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

Abstract

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 Al19Co25Fe25Ni31 hypo-eutectic, Al20Co22Fe30Ni28 eutectic, and Al21Co22Fe29Ni28 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 Al20Co22Fe30Ni28 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) L12 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 L12 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.

Keywords

• Dual-wire arc additive manufacturing
• AlCoFeNi
• Eutectic high entropy alloys
• Microstructure
• Mechanical properties