Decoding Microstructural Heterogeneity and Mechanical Anomalies in GMAW of AISI 1010 Steel through Multi-Technique Characterization

This study explores the microstructural evolution and mechanical behavior of Gas Metal Arc Welded (GMAW) joints in AISI 1010 low-carbon steel to assess weld integrity and performance. A comprehensive evaluation combining optical microscopy, Rockwell B hardness profiling, Optical Emission Spectroscopy (OES), tensile testing, Charpy impact testing, and Scanning Electron Microscopy (SEM) was conducted. The weld zone (WZ) exhibited dendritic solidification and recorded the highest hardness, while the heat-affected zone (HAZ) showed a significant reduction due to thermal softening and grain coarsening. Tensile testing revealed a peak strength of 461.14 MPa, with fracture localized in the WZ, indicating it as the weakest region under axial loading despite its higher hardness. Face bend testing confirmed overall ductility, although surface cracking and delamination at the weld interface indicated incomplete fusion and internal discontinuities. SEM analysis revealed mixed-mode fracture behavior, including ductile dimples, cleavage planes, and intergranular tearing. Charpy impact testing at sub-zero temperatures further confirmed reduced fracture toughness in the fusion zone. These findings underscore that while GMAW can produce structurally sound joints in AISI 1010 steel, localized heterogeneities—particularly within the WZ—may compromise reliability. With optimized process control and defect monitoring, GMAW remains a viable and cost-effective welding solution for low-carbon steel structural applications.