Manipulating nanostructure during wire arc additive manufacturing defeats hydrogen embrittlement
Mahdieh Safyari, Fabio Haunreiter, Shogo Furuta, Pei Loon Khoo, Florian Mayrhofer, Masakazu Kobayashi, Masoud Moshtaghi
Abstract
Wire arc additive manufacturing (WAAM) leads to a unique nano/microstructure. The combination of multiscale experimental and numerical analyses firstly shows that the intrinsic heat treatment during WAAM leads to an unusual depletion of Mg near the grain boundaries. During the WAAM process, a high dislocation density leads to formation of sub-grains and high-angle grain boundaries (HAGBs). It is revealed that the uniformly distributed micropores formed during the WAAM are strong hydrogen traps. The reduction in Mg content at the HAGBs, an increase in total length of HAGBs and hydrogen trapping by micropores help to defeat intergranular hydrogen embrittlement by WAAM. • Hydrogen embrittlement (HE) of additively manufactured Al-Mg alloy is studied. • Wire arc additive manufacturing (WAAM) results in unique nano/microstructure. • Intrinsic heat treatment in WAAM leads to Mg-depletion near grain boundaries. • WAAM leads to increase in total length of high-angle grain boundaries (HAGBs). • Mg-depletion zones, micropores and HAGBs contribute to HE suppression by WAAM.