Wire arc additive manufacturing of structural alloys: microstructure evolution, anisotropy control, sustainability, and AI-guided hybrid manufacturing

Abstract

Wire Arc Additive Manufacturing (WAAM) has emerged as a promising metal additive manufacturing technology for fabricating large-scale structural components owing to its high deposition rate, excellent material utilization, and cost-effectiveness. Compared with powder-based processes, WAAM offers significant advantages for producing complex metallic parts in aerospace, marine, automotive, energy, and oil and gas industries. However, challenges related to microstructural heterogeneity, mechanical anisotropy, residual stress, dimensional accuracy, and process repeatability continue to limit its widespread industrial adoption. This review critically examines recent advances in WAAM, emphasizing the relationships between processing parameters, microstructure evolution, mechanical behavior, intelligent process monitoring, hybrid manufacturing, and sustainability. The reviewed literature demonstrates that heat input, cooling rate, interpass temperature, and deposition strategy govern grain morphology, phase evolution, porosity, and residual stress, thereby significantly influencing the mechanical performance of aluminum, titanium, steel, and nickel-based alloys. Recent developments, including pulsed arc modes, Cold Metal Transfer (CMT), controlled cooling, and interlayer deformation, have shown considerable potential for reducing anisotropy and improving tensile properties and structural reliability. Furthermore, the integration of intelligent sensing techniques, machine learning algorithms, and digital twin technologies enables real-time process monitoring, predictive defect detection, and data-driven process optimization. Hybrid additive–subtractive manufacturing has also emerged as an effective strategy for enhancing dimensional accuracy, surface quality, and manufacturing efficiency while reducing post-processing requirements. Overall, this review highlights current industrial applications, sustainability benefits, existing technical challenges, and future research opportunities, demonstrating that the convergence of advanced process control, artificial intelligence, and hybrid manufacturing will be essential for achieving reliable, intelligent, and sustainable WAAM systems.