Effects of Withdrawal Rate on the Microstructure of Directionally Solidified GH4720Li Superalloys
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Beijing Central Iron and Steel Research Institute, Beijing 100081, China
2
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
3
Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing 100083, China
4
School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(5), 771; https://doi.org/10.3390/ma12050771
Received: 13 February 2019
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Revised: 1 March 2019
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Accepted: 4 March 2019
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Published: 6 March 2019
(This article belongs to the Special Issue Superalloys–Currents Trends in Development of Their Microstructure and Properties)
Increasing the ingot size of GH4720Li superalloys makes it difficult to control their microstructure, and the withdrawal rate is an important factor in controlling and refining the microstructure of GH4720Li superalloys. In this study, GH4720Li superalloy samples were prepared via Bridgman-type directional solidification with different withdrawal rates. The morphology and average size of the dendrites in the stable growth zone during directional solidification in each sample, morphology and average size of the γ’ phases, and microsegregation of each alloying element were analyzed using optical microscopy, Photoshop, Image Pro Plus, field emission scanning electron microscopy, and electron probe microanalysis. Increasing the withdrawal rate significantly helped in refining the superalloy microstructure; the average secondary dendrite arm spacing decreased from 133 to 79 µm, whereas the average sizes of the γ’ phases in the dendrite arms and the interdendritic regions decreased from 1.02 and 2.15 µm to 0.69 and 1.26 µm, respectively. Moreover, the γ’ phase distribution became more uniform. The microsegregation of Al, Ti, Cr, and Co decreased with the increase in the withdrawal rate; the segregation coefficients of Al, Cr, and Co approached 1 at higher withdrawal rates, whereas that of Ti remained above 2.2 at all the withdrawal rates.
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Keywords:
withdrawal rate; GH4720Li; microstructure; average secondary dendrite arm spacing; γ’ phase; segregation coefficient
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MDPI and ACS Style
Qu, J.; Yang, S.; Chen, Z.; Li, J.; Dong, A.; Gu, Y. Effects of Withdrawal Rate on the Microstructure of Directionally Solidified GH4720Li Superalloys. Materials 2019, 12, 771. https://doi.org/10.3390/ma12050771
AMA Style
Qu J, Yang S, Chen Z, Li J, Dong A, Gu Y. Effects of Withdrawal Rate on the Microstructure of Directionally Solidified GH4720Li Superalloys. Materials. 2019; 12(5):771. https://doi.org/10.3390/ma12050771
Chicago/Turabian StyleQu, Jinglong, Shufeng Yang, Zhengyang Chen, Jingshe Li, Anping Dong, and Yu Gu. 2019. "Effects of Withdrawal Rate on the Microstructure of Directionally Solidified GH4720Li Superalloys" Materials 12, no. 5: 771. https://doi.org/10.3390/ma12050771
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