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Solidification and Segregation Behaviors of Superalloy IN718 at a Slow Cooling Rate

1
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
2
Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Materials 2018, 11(12), 2398; https://doi.org/10.3390/ma11122398
Received: 12 November 2018 / Revised: 22 November 2018 / Accepted: 24 November 2018 / Published: 28 November 2018
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

The solidification and micro- and macro-segregation behaviors of as-cast INCONEL 718 (IN718) alloy at different temperatures under a slow cooling rate (5 °C/min) were investigated in this study. The results indicate that the solid-liquid interface grows into reticulation of hexagons during solidification. The variation trend of the solid fraction and transition rate of the solid phase with solidification time can be well characterized by the Boltzmann and Gaussian distribution, respectively. The order of segregation degree of negative segregation elements is: Fe > Cr > Al. Nb is the most principal positive segregation element, which is abundant in the long-term unsolidified remaining liquid. At the terminal stage of solidification, the increasing tendencies of the Nb and Mo contents in the liquid and the residual liquid density with decreasing temperature reverse due to the formation of the Laves phase. The freckles are most likely to form in the early stages of solidification, at which the liquid fraction is between 0.3 and 0.2, and the temperature range is about 1320 °C to 1310 °C. The information produced is expected to characterize the solidification and segregation behaviors of IN718 alloy when cooled at a slow rate characteristic of larger ingots typical of those required for industrial gas turbines and aircraft engines. View Full-Text
Keywords: INCONEL 718; solidification; segregation; slow cooling rate INCONEL 718; solidification; segregation; slow cooling rate
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Shi, X.; Duan, S.; Yang, W.; Guo, H.; Guo, J. Solidification and Segregation Behaviors of Superalloy IN718 at a Slow Cooling Rate. Materials 2018, 11, 2398.

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