Microstructure and mechanical properties of electron beam welding of AlCoCrFeNi2.1 eutectic high entropy alloy

Abstract

The dual-phase interleaved lamellar structure of the AlCoCrFeNi_2.1 eutectic high entropy alloy (EHEA) endows it with high strength, excellent plasticity and radiation resistance, thereby offering considerable potential as a structural material. Electron beam welding (EBW) is employed to fabricate homogenous welded joints of the heat-treated AlCoCrFeNi_2.1 EHEA. The experimental results indicate that the rapid cooling rate associated with EBW inhibits the diffusion of metal atoms and enhances the nucleation rate, thereby promoting the formation of a finer microstructure in the fusion zone (FZ). This markedly improves the mechanical properties of the welded joints, with the ultimate tensile strength of the welded joints exceeding that of the base material (BM). At a welding heat input of 123.5 J/mm, the ultimate tensile strength of the joint reaches a maximum of 990.3 MPa, resulting in a peak joint efficiency of 106.1 %. In comparison to the BM, the microhardness of the heat-affected zone (HAZ) exhibits a decrease of between 9.4 % and 11.4 %, while the microhardness of the FZ demonstrates an increase of between 10.0 % and 13.0 %. This study demonstrates the feasibility of employing EBW for the AlCoCrFeNi_2.1 EHEA, providing valuable insights for advancing its practical applications.