Towards understanding the process‒structure–property relationships underlying forging-like build-direction ductility in heat-treated additive friction stir deposited AA7050

Additive friction stir deposition (AFSD) has emerged as a promising technology for rapid point-of-need fabrication of large structural components from high-strength aluminum alloys. Recent work has demonstrated that lubricant-free twin-rod AFSD of AA7050 combined with a customized post-deposition heat treatment (PDHT) can achieve forging-like build-direction (BD) mechanical properties. However, the microstructural origins of this behavior remain poorly understood. This work investigates the process-structure-property relationships governing the mechanical performance of PDHT AFSD AA7050 through analysis of builds with equivalent processing parameters that exhibit high and low BD ductility. Microstructural characterization, including electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS), is coupled with nanoindentation to link microstructural features such as grain size, misorientation, crystallographic texture, and local elemental segregation, with localized mechanical behavior. These observations are correlated with in-situ thermomechanical processing data collected during deposition to elucidate how processing influences the microstructural factors governing mechanical behavior. The results provide insight into the origins of forging-like mechanical performance in AFSD AA7050 and inform future optimization of solid-state additive manufacturing of high strength aluminum alloys.