Journal Article

PUBDB-2025-04776

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Synergistic microstructure refinement and enhanced mechanical properties in hypoeutectic Al–Si-based alloys via high-entropy microstructure refiner

Kim, J. K. ; Shadangi, Y. ; Kim, M. S. ; Lee, M. J. ; Park, E. S. (Corresponding author)Extern*

2025
Elsevier Rio de Janeiro

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Please use a persistent id in citations: doi:10.1016/j.jmrt.2025.08.039  doi:10.3204/PUBDB-2025-04776

Abstract: As the demand for lightweight and energy efficiency in Al–Si-based alloys continues to grow, the T5 heat treatment is increasingly preferred instead of T6, owing to its streamlined processing and reduced susceptibility to product distortion. Nevertheless, T5 treatment presents challenges in managing coarse α-Al dendritic structures and eutectic Si phases. Although commercial refiners like Al–Ti–B and Sr are used for microstructural refinement, there is a critical need for more effective refiners for multi-phase manipulation. Herein, we report a novel high-entropy microstructure refiner (HMR) that enables synergistic microstructure refinement under T5 heat treatment for hypoeutectic Al–Si alloys. In particular, the (TiZrNb)$_2$(CrFeNi) HMR, which combines Group A elements (Ti, Zr, Nb) to decrease ΔT$_N$ (nucleation undercooling, quantitatively validated by DSC) by forming heterogeneous nucleation sites and Group B elements (Cr, Fe, Ni) to induce ΔT$_C$ (constitutional undercooling) through segregation at the liquid/solid interface (verified through EPMA), achieves synergistic multi-phase microstructure refinement. This refinement simultaneously reduces the size of α-Al dendrites (to about one-tenth), secondary dendrite arm spacing (by about half), and eutectic Si spacing (by about half) while maintaining low intermetallic compound precipitation, compared to hypoeutectic Al–Si base alloy. This synergistic microstructure refinement simultaneously increases both yield strength (and ultimate tensile strength) and elongation, thus overcoming the typical trade-off among these properties. We believe that the results of this study provide an effective guideline for the development of cast (or T5-treated) aluminum alloys based on the application of novel HMRs, resulting in a cost-effective, streamlined post-process.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
2. FS-Proposal: I-20231069 (I-20231069) (I-20231069)

Experiment(s):

1. PETRA Beamline P21.1 (PETRA III)

Appears in the scientific report 2025

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