miscibility gap
causes
hafnium
Coarsening
oxygen
Temperature
Precipitates
precipitates
Solid solutions
solid solutions
rods
Solubility
X ray diffraction

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Metals and Alloys
  • Materials Chemistry
  • Mechanics of Materials
  • Engineering(all)

Cite this

Phase relations in concentrated Ta-Hf and Nb-Hf alloys. / Carpenter, Ray; Liu, C. T.; Mardon, P. G.

In: Metallurgical Transactions, Vol. 2, No. 1, 12.1971, p. 125-131.

Research output: Contribution to journalArticle

Carpenter, Ray ; Liu, C. T. ; Mardon, P. G. / Phase relations in concentrated Ta-Hf and Nb-Hf alloys. In: Metallurgical Transactions. 1971 ; Vol. 2, No. 1. pp. 125-131.
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