Effect of Laser Energy Density on Microstructure and Mechanical Properties of FeCrNi Medium Entropy Alloy

FeCrNi medium entropy alloy (MEA) was prepared by selective laser melting (SLM) method, and the microstructure and mechanical properties of the FeCrNi MEAs under different laser energy density were investigated. The results show that the as-SLMed samples have a single-phase FCC structure and show a hierarchical microstructure of micro-scale matrix grains and submicron-scale cellular grains. The density of the as-SLMed samples is greatly affected by the energy density, which will increase rapidly and then decrease slowly with the increasing energy density. Energy densities between 45 and 80 J/mm 3 are considered to be the optimum process window for preparing the FeCrNi MEA, which show good combination of strength ( σ 0.2 > 720 MPa, σ UTS > 950 MPa) and ductility ( ε f = 20 ~ 40%). The high-density boundary networks from coarse matrix grains and fine cellular grains are the main reason for the high strength and the outstanding plasticity is due to the highly activated deformation twinning behavior resulting from the FCC matrix.