Gas tungsten arc welding of as-cast AlCoCrFeNi2.1 eutectic high entropy alloy

The AlCoCrFeNi2.1 eutectic high entropy alloy is of great interest due to its unique mechanical properties combining both high strength and plasticity. Here, gas tungsten arc welding was performed for the first time on an as-cast AlCoCrFeNi2.1 alloy. The microstructural evolution of the welded joints was assessed by combining electron microscopy with electron backscatter diffraction, synchrotron X-ray diffraction analysis and thermodynamic calculations. Microhardness mapping and tensile testing coupled with digital image correlation were used to investigate the strength distribution across the joint. The base material, heat affected zone and fusion zone are composed of an FCC + B2 BCC eutectic structure, although the relative volume fractions vary across the joint owing to the weld thermal cycle. The BCC nanoprecipitates that existed in the base material started to dissolve into the matrix in the heat affected zone and closer to the fusion zone boundary. Compared to the as-cast base material, the fusion zone evidenced grain refine-ment owing to the higher cooling rate experienced during solidification. This translates into an increased hardness in this region. The joints exhibit good strength/ductility balance with failure occurring in the base material. This work establishes the potential for using arc-based welding for joining eutectic high entropy alloys.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Automated summary

This study investigated the gas tungsten arc welding of an as-cast AlCoCrFeNi2.1 alloy and analyzed the microstructural evolution and strength distribution of the welded joints. The results showed that the weld thermal cycle caused variations in the relative volume fractions of the FCC + B2 BCC eutectic structure across the joint. BCC nanoprecipitates in the base material dissolved into the matrix in the heat affected zone and closer to the fusion zone boundary. The fusion zone exhibited grain refinement and increased hardness compared to the as-cast base material. The joints demonstrated a good balance of strength and ductility with failure occurring in the base material. This study establishes the potential for using arc-based welding for joining eutectic high entropy alloys.