Wire and arc additive manufacturing (WAAM) is efficient for producing complex, large-scale metal parts, but the inherent repeated thermal cycling makes it difficult to achieve desired microstructural and mechanical characteristics. The microstructural evolution and mechanical properties of high-strength low-alloy steel during WAAM were investigated using a combined experimental and finite-element simulation approach, which particularly highlights the role of interlayer dwell time. The results demonstrate that reducing the dwell time increases the interpass temperature and intensifies thermal accumulation. Due to the repeated heating and cooling cycles during WAAM, the microstructures vary significantly along the building direction. Proeutectoid ferrite, grain boundary ferrite and bainite were the predominant phases, accompanied by a minor fraction of retained austenite. Anisotropic mechanical properties are observed in WAAM-fabricated steel components. Specimens from the middle region exhibit greater elongation but lower tensile strength than those from the bottom and top regions. Vertical tensile specimens, compared with horizontal ones, exhibit similar strength but reduced elongation, which can be attributed to interlayer structural imperfections. The fractured tensile specimens across all distinct regions exhibited a ductile fracture model. The study offers valuable insights into automating process parameter tuning to regulate the thermal effects during WAAM, thereby allowing accurate control of microstructural and mechanical properties.
Liu et al. (Mon,) studied this question.