A Comparative Study of Microstructure Evolution and Mechanical Performance in High‐Strength Low‐Alloy Steel Fabricated via Laser‐Based Wire Additive Manufacturing and Arc‐Based Wire Additive Manufacturing

Understanding how heat‐source characteristics control microstructure and properties is essential for selecting wire‐fed additive manufacturing routes for high‐strength low‐alloy steels. Here, ER120S‐G steel walls were fabricated by cold metal transfer wire arc additive manufacturing (WAAM–CMT) and wire laser additive manufacturing (WLAM), and their phase constitution, grain structure, texture, local misorientation, and tensile properties were compared. WAAM‐CMT produced bainitic ferrite and granular bainite because of its higher heat input and slower cooling rate. By contrast, WLAM generated refined tempered martensite with weaker texture, a higher fraction of low‐angle grain boundaries, and stronger local lattice distortion. Consequently, WLAM achieved a yield strength of 759.6 MPa and an ultimate tensile strength of 1114.3 MPa, markedly higher than those of WAAM‐CMT, 544.8 and 665.1 MPa, while maintaining a comparable uniform elongation of 23.3%. The enhanced strength–ductility balance of WLAM is attributed to martensitic transformation, grain refinement, and defect‐assisted strengthening. This study establishes a direct process–microstructure–property correlation between WAAM–CMT and WLAM, providing guidance for manufacturing high‐strength steel components by wire‐fed additive manufacturing.