Microstructural evolution and mechanisms in additively manufactured AlCrCuFeNix complex concentrated alloys via selective laser melting

Abstract

This article discusses the influence of the Ni content on the microstructures of AlCrCuFeNix complex concentrated alloys prepared by selective laser melting. The microstructural evolution mechanisms were also uncovered. It is found that the as-built Ni1.0 alloy possesses equiaxed-columnar bimodal grain structures and basket-weave microstructure consisting of striped body-centered cubic (bcc) nano-precipitates and ordered bcc (B2) phase. Adding Ni triggers the lattice transition from B2 to face-centered cubic (fcc), leading to the change of the primary solidification phase from B2 to fcc beyond the critical content of Ni. Meanwhile, the striped bcc nano-precipitates inside the B2 lamellae gradually transform into spherical morphologies due to the consumption of Fe and Cr solutes in eutectic reaction. Furthermore, the microstructures change from hypo-eutectic (Ni2.0, Ni2.5) to near-eutectic (Ni3.0) to hyper-eutectic (Ni3.5), accompanied by a columnar-to-equiaxed transformation due to the large constitutional supercooling induced by the eutectic reaction.