Grain refining and superplastic compaction of rapidly solidified TiAl powder with phase separation of nonequilibrium α2 martensite

Minoru Nishida, Y. Morizono, T. Kai, J. Sugimoto, A. Chiba

Research output: Contribution to journalArticle

Abstract

There were two kinds of powders with respect to microstructures in the rapidly solidified Ti-rich TiAl powders produced by Plasma Rotating Electrode Process (PREP). The first one had a surface relief of a martensitic phase and consisted of α2 lath plates and the primary phase during solidification was deduced to be the β phase, which is referred as M powder. The second one had a dendritic structure and consisted of α2/γ lamellar and γ phases decomposed in the α2 matrix, which is referred as D powder. The primary phase of the D powder during solidification was determined to be the α phase. In Ti-40 at%Al alloy, α2/γ lamellar and α2/γ microduplex structures were formed in D and M powders, respectively, by annealing at 1273 K. The microduplex structure consisted of γ precipitate in α2 matrix with the usual orientation relationship. The D powder was difficult to compact by hot press at 1273 K at 50 MPa. Lots of dislocations were observed in the lamellar structure. The M powder was compacted easily by hot press at 1273 K at 50 MPa. α2 and γ phases in the duplex structure were lost the usual orientation relationship during the hot press. There were no dislocations inside of α2 and γ crystal grains. It was concluded that the grain boundary sliding was a predominant deformation mode in the M powder during the hot press. In other words, the M powder exhibited a superplastic deformation behavior at elevated temperature. D and M powders in Ti-45 and 47 at%Al alloys showed the same tendency as those in Ti-40 at%Al alloy.

Original languageEnglish
Pages (from-to)303-310
Number of pages8
JournalMaterials Science Forum
Volume233-234
Publication statusPublished - Dec 1 1997
Externally publishedYes

Fingerprint

refining
martensite
Martensite
Phase separation
Powders
Refining
Compaction
solidification
Solidification
rotating plasmas
Superplastic deformation
Grain boundary sliding
Lamellar structures
matrices
Dislocations (crystals)
sliding
Precipitates
precipitates
tendencies
grain boundaries

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Grain refining and superplastic compaction of rapidly solidified TiAl powder with phase separation of nonequilibrium α2 martensite. / Nishida, Minoru; Morizono, Y.; Kai, T.; Sugimoto, J.; Chiba, A.

In: Materials Science Forum, Vol. 233-234, 01.12.1997, p. 303-310.

Research output: Contribution to journalArticle

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