Significant Enhancement of Strength–Ductility Synergy of a Cost‐Effective Eutectic High‐Entropy Alloy via Strain‐Partition Engineering

Although eutectic high‐entropy alloys (EHEAs) enjoy superior mechanical properties, their compositional chemistry suffers from the presence of costly alloying elements. To overcome this drawback, developing cobalt‐free, cost‐effective EHEAs with superior mechanical properties is needed. For this purpose, the microstructure and properties of a cost‐effective (FCC + B2) AlCrFe 2 Ni 2 EHEA subjected to hybrid‐rolling (HR) are investigated herein. The total strain, corresponding to 90% thickness reduction, is imparted in the HR process in two equal steps: first cryo‐rolling and then warm‐rolling at 600 °C. The as‐cast material consists of lamellar (FCC + B2) eutectic and (B2(I) + B2(II)) spinodal regions. HR process results in a heterogeneous ultrafine/nanostructure featuring surviving spinodal and transformed duplex regions. The duplex regions consist of ultrafine recrystallized FCC, fragmented B2 lamellae, and dynamically nucleated B2 grains. The heterogeneous microstructure due to HR results from pronounced strain‐partitioning during the cryo‐rolling step, which, in turn, accelerates preferential recrystallization and selective transformation during the subsequent warm‐rolling step. The heterogeneous EHEA shows a significantly enhanced strength–ductility combination (yield strength: 1365 MPa; ultimate tensile strength: 1622 MPa; elongation: 12%), markedly better than the cobalt‐containing HEAs and EHEAs. The systematic kernel average misorientation analysis of the interrupted tensile tested specimens of the HR‐processed EHEA indicates pronounced hetero‐deformation‐induced strengthening.