- [English]
- Hot-Cracking Behaviors in (CoNi)85Mo15 Medium-Entropy Alloys Manufactured via Powder Bed Fusion
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Seungjin Nam, Heechan Jung, Haeum Park, Chahee Jung, Jeong Min Park, Hyoung Seop Kim, Seok Su Sohn
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J Powder Mater. 2024;31(6):537-545. Published online December 31, 2024
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DOI: https://doi.org/10.4150/jpm.2024.00262
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 Abstract
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- Additive manufacturing makes it possible to improve the mechanical properties of alloys through segregation engineering of specific alloying elements into the dislocation cell structure. In this study, we investigated the mechanical and microstructural characteristics of CoNi-based medium-entropy alloys (MEAs), including the refractory alloying element Mo with a large atomic radius, manufactured via laser-powder bed fusion (L-PBF). In an analysis of the printability depending on the processing parameters, we achieved a high compressive yield strength up to 653 MPa in L-PBF for (CoNi)85Mo15 MEAs. However, severe residual stress remained at high-angle grain boundaries, and a brittle µ phase was precipitated at Mo-segregated dislocation cells. These resulted in hot-cracking behaviors in (CoNi)85Mo15 MEAs during L-PBF. These findings highlight the need for further research to adjust the Mo content and processing techniques to mitigate cracking behaviors in L-PBF-manufactured (CoNi)85Mo15 MEAs.
- [Korean]
- Effect of Building Orientation on Tensile Properties of Hastelloy X alloy Manufactured by Laser Powder Bed Fusion
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Seong-June Youn, GooWon Noh, Seok Su Sohn, Young-Sang Na, Young-Kyun Kim
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Received April 3, 2025 Accepted April 21, 2025 Published online April 21, 2025
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DOI: https://doi.org/10.4150/jpm.2025.00080
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Abstract
- In this study, the effect of build orientation on the mechanical properties of Hastelloy X fabricated by laser powder bed fusion (LPBF) process was investigated. Initial microstructural analysis revealed an equiaxed grain structure with random crystallographic orientation and annealing twins. Intragranular precipitates identified as Cr-rich M23C6 and Mo-rich M6C carbides were observed, along with a dense dislocation network and localized dislocation accumulation around the carbides. Mechanical testing showed negligible variation in yield strength with respect to build orientation; however, both ultimate tensile strength and elongation exhibited a clear increasing trend with higher build angles. Notably, the specimen built at 90° exhibited approximately 22% higher tensile strength and more than twice the elongation compared to the 0° specimen.
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