Assessing Hydrogen Embrittlement in AFSD-Fabricated AA7075 Aluminum Alloy Exposed to 3.5 wt.% NaCl

Additive friction stir deposition (AFSD) is a solid-state, layer-by-layer deformation process that has been widely accepted due to its ability to produce metallic materials with superior mechanical properties. This study focuses on the susceptibility of AFSD-processed AA7075 aluminum alloy to hydrogen embrittlement. The hydrogen charging was done by subjecting a dog-bone-shaped tensile test coupon to cathodic pre-charging for 24 h at a constant cathodic potential of -1.4 V in 3.5 wt.% NaCl solution at room temperature. It was followed by quasi-static tensile testing of the hydrogen-charged coupons (while hydrogen charging of tensile coupons continued) at different strain rates at room temperature. Thermal desorption spectroscopy was performed to elucidate the various hydrogen trapping sites present in the AFSD-processed AA7075 aluminum alloy. A comparative study was performed using the AFSD feedstock rod by subjecting it to a hydrogen embrittlement study under similar test conditions. Scanning electron microscope (SEM), electron backscattered diffraction (EBSD), and transmission electron microscope (TEM) were employed for microstructural characterization. The comparative analysis revealed the effect of AFSD process on hydrogen embrittlement behavior and provided important insight into the role of the AFSD process in mitigating hydrogen embrittlement in AA7075. Computational modeling is currently underway to validate the experimental results and to provide atomic‑scale insights into the interaction of hydrogen with AFSD‑processed AA7075.