Unraveling atomic-scale crystallization and microstructural evolution of selective laser melted FeCrNi medium-entropy alloy
Selective laser melting (SLM) provides a flexibility to manufacture the components with complex structures. However, the unexpected crystallization and the dynamical microstructural evolution at atomic scale still remains unknown during the SLM process. Here, the crystallization and formation mechanism of equimolar FeCrNi medium-entropy alloy (MEA) with excellent mechanical properties prepared by SLM are studied via molecular dynamics (MD) simulations. The surface morphology, atomic microstructural evolution, and Cr element segregation are investigated during the crystallization process. The crystallization and microstructural characteristic are clearly observed. A large number of the stacking faults take place in the boundary of the melting pool, but some stacking faults extend to the center region due to the thermal gradient effect. A segregation phenomenon of the nanoscale Cr-rich cluster occurs in the FeCrNi MEA, to reveal the precipitation dynamic mechanism during the SLM process. Furthermore, the higher energy density and lower scanning speed would promote the segregation and even form a mesh connected structure. The current result provides an insight into the crystallization and formation mechanism of microstructure to develop the advanced alloys with high strength and toughness via the reasonable choice of SLM parameters.