Effects of cathodic hydrogen charging on the mechanical properties and fracture behaviour of wire arc additively manufactured AA2319

The growing adoption of wire arc additive manufacturing (WAAM) requires an understanding of how WAAM-fabricated aluminium alloys respond to environmental factors that may degrade mechanical performance. This study investigates the effects of cathodic charging on the mechanical properties and fracture behaviour of WAAM AA2319 aluminium alloy. Cathodic charging was conducted in an electrolyte containing 3.5 wt.% NaCl and 3 g/L ammonium thiocyanate using different applied current densities. The resulting changes in mechanical performance were assessed through uniaxial tensile and Charpy impact toughness tests. The results demonstrate that cathodic charging led to a progressive reduction in ductility with increasing current density. Elongation decreased by up to approximately 45% relative to the uncharged condition, while ultimate tensile strength and yield strength were marginally affected. Charpy impact testing revealed a corresponding reduction in impact toughness of approximately 40% following hydrogen charging. Fractographic analysis showed a transition from ductile fracture dominated by microvoid coalescence in the uncharged material, to a mixed ductile–brittle fracture in hydrogen-charged specimens, characterised by shallow dimples and quasi-cleavage features. The observed changes in mechanical behaviour and fracture morphology suggest that cathodic charging promoted hydrogen-assisted mechanical degradation, with features consistent with hydrogen-enhanced localised plasticity (HELP) and hydrogen-enhanced decohesion (HEDE).