Achieving synergistic strength-ductility enhancement in a hierarchical hetero-lamellar AlCoCrFeNi2.1 eutectic high-entropy alloy via facile hot-rolling strategy

Abstract

Eutectic high-entropy alloys (EHEAs) have attracted considerable interest due to their superior multifunctional performance. However, the inherent tendency of stress concentration at irregular phase boundaries frequently leads to premature fracture. This study presents a facile hot-rolling strategy to achieve synergistic strength-ductility enhancement in AlCoCrFeNi_2.1 EHEA via constructing a hierarchical hetero-lamellar structure (HHLS). Through controlled per-pass rolling reduction (PPRD), we induce strain-partitioning-mediated microstructural refinement in the hot-rolled EHEA and activate synergistic deformation mechanisms including stacking faults, Lomer-Cottrell locks, and deformation twinning. The resultant HHLS (aligned FCC/B2 lamellae, partially recrystallized FCC regions, and intragranular B2 precipitates) triggers pronounced hetero-deformation-induced (HDI) strengthening. Consequently, the EHEA with HHLS exhibits exceptional properties: yield strength of 1202 MPa, ultimate tensile strength of 1489 MPa, and uniform elongation of 11.5 %, which are 112 %, 45 %, and 6 % higher than those of the as-cast alloy, respectively. The superior properties originate from HDI effect and FCC phase-mediated deformation mechanisms, which enable the EHEA to maintain exceptional work-hardening rate despite high dislocation density, effectively delaying plastic instability. These findings not only establish a readily implementable thermomechanical processing strategy for EHEAs, but also provide a novel paradigm for improving mechanical properties, paving the way for their application in high-performance structural materials.