Submerged friction stir processing of wire arc additively manufactured Al alloy: Microstructure and mechanical properties

Friction stir processing (FSP) significantly improves the microstructure and mechanical properties of wire arc additive manufacturing (WAAM) components. This study pioneers the application of submerged friction stir processing (SFSP) to thin-walled WAAM components fabricated from Al-2319, Al-5087, and Al-6082 alloys. The samples were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and microindentation. The results demonstrate that SFSP leads to a break of the eutectic network, the uniform distribution of precipitates originating from the Al matrix, a marked reduction in porosity and cracks, and grain refinement attributed to accelerated dynamic recrystallization, enhancing hardness and ductility across all three alloys. The improvement was most notable in the Al-6082 alloy relative to the others. Water cooling delays precipitates formation and encourages the development of fine particles. The uncoarsened theta' phase in Al-2319 and the fine beta' phase in Al-5087 both contribute to superior tensile properties.