Homogenization heat treatment for an additively manufactured precipitation-hardening high-entropy alloy

A precipitation-hardening high-entropy alloy (HEA), (FeCoNi) 86 Al 7 Ti 7 , was successfully fabricated using selective laser melting (SLM). Severe segregation of Ti occurred at the boundaries of dislocation cells. Therefore, homogenization heat treatment at 1150 °C for 0.5 h was performed to alleviate the microsegregation. After homogenization, almost no dislocation cells were left in the grains, and recrystallization occurred as the average grain size increased from 37 to 54 μm. Compared with the initial as-built HEA, the ductility of the HEA increases significantly from 29% to 40%, and the strength decreases slightly from 710 to 606 MPa. For further aging, pre-homogenization can decrease the precipitation of ordered L2 1 phases. Because void has a high propensity to initiate from the matrix/L2 1 incoherent interface, pre-homogenization reduced the number of weak points, thus considerably improving the plastic deformation ability of the aged HEA by 36%. In addition, the strengthening mechanism has also been analyzed for the aged HEA. It was revealed that the coherent L1 2 precipitate contributed the most to the increased strength. Graphical abstract