Abstract
In this study a two-step heat treatment was applied to high Nb containing γ-TiAl based alloys in order to investigate the initial stage of the lamellae formation in ordered (α2-grains as well as in massively transformed γm-grains. The first heat treatment step, conducted in the single a-phase field followed by oil quenching, leads to a microstructure consisting of supersaturated engrains and a small volume fraction of γm-grains. The second step of the heat treatment was performed below the eutectoid temperature, i.e. within the ((α 2+γ)-phase field region and was again followed by oil quenching. There, the formation of ultra-fine γ-lamellae takes place in the (α2-grains and (some) fine (α2-lamellae are formed in the αm-grains. In both cases the lamellae show a Blackburn orientation relationship with the matrix grain. It was found that the precipitation of γ-laths in the supersaturated (α2-grains is faster than the formation of (α2-laths in γm-grains. The characteristics of the initial stage of formation were investigated by transmission electron microscopy.
| Original language | English |
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| Pages (from-to) | 153-158 |
| Number of pages | 6 |
| Journal | Materials Research Society Symposium Proceedings |
| Volume | 1128 |
| State | Published - 2009 |
| Externally published | Yes |
| Event | 2008 MRS Fall Meeting - Boston, MA, United States Duration: 2 Dec 2008 → 4 Dec 2008 |