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 language | English |
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Pages (from-to) | 1028-1034 |
Number of pages | 7 |
Journal | Materials Transactions |
Volume | 42 |
Issue number | 6 |
DOIs | |
Publication status | Published - 2001 |
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