Abstract:Wire arc additive manufacturing (WAAM) has emerged as a promising approach for fabricating large-scale components. However, conventional WAAM still faces challenges in optimizing microstructural evolution, minimizing additive-induced defects, and alleviating residual stress and deformation, all of which are critical for enhancing the mechanical performance of the manufactured parts. Integrating interlayer friction stir processing (FSP) into WAAM significantly enhances the quality of deposited materials. However, numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient. A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM. The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively. Moreover, the residual stress distribution and deformation behavior under both single-layer and multi-layer deposition conditions were investigated. Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted. Results show that subsequent layer deposition induces partial remelting of the previously solidified layer, whereas FSP does not cause such remelting. Furthermore, thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components, thereby improving their structural integrity and mechanical properties.