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Updated: May 31, 2026
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Atom Probe Tomography Analysis of Exsolved Mineral Phases
Published on: October 25, 2019
Interplay between α(Ti) nucleation and growth during peritectic solidification investigated by phase-field
J Eiken1, M Apel, V T Witusiewicz
1Access e.V., RWTH-Aachen, Intzestraße 5, 52072 Aachen, Germany.
Summary
The study reveals that controlling nucleation undercooling is key to refining the grain structure of titanium-aluminum (TiAl) alloys. Adding boron to form TiB2 particles effectively promotes nucleation, leading to significantly smaller α(Ti) grains.
Area of Science:
- Materials Science
- Metallurgy
- Computational Materials Science
Background:
- The properties of TiAl-based alloys are strongly influenced by their solidified α(Ti) grain structure.
- A coarse grain structure is typically observed when α(Ti) forms via the peritectic reaction.
Purpose of the Study:
- To investigate the formation of grain structure during early peritectic growth in TiAl alloys.
- To explore methods for refining the α(Ti) grain size through controlled nucleation.
Main Methods:
- Phase-field simulations were employed to model grain structure formation under unidirectional growth.
- Scheil calculations and Bridgman experiments were used to study in situ precipitation of TiB(2) particles.
- The role of nucleation undercooling and alloy composition was analyzed.
Main Results:
- Without foreign nucleation sites, α(Ti) nucleates on the β(Ti) phase, resulting in coarse, elongated grains for typical nucleation undercooling values.
- Reduced critical undercooling, influenced by alloy composition, can lead to grain refinement through frequent nucleation.
- In situ precipitated TiB(2) particles, controlled by boron addition, were confirmed as effective nucleation agents.
Conclusions:
- Effective grain refinement in TiAl alloys is achievable by reducing critical nucleation undercooling below the local growth undercooling.
- TiB(2) particles, formed via controlled boron addition, significantly reduce α(Ti) grain size, acting as potent nucleation agents.
- The interplay between nucleation and growth dynamics is crucial for controlling the final microstructure of TiAl alloys.
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