Electron beam welding of as-cast AlCoCrFeNi2.1 and GH4169: microstructural evolution and mechanical performances of dissimilar joints

Sound electron beam welded joints were successfully fabricated between as-cast AlCoCrFeNi_2.1 eutectic high-entropy alloy and GH4169 superalloy. A systematic investigation was subsequently conducted into the influence of beam current (I_b) and welding speed (v) on the microstructure evolution and mechanical properties of the AlCoCrFeNi_2.1/GH4169 dissimilar electron beam joints. The optimal mechanical performance was achieved with an ultimate tensile strength of 878.3 MPa and a fracture strain of 27.4 %, under welding parameters of a 24 mA beam current, 12 mm/s welding speed, and a heat input of 114.0 J/mm. In joints with low heat input (Q < 114.0 J/mm), defects such as lack of penetration and incomplete fusion were exhibited, leading to a reduction in load-bearing capacity. Conversely, an excessively high heat input (Q > 114.0 J/mm) has been shown to triggers over-precipitation of brittle Laves phase in the fusion zone, thereby reducing the joint strength. The mean grain size in the fusion zone exhibited an increase from 32.8 μm to 38.1 μm in conjunction with an escalation in the applied heat input. The AlCoCrFeNi_2.1 eutectic high-entropy alloy demonstrated the highest degree of hardness (∼307HV), exceeding both the fusion zone (260-289HV) and the GH4169 zone (∼225HV).