Adaptive Heat Input‐Based Optimization of Microstructure and Mechanical Properties of Low‐Carbon Steel Fabricated by Wire Arc Additive Manufacturing

This study proposes an adaptive heat input (AHI) process for cold metal transfer (CMT)‐based wire arc additive manufacturing (WAAM) of low‐carbon steel to mitigate microstructural inhomogeneity and mechanical anisotropy caused by uneven heat accumulation. Cooling rate control was optimized via the combination of thermo‐mechanical simulation and experimental validation. In comparison to constant heat input (CHI), the AHI process yielded higher molten pool temperatures and a more uniform longitudinal stress distribution, owing to stabilized thermal gradients. This process significantly promoted acicular ferrite formation, increasing its volume fraction by 238.7%, and eliminated interlayer Widmanstätten ferrite, thereby substantially improving microstructural homogeneity. Relative to the CHI process, the AHI process improved yield strength and ultimate tensile strength along the 0° direction, with standard deviations reduced by 15.0% and 18.7%, respectively; along the 90° direction, the corresponding reductions were 47.5% and 87.1%. The proposed AHI strategy offers a robust pathway for fabricating high‐performance low‐alloy steel components via WAAM.