Achieving enhanced strength-ductility synergy in an additive manufactured eutectic compositionally complex alloy via optimizing alloy composition

Additive manufacturing of metallic materials creates structures layer-by-layer through rapid melting and solidification, which can promote refined microstructure and enhanced strength. This study investigates the impact of regulating Co content on microstructural evolution and mechanical properties in eutectic AlCoCrFeNi_2.1 compositionally complex alloy (CCA) fabricated through laser engineered net shaping technique. Our work clearly demonstrates that subtly regulating Co content can significantly manipulate the lamellar spacing and phase volume fraction, resulting in enhanced strength-ductility combination. Notably, compared with the original eutectic AlCoCrFeNi_2.1 CCA with a tensile strength at ∼883 MPa and fracture elongation at ∼11 %, our designed AlCo_1.2CrFeNi_2.1 CCA with a higher Co content exhibits superior strength-ductility synergy, showing a remarkable tensile strength at ∼1602 MPa and fracture elongation at ∼14 %. This increased Co concentration promotes lamellar refinement and introduces more phase boundaries in the FCC/BCC dual-phase microstructure, which induce strengthening effect through dislocation pile-up at the phase boundaries. Meanwhile, the coherent interfaces between FCC and BCC facilitate dislocation propagation across the phase boundaries and support strain accommodation, ultimately achieving an exceptional strength-ductility balance. Our findings provide valuable insights for further design and rapid development of high-performance additive-manufactured alloys by adjusting the elemental composition.