Anisotropic mechanical behaviour and microstructure evolution of dissimilar DSS-2507/IN-625 developed through twin-wire arc additive manufacturing route

Simultaneous deposition of DSS-2507 and IN-625 by twin-wire arc additive manufacturing (T-WAAM) offers a promising route for dissimilar structures with tailored performance. This study investigates the processing–microstructure–property relationship of an in-situ alloyed DSS-2507/IN-625 wall fabricated using GMAW-based T-WAAM, focusing on crystallographic evolution, phase stability, and mechanical anisotropy. XRF confirmed compositional uniformity, while XRD and EBSD revealed a stable γ-FCC matrix with trace ferrite (<0.2%), indicating effective in-situ alloying and suppression of detrimental phases. EBSD demonstrated a consistent ~45° preferred grain orientation, uniform grain size (~10 µm), and homogeneous phase distribution along the build height, confirming stable epitaxial growth. The wall exhibited microhardness of 209–221 HV, ultimate tensile strength up to 895 MPa, impact energy of 31.6–32.8 J, and residual tensile stress of 358–587 MPa. The mechanical response was governed by γ-phase stabilization, solid-solution strengthening, crystallographic texture, and Hall–Petch grain-boundary strengthening.