Details

Autor(en) / Beteiligte

• Song, L.
• Xu, X.J.
• You, L.
• Liang, Y.F.
• Lin, J.P.

Titel

Phase transformation and decomposition mechanisms of the βo(ω) phase in cast high Nb containing TiAl alloy

Ist Teil von

• Journal of alloys and compounds, 2014-12, Vol.616, p.483-491

Ort / Verlag

Kidlington: Elsevier B.V

Erscheinungsjahr

2014

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •The phase transformation process in the Nb-segregation area is studied.•The ωo phase undergoes B82-ωo→D88-ω→γ transformation during annealing.•The βo(ω)→γ transformation can be realized in several ways.•The ωo particles act as pinning points during the βo(ω)→γ transformation. High Nb containing TiAl (Nb–TiAl) alloys are thought to be used at higher temperatures than the conventional TiAl alloys, typically up to 900°C. However, the βo and ω-related phases are usually induced by Nb-segregation in cast alloys. It is important to reveal the transformation mechanisms of the βo and ω-related phases at elevated temperatures for better design of the alloy and optimizing the heat treatment process. In this study, the interconversion mechanism between the ordered ω and βo phases and the decomposition process of the βo phase in the as-cast Ti–45Al–8.5Nb–0.2W–0.2B–0.02Y (at.%) alloy are studied. The ωo particles grow up by richening Nb and rejecting W to the surrounding βo matrix. The βo and ωo phase are separated after annealing at 900°C, whereas the ωo phase dissolves into the βo matrix after annealing at 950°C. The βo and ωo phases undergo βo→γ and ωo (B82 structure)→D88-ω (D88 structure)→γ transformation respectively during annealing, and the βo→γ transformation can be achieved in several ways. The ωo particles with a high Nb content act as pinning points at the βo/γ boundaries during the βo→γ transformation. The corresponding mechanisms of the transformations mentioned above are discussed.