Deposition strategy correlation with texture development, geometric homogeneity, and mechanical anisotropy in robotic WAAM-fabricated aluminum alloy thick walls

This research comprehensively examines the impact of deposition strategies on the microstructural evolution, geometric homogeneity, and mechanical properties of AA4043 aluminum alloy thick walls fabricated via robotic Wire Arc Additive Manufacturing (WAAM) using Cold Metal Transfer Gas Metal Arc Welding (CMT-GMAW). Utilizing unidirectional and bidirectional deposition techniques with a triangular weaving pattern, the study explores the influence of thermal gradients and solidification dynamics on grain morphology, texture development, porosity formation, silicon segregation, and mechanical anisotropy. Advanced characterization methods, including Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), and Energy Dispersive X-ray Spectroscopy (EDS), were employed to correlate the microstructural features with mechanical response characterized through uniaxial tensile tests and Vickers microhardness across different orientations. Fractography of fractured specimens elucidated failure mechanisms. Results indicated that unidirectional deposition promotes finer, relatively less elongated grains due to higher thermal gradients and rapid cooling rates, enhancing nucleation rates and leading to comparatively isotropic mechanical properties. In contrast, bidirectional deposition resulted in elongated grains aligned along the build direction, increased porosity, and pronounced silicon segregation at grain boundaries, culminating in anisotropic mechanical behavior. While unidirectional deposition promoted isotropic mechanical properties due to faster cooling rates and refined grain structure, bidirectional deposition offered superior geometric homogeneity and consistency, effectively minimizing the humping phenomenon. This improved geometric consistency leads to enhanced material-saving and sustainable manufacturing practices, as dimensional accuracy is critical in WAAM-fabricated structures. The scientific rationale behind these findings is supported by detailed microstructural analysis and mechanical testing, including hardness measurements and tensile testing. These results underscore the significance of deposition strategy in tailoring both the microstructure and geometric characteristics of WAAM components, contributing to the optimization of additive manufacturing processes for producing high-performance metallic components with minimal material wastage.