About this Abstract |
| Meeting |
2027 TMS Annual Meeting & Exhibition
|
| Symposium
|
Chemistry and Physics of Interfaces
|
| Presentation Title |
Deformation mechanisms of directionally solidified near-eutectic NiCoCrAl medium entropy |
| Author(s) |
Seung Min Han, In Hyeok Yeo, Dae Ho Kim, Ho Jae Kwak |
| On-Site Speaker (Planned) |
Seung Min Han |
| Abstract Scope |
Near-eutectic high- and medium-entropy alloys containing brittle primary phases typically exhibit high strength but severely limited ductility. Here, we demonstrate that controlling the morphology of brittle B2 primary dendrites enables simultaneous enhancement of strength and ductility in a near-eutectic NiCoCrAl medium-entropy alloy. In-situ synchrotron X-ray imaging during directional solidification revealed how the thermal gradient orientation governs primary dendrite growth direction and secondary and tertiary arm development, dictating dendrite connectivity. Fracture behavior varied with dendrite geometry: crack propagation depended on dendrite connectivity and the availability of ductile eutectic ligaments. Micropillar compression coupled with TEM analysis revealed multiple strengthening mechanisms, including stacking fault formation in the L1₂ phase, a deformation-induced B2-to-L1₀ martensitic transformation accompanied by detwinning and periodic antiphase boundary formation, and strong dislocation blocking at incoherent phase boundaries. These findings establish dendrite connectivity as a design parameter for simultaneous high strength and ductility in near-eutectic alloys with brittle primary phases. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
High-Entropy Alloys, Mechanical Properties, Characterization |