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Microstructure and mechanical properties of a high Nb-TiAl alloy fabricated by electron beam melting

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posted on 2019-06-14, 14:10 authored by B Chen, W Kan, C Jing, H Peng, J Lin
Electron beam melting (EBM) has been applied to fabricate a high Nb-TiAl alloy with a fully dense microstructure and good tensile properties at both room and high temperatures. The effects of preheating and melting parameters on melting, solidification, phase transformation and resulting microstructure formation in as-EBM high Nb-TiAl alloy were investigated by performing a design-of-experiments. Results show that the limited EBM processing window can be broadened to produce different characteristic microstructures ranging from nearly fully lamellar γ/α2 to equiaxed γ grains. Such a broadened processing window has been achieved by using stronger preheating beam current. A numerical simulation was performed to understand temperature evolution at a fixed point of interest where electron beam passed several times with a certain line offset within one build layer. Both the preheating and melting stages were considered in the model. Modelling results show that a higher preheating beam current resulted in a longer hold time within the temperature range between 1300 and 1380 °C (i.e. single α-phase region). This helped to produce fine lamellar microstructure in the high Nb-TiAl alloy. Fundamental principles are thus proposed in terms of controlling microstructure formation and fabricating fully dense high Nb-TiAl alloy in as-EBM condition.

Funding

The work was supported by the National Natural Science Foundation of China (No. 51831001 and No. 51671016) and the State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing (2017-ZD03). Bo Chen acknowledges UK's Engineering and Physical Sciences Research Council, EPSRC, for financial support through the First Grant Scheme EP/P025978/1 to facilitate the international research collaboration. Part of this work was done during the time period when Beihang University provided Bo Chen additional financial support through the Visiting Associate Professorship scheme 2016 and 2017. Bo Chen is grateful to Prof. Shengkai Gong at Beihang University, for providing these awards.

History

Citation

Materials and Design, 2018, 160, pp. 611-623

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Engineering

Version

  • VoR (Version of Record)

Published in

Materials and Design

Publisher

Elsevier

issn

0264-1275

Acceptance date

2018-09-26

Copyright date

2018

Available date

2019-06-14

Publisher version

https://www.sciencedirect.com/science/article/pii/S0264127518307469?via=ihub

Notes

Supplementary data to this article can be found online at https://doi.org/10.1016/j.matdes.2018.09.044.

Language

en

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