Microstructure and mechanical properties of the intermetallic alloy Ti-45Al-6(Nb, Mo)-0.2B
The microstructure and tensile properties of the intermetallic γ-TiAl + α 2 -Ti 3 Al alloy Ti-45Al-6(Nb, Mo)-0.2B are studied after various heat and thermomechanical treatments. Its cast state is found to be characterized by a homogeneous, relatively fine-grained structure in the cases of both a mod...
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Veröffentlicht in: | Physics of metals and metallography 2008-12, Vol.106 (6), p.641-648 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The microstructure and tensile properties of the intermetallic γ-TiAl + α
2
-Ti
3
Al alloy Ti-45Al-6(Nb, Mo)-0.2B are studied after various heat and thermomechanical treatments. Its cast state is found to be characterized by a homogeneous, relatively fine-grained structure in the cases of both a model 30-g ingot and a bulk laboratory ∅120 × 180-mm ingot. The cast material subjected to heat treatment with furnace cooling and aging at
T
= 1100°C exhibits strength properties at
T
= 20–900°C that are relatively high for cast γ + α
2
alloys. Due to the rational choice of the alloy, its thermomechanical treatment is facilitated, a fine-grained structure can easily be formed upon hot deformation, and a superplastic state with elongations in the test-temperature range
T
= 900–1000°C that are very large for γ + α
2
alloys is reached. However, the high contents of niobium and molybdenum in the Ti-45Al-6(Nb, Mo)-0.2B alloy hinder the formation of an equilibrium lamellar structure upon heat treatment, and an increase in the aging temperature to
T
= 1100°C leads to the development of the α
2
→ ß(
B
2) phase transformation, which makes it impossible to reach a high level of the mechanical properties in the temperature range of the potential application of γ + α
2
alloys. Our study has revealed that the compositions of the γ + α
2
alloys need further optimization of the way of refining the niobium and molybdenum contents. |
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ISSN: | 0031-918X 1555-6190 |
DOI: | 10.1134/S0031918X08120132 |