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Title: | Control of discontinuous and continuous precipitation of γʹ-strengthened high-entropy alloys through nanoscale Nb segregation and partitioning | Authors: | Fan, L Yang, T Luan, JH Jiao, ZB |
Issue Date: | 15-Aug-2020 | Source: | Journal of alloys and compounds, 15 Aug. 2020, v. 832, 154903 | Abstract: | Control of discontinuous and continuous precipitation of L12-ordered γʹ precipitates is crucial for tailoring microstructure and mechanical properties of coherent precipitation-strengthened high-entropy alloys (HEAs). In this study, we show that the appropriate addition of Nb not only suppresses discontinuous γʹ precipitation through grain boundary segregation but also promotes continuous γʹ precipitation through nanoscale solute partitioning, leading to substantially improved mechanical properties of the HEAs. Specifically, we explore the effects of Nb on the discontinuous and continuous precipitation microstructures, grain boundary segregation, and mechanical properties of (CoCrFeNi)94-xAl3Ti3Nbx (x = 0, 0.4, 0.8, 1.6, and 2.3 at.%) HEAs. Atom probe tomography reveals that Nb exhibits preferential segregation at grain boundaries of HEAs, which substantially inhibits the grain boundary precipitation and migration due to the reduction of grain boundary energy and solute drag effect, thereby suppressing discontinuous γʹ precipitation at the grain boundaries. Moreover, Nb partitions to the continuous γʹ nanoparticles in grain interiors, which leads to a high chemical driving force for continuous γʹ precipitation. Because of these beneficial effects, Nb-modified HEAs with a uniform distribution of γʹ nanoparticles throughout the matrix were developed, and the correlation between the precipitate microstructure and mechanical properties of these HEAs is discussed. | Keywords: | Atom probe tomography Grain boundary segregation High-entropy alloy Nanoscale precipitation Precipitation strengthening |
Publisher: | Elsevier BV | Journal: | Journal of alloys and compounds | EISSN: | 0925-8388 | DOI: | 10.1016/j.jallcom.2020.154903 | Rights: | © 2020 Elsevier B.V. All rights reserved. © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/. The following publication Fan, L., Yang, T., Luan, J. H., & Jiao, Z. B. (2020). Control of discontinuous and continuous precipitation of γʹ-strengthened high-entropy alloys through nanoscale Nb segregation and partitioning. Journal of Alloys and Compounds, 832, 154903 is available at https://doi.org/10.1016/j.jallcom.2020.154903. |
Appears in Collections: | Journal/Magazine Article |
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Fan_Control_Discontinuous_Continuous.pdf | Pre-Published version | 4.83 MB | Adobe PDF | View/Open |
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