Norsk Hydro (Sweden)

Understanding and monitoring (iron) mineral dissolution in porous media is essential for predicting soil and groundwater geochemistry and guiding contaminant remediation efforts. The noninvasive geophysical technique, spectral induced polarization (SIP) measures the (changing) charge storage capacity at charged surfaces, linked with changes in geochemistry. Here, we present results from a flow-through column experiment, where we triggered Fe(II)-bearing mineral dissolution in a natural aquifer sand pack by infiltrating a 0.01 M HCl (pH = 2) solution. We combined breakthrough curve geochemical monitoring, with reactive transport modeling and simultaneous spatially and temporally resolved SIP measurements. The low pH front triggered mineral dissolution, and simultaneously, release of ionic species into solution as well as protonation and deprotonation of charged surfaces. These coupled parallel processes yielded distinct SIP signals. We detected a temporally variant and consistent V-shaped anomaly in the imaginary conductivity (σ″) signal. Despite the integrated contribution of coupled and parallel processes driving SIP signals, the joint interpretation with our reactive transport modeling results unequivocally linked the timing of the σ″ anomaly with the arrival and migration of the dissolution front. Our results highlight new ways to monitor subsurface geochemical reactions in real time and provide early warning tools for reactive transport applications.

Strains at the bottom of a large-scale experimental embankment dam were measured by fibre optics. The strains were measured in four sections, orthogonal to the dam axis. The fibre optic set up was operational after finalising the dam construction. The measurements were conducted continuously during the impoundment and later during the operation with an upstream water level of a maximum of 3.5 m. Based on the measurements, the post-construction behaviour of the dam was observed, indicating settlements. The foundation of the dam is inclined, which was captured by the measurements, with indications of more shear stresses developing at the downstream side. Variations of strains in the different dam zones were observed. The impoundment is causing most of the strain development in the dam. The strains develop further over time after the reservoir is at its maximum level, indicating a transient process is in place.

As hydrogen reduces the fatigue life of 100Cr6 bearing steel significantly, extensive research on the interaction of hydrogen with 100Cr6 is necessary. This study investigated the influence of rolling/sliding tribotesting performed on a micro-pitting-rig on the hydrogen absorption and trapping behaviour of 100Cr6 bearing steel. Thermal desorption mass spectrometry was used to compare the hydrogen desorption spectra of 100Cr6 samples after tribological tests and static heated oil-immersion tests to untested reference samples. The approach was chosen to further understand the influence of both microstructural deformation as well as steel-oil contact on the hydrogen absorption and trapping behaviour of 100Cr6. The tribological test showed a stable friction behaviour and mild wear which was dominated by local plastic deformation of surface asperities. Despite the mild wear, a change in de-trapping temperatures was found for tribotested samples compared to oil-immersed and untested reference samples. This finding indicates that even mild tribotesting conditions alter the hydrogen trapping behaviour of 100Cr6 bearing steel.

Abstract A global transition towards more sustainable, affordable and reliable energy systems is being stimulated by the Paris Agreement and the United Nation's 2030 Agenda for Sustainable Development. This poses a challenge for the corrosion industry, as building climate‐resilient energy systems and infrastructures brings with it a long‐term direction, so as a result the long‐term behaviour of structural materials (mainly metals and alloys) becomes a major prospect. With this in mind “Corrosion Challenges Towards a Sustainable Society” presents a series of cases showing the importance of corrosion protection of metals and alloys in the development of energy production to further understand the science of corrosion, and bring the need for research and the consequences of corrosion into public and political focus. This includes emphasis on the limitation of greenhouse gas emissions, on the lifetime of infrastructures, implants, cultural heritage artefacts, and a variety of other topics.

Present work demonstrates high speed friction stir welding (HSFSW) of light weight battery trays assembly in electric vehicle (EV). Despite of solid-state and green nature of FSW, it suffers from the relatively low welding speed. With the help of suitable tool design and machine tool parameters, we successfully achieved defect-free welds at high welding speed of 4.0 and 4.5 m/min. Good quality welds are produced in 3 mm thick AA6063-T6 extruded aluminium alloy at such a high welding speeds by implementing violent material mixing i.e., higher tool rotation speeds (3500–4500 rpm) and plunge force (8.5–10.5 kN). The HSFSW cross-section registered curious hardness profile of ‘U’ shape. HSFSW resulted softening of weld stir zone (∼60 HV) along with HAZ (∼50 HV). The highest joint efficiency of 72 % was found for the weld produced at 4.0 m/min and 3500 rpm.

Present work aims to achieve high welding speed during friction stir welding of lightweight battery trays in the electric vehicle industry. This study reports high-speed friction stir welding (HSFSW) up to 4.0 m min−1 in AA6063-T6 alloys. The defect-free HSFSW joints are produced by adopting aggressive material mixing, i.e. higher tool rotation and plunge force. HSFSW weld cross-section reported an unusual hardness profile of ‘U’ shape instead of ‘W’ shape in conventional FSW of AA6xxx alloys. HSFSW resulted softening of weld stir zone (∼60HV) along with HAZ (∼53HV) against the base material (BM) hardness of ∼90HV. The HSFSW at 4.0 m min−1 obtained good joint strength of 71% of the BM. Microstructure evolutions across the fractured weld cross-section are discussed using EBSD analysis.

Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solution annealing before a two-stage ageing process. Depending on the heat treatment procedure, strength or ductility can be enhanced, typically at the cost of the other. This study aims to determine a heat treatment procedure suitable for applications that require high ductility. Tensile tests of Inconel 718 processed by laser powder bed fusion additive manufacturing has been carried out on specimens subjected to different heat treatment procedures. The results show that solution annealing above 1010 °C followed by a two-stage ageing at 720 °C/8 h with furnace cooling to 620 °C/2 h and final holding at 620 °C/10 h, produce elongation at break of above 30% tested at room temperature and above 24% tested at 650 °C.