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Influence of upset forging and heat treatment on the microstructure and mechanical properties of a new β-solidifying γ-TiAl alloy
Our previous works revealed that alloying of a β-solidifying intermetallic γ-TiAl alloy with Zr and Hf instead of Nb led to improvement in the strength and creep resistance due to effective solid solution hardening, a strong partitioning preference γ>α2 for Zr and a lower lattice misfit of the γ-...
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Published in: | Intermetallics 2023-12, Vol.163, p.108078, Article 108078 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Our previous works revealed that alloying of a β-solidifying intermetallic γ-TiAl alloy with Zr and Hf instead of Nb led to improvement in the strength and creep resistance due to effective solid solution hardening, a strong partitioning preference γ>α2 for Zr and a lower lattice misfit of the γ-TiAl and α2-Ti3Al phases. On this basis, a new β-solidifying γ-TiAl alloy with a composition Ti-44Al-X(Nb,Zr,Hf)-0.15B (at.%) (designated as TNZ γ-alloy) has been designed. The as-cast ingot had a fine lamellar structure with a small amount of the metastable β(βo) phase. Compression tests performed at T = 950–1200 °C showed that the new alloy possessed good forgeability even at 950 °C without signs of strain localization. The alloy ingot was subjected to upset forging at T = 950 °C followed by heat treatments. The applied processing led to formation of refined duplex and lamellar type structures almost free of the β(βo) phase. The obtained microstructural conditions were examined and then the tensile and creep tests were performed. The mechanical tests showed that with increasing the lamellar constituent and decreasing the lamellar spacing the creep resistance expectedly increased and ductility decreased. The obtained results are discussed from the viewpoint of processability, mechanical properties and oxidation resistance of the new alloy.
•A new β-solidifying γ-TiAl alloy doped with Nb, Zr and Hf was investigated.•Upset forging at 950 °C did not lead to strain localization and flow instabilities.•Various microstructural conditions were obtained by upsetting and heat treatment.•The onset of the brittle-ductile transition in the alloy occurred at T ≥ 850 °C.•The new alloy exhibited a good balance of tensile and creep properties. |
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ISSN: | 0966-9795 1879-0216 |
DOI: | 10.1016/j.intermet.2023.108078 |