Metallurgical enhancement and mechanical performance of GTAW of AA5083 plates using medium and high-entropy fillers

The contemporary investigation focusses on the development of a welding technique to join AA5083 alloy plates using equimolar medium entropy alloy (4E-MEA - Fe0.25Al0.25Ni0.25Cu0.25) and high entropy alloy (5E-HEA - Fe0.2Al0.2Ni0.2Cu0.2Ti0.2) filler wires. A man-made combined cable wire method, was chosen to prepare the filler wires and the gas tungsten arc welding was used to conjoin the AA5083 plates. This study evaluated the metallurgical characteristics and mechanical performance of welded joints using 4E-MEA and 5E-HEA filler weldments and compared them with the standard ER5356 filler weldment. XRD analysis showed that both 4E-MEA and 5E-HEA weldments had evolved BCC and FCC phases, whereas microstructural analysis revealed a fine grain distribution without intermetallic phases. SEM analysis of the weldments revealed a heterogeneous microstructure (equiaxed and columnar grains) owing to the influence of the constituent elements. Solid solution formation, structural refinement, and high configurational entropy effects promoted grain refinement in the weldments as evidenced by EBSD analyses. The microhardness of 4E-MEA and 5E-HEA weldments increased by 18.3% and19.89%, respectively, compared with the standard filler weldment, while the tensile strength of 4E-MEA and 5E-HEA weldments increased by 24.3% and 27.9%, respectively and also obtained work-hardening rates were higher. It was observed that the heterogeneous microstructure in the weldment led to complicated plastic deformation and improved the mechanical responses. The presence of Fe and Ni increased ductility and inhibited the formation of intermetallic. The fractography results showed that the 4E-MEA and 5E-HEA filler weldments exhibited a combination of ductile and brittle fractures. Overall, the researchers demonstrated that the developed equimolar 4E-MEA and 5E-HEA filler wires could produce weldments with improved mechanical properties and can be utilized in automobile and shipbuilding applications.