CoFeNi twisted wire plus Al wire arc additive manufacturing of AlCoFeNi eutectic and near-eutectic high entropy alloys

This paper is the first attempt to fabricate eutectic high entropy alloy (EHEA) using dual -wire arc additive manufacturing (D-WAAM) technology with twisted wire + single wire. Using CoFeNi twisted wire and Al single wire as raw materials, the eutectic point was determined by adjusting the Al content over a wide range by adjusting the speed of the Al single wire. We designed and fabricated Al 19 Co 25 Fe 25 Ni 31 hypo-eutectic, Al 20 Co 22 Fe 30 Ni 28 eutectic, and Al 21 Co 22 Fe 29 Ni 28 hyper-eutectic high entropy alloys, and conducted in-depth research on their mechanical properties and microstructure. With increasing Al content, the microstructural changes from hypo-eutectic to hyper-eutectic, the strength of the alloy increases, and the plasticity of the alloy decreases. The fabricated Al 20 Co 22 Fe 30 Ni 28 EHEA shows the best strength-plastic balance. This characteristic is mainly attributed to the eutectic alloy exhibiting a dual-phase lamellar microstructure consisting of an ordered face-centered cubic (FCC) L1 2 phase with a volume fraction of 56.9% and an ordered body-centered cubic (BCC) B2 phase with a volume fraction of 43.1%. Because the alloy contains both the hard B2 phase and the tough L1 2 phase, the room temperature tensile strength reaches 1041 MPa, and the plasticity reaches 14.9%, which is higher than those of other EHEAs fabricated by casting and arc melting. The excellent strength and plasticity of these materials show great potential in engineering applications. This approach not only expands the existing additive manufacturing technology but also provides new ideas for the additive manufacturing of EHEAs.