A precipitation-strengthened high-entropy alloy for additive manufacturing

As newly developed metallic materials, several high-entropy alloys (HEAs) have been fabricated via additive manufacturing (AM) and have been found to exhibit more uniform microstructures and better mechanical properties than their as-cast counterparts. However, current additive-manufactured HEAs are relatively unsatisfactory in terms of strength owing to the inevitable micropores or microcracks that occur during their processing. A significant challenge is to further increase the mechanical properties of single-solid-solution HEAs for AM. In light of this, in the present study, a precipitation-strengthened Ni_2.1CoCrFeNb_0.2 HEA was designed that is particularly easy to print for use in AM. Bulk samples without observed defects were successfully produced by direct laser deposition. The as-deposited Ni_2.1CoCrFeNb_0.2 HEA showed an excellent strength-ductility combination. After proper heat-treatments, the tensile strength increased dramatically to ∼ 1127 MPa with a tensile elongation of ∼ 17 %, which is the best performance in the reported AM-fabricated HEAs. The precipitation of the γ″ phase was quantitatively analyzed to reveal the excellent strengthening effect in this new AM-fabricated HEA. In the present study, a superior precipitation-reinforced HEA with fully dense microstructures was successfully developed for AM. These results open up new possibilities for the further development of AM-fabricated HEAs.