Effect of cellular structure on the microstructure and mechanical performance of W-doped single-phase Co-based high-entropy alloy prepared by selective laser melting

The Co–Cr–Fe–Ni high-entropy alloy (HEA) system, especially the Co-based face-centered cubic (FCC) HEAs, shows superior plasticity but relatively low mechanical strength. Recently developed additive manufacturing technology offers advantages in both efficient manufacturing and precise microstructure regulation. Here, we introduced a cellular structure into the single-phase Co 42 Ni 23 Cr 27 W 6 Fe 2 HEA by adding W as an element with a positive heat of mixing and regulating the parameters for selective laser melting (SLM). The additively manufactured samples exhibited refined grains with bamboo-like features and a cellular structure with elemental segregation and a high density of locations such as subgrain boundaries. In comparison with the as-cast sample, the cellular structure endowed the SLM-fabricated sample with a significantly increased yield strength and an ultimate tensile strength exceeding 1 GPa, as revealed by in-situ electron backscatter diffraction (EBSD) analyses. However, the dislocation pileup around the cellular boundaries could result in reduced plasticity. This study discusses the formation mechanism of the different structural and compositional features from the perspective of thermodynamics and kinetics and provides guidance for microstructure adjustment of metallic materials prepared by SLM.