Investigating Hydrogen Embrittlement of AA7075 Aluminum Alloy Processed using Additive Friction Stir Deposition

Additive friction stir deposition (AFSD) is a solid-state deformation process route that has gained popularity due to its potential to manufacture metallic materials with improved mechanical properties. This research focuses on the susceptibility of AA7075 aluminum alloy processed via AFSD to hydrogen embrittlement. The hydrogen charging was conducted by subjecting dog-bone-shaped tensile test specimens to cathodic pre-charging for 24 h at a constant 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 specimens (while hydrogen charging of the tensile specimens continued) at different strain rates at room temperature. For comparison, AA7075-T6 (used as a feedstock during AFSD) was subjected to a hydrogen embrittlement study under similar conditions. Electron backscattered diffraction and scanning electron microscope were used for microstructural characterization and fractography. A comparative study with the feedstock revealed the effect of AFSD on hydrogen embrittlement and provided valuable insight into the role of AFSD processing in hydrogen embrittlement mitigation.