Malcolm António

Hydrogen embrittlement in welded joints is a critical integrity issue for hydrogen transport, storage, offshore, and structural applications because welding introduces microstructural heterogeneity, residual stresses, stress concentrators, and defect-susceptible regions. This review critically synthesizes published evidence on metallic welded joints across pipeline, structural, stainless, duplex/super duplex, Cr–Mo, nickel-based, titanium and aluminum alloys, with emphasis on weld metal, heat-affected zone and base-metal behavior under different hydrogen exposure and mechanical testing conditions. A structured literature survey links reported mechanical responses and damage locations to exposure, weld condition, and test configuration. The heat-affected zone is frequently implicated in ferritic steel welds, although weld-metal or base-metal control may occur depending on hydrogen-entry route, weld metallurgy, trapping behavior, geometry, constraint, residual stress, defects and test method. Apparent contradictions in the literature can therefore arise from differences in testing and exposure conditions. Tensile ductility loss identifies hydrogen sensitivity but does not independently establish fracture resistance or fatigue performance; heterogeneous datasets support conditional trends rather than universal rankings. Overall, hydrogen qualification should move from base-metal-centered assessment towards weld-region-centered evaluation. X52–X65 steels, 316L stainless steel and Alloy 625 emerge as candidates for distinct engineering roles, subject to qualification of the intended welded condition, while future work should prioritize service-representative, zone-resolved fatigue and fracture data to support reliable design, inspection and fitness-for-service assessment.

This study investigates the impact of low-temperature stress-relieving treatment on the fatigue life of AlSi10Mg components produced by Laser Powder Bed Fusion (L-PBF). The research focuses on a bicycle crank arm, comparing its performance in as-built and heat-treated conditions. The heat treatment involved stress-relieving at 250 °C for 2 h, followed by water quenching. The study found that the as-built condition exhibited a supersaturated Si cellular-dendritic microstructure, while the heat-treated condition showed coarsening of β-Mg₂Si phases and Si precipitates. This morphological change led to a decrease in hardness and an increase in ductility. Fatigue tests demonstrated that the heat-treated crank arms achieved the target of 100,000 cycles without failure, unlike the as-built samples, which failed prematurely. The fractography analysis identified surface porosity as the primary crack initiation site. The findings suggest that low-temperature stress-relieving treatment can enhance the fatigue performance of L-PBF AlSi10Mg components by reducing residual stresses and improving defect tolerance.