Enhanced microstructure and mechanical properties of AZ31 magnesium alloy joints using rare earth enriched filler produced by GTAW

• Developed and investigated GTAW joints of AZ31 magnesium alloy using novel Mg-3Nd-1.5Gd-0.5Zr-0.3 Zn filler material, enhancing mechanical properties and microstructural characteristics. • Achieved refined grain structure in AZ31 weld zones with reduced porosity and improved hardness through the incorporation of rare earth elements. • Demonstrated superior yield strength, tensile strength, and work hardening behavior in the weldments compared to conventional fillers. • Identified the critical role of secondary phase precipitation and strain hardening in enhancing weld performance. This study explores the influence of a novel Mg-3Nd-1.5Gd-0.5Zr-0.3 Zn filler material (Mg RE filler 1) on the microstructure, mechanical properties, and fracture behavior of AZ31 magnesium alloy joints welded using Gas Tungsten Arc Welding (GTAW) process. The objective was to evaluate the rare earth (RE)-rich filler elements (Nd, Gd, and Zr) improve weld quality compared to conventional fillers (AZ31 and AZ61). The methodology involved welding AZ31 Mg alloy plates with three different fillers. The welded joints were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Electron Backscatter Diffraction (EBSD), and Scanning Electron Microscopy (SEM). Mechanical properties were assessed through tensile tests, microhardness measurements, and fractography analysis. The results reveal that the Mg-3Nd-1.5Gd-0.5Zr-0.3 Zn filler significantly improved the grain refinement in the weld zone due to enhanced dynamic recrystallization (DRX) and the Zener pinning effect caused by fine RE-rich precipitates. The weldments produced with this filler exhibited higher tensile strength (3–9 % improvement), superior microhardness, and enhanced strain-hardening response when compared to those produced with AZ31 and AZ61 fillers. Fractography analysis from SEM results revealed a transition from brittle to ductile fracture behavior, confirming the improved weld integrity. It is recommended that the Mg-3Nd-1.5Gd-0.5Zr-0.3 Zn filler be considered for industrial applications involving AZ31 alloy welding, particularly in advanced manufacturing sectors (aerospace and automotive), due to its superior mechanical performance and refined microstructure. Further investigations on corrosion resistance and long-term weld stability are suggested for future work.