Coupled thermo-mechanical finite simulation of heat treatment effects in wire-arc additively manufactured Inconel 625

A coupled thermo-mechanical finite element framework was developed to analyze the influence of heat treatment on the thermal history, phase evolution, and mechanical responses of Inconel 625 walls fabricated by wire arc additive manufacturing (WAAM). The model captures transient heat transfer, molten pool behavior, phase transformations, and the resulting residual stress and distortion fields. Mesh sensitivity analysis was performed to ensure numerical stability and computational efficiency. The simulations demonstrate that heat treatment promotes a more homogeneous phase distribution and stabilizes the arc process, resulting in a more uniform residual stress profile. Temperature fields increase nonlinearly with build height, and the stress state transitions from tensile near the substrate to compressive in upper layers. Distortion is more sensitive to heat treatment than residual stress, with notable reductions observed in thin-wall geometries. A multi-material configuration combining stainless steel and Inconel 625 was also modeled, revealing sharp interfacial transitions and characteristic morphological features consistent with experimental observations. Overall, the results provide mechanistic insight into heat-treatment-driven improvements in structural integrity, offering guidance for optimizing WAAM process parameters for both single- and multi-material builds.