The effect of ultra-dilute boron addition on solidification behavior and toughness of a laser powder bed fused eutectic high-entropy alloy

The effect of ultra-dilute boron addition on solidification behavior and toughness of a laser powder bed fused eutectic high-entropy alloy

Acta Materialia

10.1016/j.actamat.2026.122439

https://doi.org/10.1016/j.actamat.2026.122439

Siyuan Wei, Delvin Wuu, Verner Soh, Kwang Boon Lau, Jinliang Du, Moses J. Paul, Yingzhi Zeng, Maohang Zhang, Baicheng Zhang, Michael P. Short, Andrew Ngo, Upadrasta Ramamurty, Pei Wang

11 June 2026

Wei, S., Wuu, D., Soh, V., Lau, K. B., Du, J., Paul, M. J., Zeng, Y., Zhang, M., Zhang, B., Short, M. P., Ngo, A., Ramamurty, U., & Wang, P. (2026). The effect of ultra-dilute boron addition on solidification behavior and toughness of a laser powder bed fused eutectic high-entropy alloy. Acta Materialia, 316, 122439. https://doi.org/10.1016/j.actamat.2026.122439

Maintaining structural integrity and damage tolerance remains a critical challenge in the additive manufacturing of eutectic high-entropy alloys (EHEAs), where residual-stress-driven distortion and microstructural brittleness can limit robust fabrication and mechanical reliability. Here, we show that ultra-dilute boron addition provides a significant effect on tuning the solidification pathway of AlCoCrFeNi2.1 during laser powder bed fusion. Guided by thermodynamic calculations, boron is identified as a solute rejected by both eutectic phases, which expands the solidification interval (ΔT) and promotes elemental diffusion during rapid solidification. These effects sta bilize cellular–lamellar heterostructures, suppress microstructural embrittlement, and alleviate residual stress accumulation. As a result, the engineered microstructure achieves a yield strength of ~1342 MPa and a fracture toughness (KIC) of ~74.4 MPa⋅√m, surpassing those of reported eutectic alloys. This work demonstrates a ΔT- guided minor-alloying strategy, showing that ppm-level compositional tuning can generate disproportionate improvements in the toughness and structural robustness of an additively manufactured EHEA.

Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

This research / project is supported by the A*star - 4D Additive Manufacturing of Smart Structures-WP3
Grant Reference no. : M24N3b0028

This research / project is supported by the A*star - Advanced Alloys and Coatings for Structural and Functional Applica tions in Extreme Environments
Grant Reference no. : M25P1a0081

https://oar.a-star.edu.sg/communities-collections/articles/23383

1359-6454

Institute of Materials Research and Engineering