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Formation of columnar lamellar colony grain structure in a high Nb-TiAl alloy by electron beam melting

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journal contribution
posted on 25.03.2020 by W. Kan, B. Chen, H. Peng, Y. Liang, J. Lin
The grain morphology and texture control in electron beam melted (EBM) Ti-47Al-8Nb γ-TiAl alloy is considered. The EBM process window to obtain a columnar lamellar colony (CLC) grain structure was defined following a critical assessment of thermal gradient and liquid-solid interface velocity by using numerical simulation. Experimentally, an epitaxial grain growth during solidification of Ti-47Al-8Nb has been realised by using the optimum EBM parameter sets. The length of the CLC grain structure reached up to ∼600 μm (compared to the powder layer thickness of 70 μm). The texture analysis and phase identification performed using electron backscatter diffraction (EBSD) provided important insights in understanding the solidification and phase transformation processes during the EBM fabrication. It was found that the solidification path for EBM high Nb-TiAl alloy involves the high-temperature α-phase field (i.e. L+β→α and α→α2+γ phase transformation processes). The epitaxial growth of prior β grains and the anchoring effect of residual B2-phase are very likely to be responsible for the formation of CLC microstructure.

History

Citation

Journal of Alloys and Compounds 809 (2019) 151673

Author affiliation

Department of Engineering

Version

AM (Accepted Manuscript)

Published in

Journal of Alloys and Compounds

Volume

809

Publisher

ELSEVIER SCIENCE SA

issn

0925-8388

eissn

1873-4669

Acceptance date

01/08/2019

Copyright date

2019

Available date

02/08/2019

Publisher version

https://www.sciencedirect.com/science/article/pii/S0925838819329068

Language

English

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