Diffusion bonding associated with phase transformation in (γ + β) micro-duplex titanium aluminides

N. Masahashi, S. Hanada, Y. Mizuhara

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Microstructure and bonding strength of diffusion-bonded γ titanium aluminide alloys have been investigated focusing on phase transformation during diffusion bonding. High resolution scanning electron microscopy (SEM) observation revealed that lamellar grains are evolved near a jointed interface in (γ + β) micro-duplex alloys bonded at high temperatures, while not alloys bonded at low temperatures. This result is consistent with the proposed TTT diagram with the a lamellar nose. The transformation accompanied by the redistribution of Cr is evidenced by calculating Cr composition in each phase. Lamellar structure is also observed at a localized region in the (γ + β) micro-duplex ternary alloy bonded at high temperatures. It is speculated that this region is exposed to a stress high enough to accelerate the transformation, thereby shifting the lamellar nose to shorter time or lower temperature in the TTT diagram. The phase transformation in the (γ + β) micro-duplex ter nary alloy is due to the low thermal stability of the β phase, enhancing atomic mass transport by Cr redistribution. Mechanical test revealed the high bonding strength in (γ + β) micro-duplex alloys, in which fracture was characterized by rugged fractography across lamellar boundaries in fracture surface. Thin layer is produced at the jointed interface uniformly in the micro-duplex alloy and inhomogeneously in the other two samples.

Original languageEnglish
Pages (from-to)1028-1034
Number of pages7
JournalMaterials Transactions
Volume42
Issue number6
DOIs
Publication statusPublished - 2001 Jan 1

Keywords

  • Bonding strength
  • Diffusion bonding
  • Grain boundary
  • Intermetallic compound
  • Phase stability
  • Phase transformation
  • Superplasticity

ASJC Scopus subject areas

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

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