Pore formation and evolution in wire plus arc additively manufactured 2319 Al alloy

Given its detrimental influence on mechanical properties, porosity defect is a major problem for wire + arc additively manufactured (WAAM) Al components. We performed X-ray computed tomography, optical microscopy, and scanning electron microscopy to observe the spatial distribution, size, and shape of micropores and reveal their formation and evolution mechanisms during the deposition and heat treatment of the WAAM 2319 Al alloys. Key findings demonstrated that thehydrogenmicropores and solidification microvoids existed in as-deposited alloys. The amounts and morphologies of hydrogen micropores and solidification microvoids varied from the top, middle, and bottom of the wall sample because of the distinct microstructure and second-phase distribution in each section. After the heat treatment, a significant variation in micropores involving three main evolution mechanisms, namely, hydrogen micropore precipitation, phase particle dissolution, and micropore growth, was observed. The hydrogen content analysis verifies that the evolution of micropores from each section of the wall was dominated by different mechanisms. Results of this research may provide a solid foundation for the safe application of WAAM Al alloy structures.