Manipulating nanostructure during wire arc additive manufacturing defeats hydrogen embrittlement

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.