Friction self-piercing riveting (FSPR) is a unique hybrid joining technique that combines the advantages of mechanical interlocking, frictional heat, and solid-state joining (if metallurgically compatible) to produce crack free joints in high strength and/or low-ductility alloys at room temperature. In the current study, Al-7055 sheets were joined using FSPR for lightweight automotive applications and significant microhardness variations were observed across the joint cross-section. A detailed microstructural characterization at multiple length scales was carried out using advanced electron microscopy and X-ray scattering techniques to provide a fundamental understanding of the process-structure-property relationships. The relative contributions of microstructural characteristics at various length scales (i.e., grain size, dislocation density, solute concentration, precipitate nature) to strengthening were estimated using existent formulations (i.e., Hall-Petch, Taylor, precipitate bypass/shear equations) and correlated to the observed microhardness values across different regions. Small-angle X-ray scattering and scanning transmission electron microscopy revealed significant changes in the size and volume fraction of precipitate species, i.e., GP-I Zones, eta ', and Mg/Zn solute co-clusters, depending on the process region. It was observed that the dissolution of the small eta '/GP-I zones (T similar to 150-200 degrees C) in the heat-affected zone were the key reason for the hardness drop. Further, it was shown that solid-solution, dislocation, grain size and solute co-cluster strengthening played a key role in the thermo-mechanically affected zone and grain-refined zone (GRZ). Finally, these observations were leveraged along with the Zener-Holloman relationship and grain size in the GRZ to estimate the peak joining temperature of the GRZ (similar to 350 degrees C) near the steel rivet.

Liquid metal-based divertor concepts have promising attributes for application in fusion reactors. Liquid tin is being considered as one of those liquid metals due to its excellent thermophysical properties. However, tin is extremely corrosive to steels at elevated temperatures, and the coupled effects of corrosion with neutron irradiation for application in fusion reactors have not been quantified. Researchers at Oak Ridge National Laboratory (ORNL) have designed and irradiated a series of capsules in the High Flux Isotope Reactor (HFIR) to help address gaps in the literature with respect to coupled corrosion and neutron irradiation effects. The capsules are filled with solid tin designed to melt due to the gamma heating in HFIR and allow interaction with the specimens. The capsules contain a SiC thermometer for post-irradiation temperature verification. Five capsules were irradiated in HFIR for 10.5 days, accumulating 0.93 dpa in the FeCrAl specimens. Post-irradiation temperature verification was performed on the SiC thermometers, and temperatures were observed to be higher than what was expected from thermal models. An explanation for the model underprediction is given herein. The capsules described within this article are the first to irradiate liquid metal within the HFIR flux trap and demonstrated the safety basis for continued liquid coolant studies in HFIR.

Magnesium (Mg) alloys are appealing for automotive lightweighting owing to their high specific strength. However, their susceptibility to corrosion in harsh environments remains a major challenge. Conventional industrial pre-treatment coatings, including zinc phosphate, chromate conversion, and non-chromate conversion, often exhibit discontinuities and microcracks, leading to localized corrosion near fasteners and parting lines. This study investigates cold-sprayed zinc (Zn) coatings as a novel pre-treatment alternative for high-pressure die cast (HPDC) AZ91 Mg alloys, demonstrating significant improvements in wear and corrosion performance. Cold spray produces uniform and robust coatings, reducing wear rate by over 50

Two Al-Ce-Ni cast alloys, and an Al-Cu-Ce cast alloy, as candidate wet storage materials for spent nuclear fuels, were tested in 0.23 wt% H3BO3 solution to assess the alloy corrosion resistance. Electrochemical and gravimetric corrosion data suggest that the three Al alloys are unlikely to undergo any severe corrosion in dilute H3BO3 at or below 50 degrees C. Post-exposure characterization of the three Al alloys, including scanning and transmission electron microscopy and electron dispersive spectroscopy, revealed a corrosion product layer, mostly Al2O3, on the exposed surface and local penetration of oxygen into the alloy matrix. The degree of oxide layer growth and oxygen penetration is greater at 80 degrees C than the temperature at/below 50 degrees C. The Al-Cu-Ce alloy is considered less corrosion resistant than the other two alloys studied.

Uranium mononitride (UN) and alumina forming austenitic (AFA) stainless steel are a potential fuel-cladding combination for the lead-cooled fast reactor (LFR). Chemical compatibility between UN and AFA steel needs to be verified before implementation in a nuclear reactor. Diffusion couple experiments at 823 K and 1023 K were conducted for nonirradiated UN samples in contact with as-cast (no thermally grown Al2O3) and preoxidized (with thermally grown Al2O3) AFA for 500 and 1000 h in an inert environment. Preoxidized AFA exhibited little to no interaction with all UN samples tested at both 823 K and 1023 K, displaying the stability and capability of the Al2O3 layer to prevent chemical interaction and inter-diffusion with UN. Chemical interaction occurs between UN and as-cast AFA. At 1023 K, an aluminum and nitrogen rich phase (likely AlN) formed along the interface of as-cast AFA and UN samples. At 823 K the AlN phase was not prominently observed due to the reduced diffusivity of aluminum through AFA. The aluminum and nitrogen-enriched phase was also observed in a high temperature pressure-assisted test sample of UN and as-cast AFA thermally treated at 1373 K. In UN samples doped with a low weight percent of UO2 (< 3 wt%), AlN was not detected along the interface at either temperatures, and an Al2O3 layer likely formed along the interface and prevented further chemical interaction between UN and as-cast AFA.

High-pressure die cast (HPDC) AZ91 magnesium alloy is widely used in automotive components such as transmission housings and brackets for its excellent strength-to-weight ratio. Zinc-based cold spray coatings can be applied selectively to vulnerable areas to enhance corrosion resistance, minimize galvanic coupling with dissimilar metals, and eliminate the need for full-surface oxide coatings, making the process more efficient and targeted. A comprehensive evaluation of 16 combinations of nitrogen carrier gas temperatures and pressures led to the identification of an optimal range of process parameters, yielding Zn coatings with porosity < 0.5 % by area, wear rates reduced by a factor of two compared to uncoated AZ91, and adhesion strengths up to 35 MPa. The enhanced mechanical performance of the coating is attributed to the low porosity and the formation of a metallurgical bond at the coating-substrate interface. Corrosion studies using macroscale potentio-dynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) revealed a significant decrease in corrosion rate and a shift to more noble corrosion potentials (ZCP) for coated substrates. Furthermore, the Zn cold-sprayed samples exhibited significantly lower corrosion-induced evolved hydrogen content compared to the base AZ91 substrate and AZ91 coated with industrial coatings, demonstrating that the Zn layer effectively protects the substrate from the corrosive environment. Overall, cold spray Zn coatings significantly improve the mechanical and corrosion performance of AZ91 Mg alloys, addressing key material challenges and enabling their broader use in automotive applications. (c) 2025 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Iron based electrocoagulation (Fe-EC) is a promising contaminant removal technology based on electrochemical dissolution of iron from steel electrodes; however, the Fe-EC performance declines over extended operation associated with fouling layer formation. In this study, we characterized the fouling layer growth in a continuous-flow EC reactor for silica and hardness removal from secondary effluent of wastewater. The fouling layer exhibited a passivating effect, requiring a higher anode potential to maintain the desired electrical current, thus significantly decreasing Faradaic and pollutant removal efficiencies. To better understand the evolution and composition of the passivation layer, we conducted time-resolved microscopy, X-ray spectroscopy, and electrochemical analysis to obtain critical insights into the structure, morphology, and elemental composition of the fouling layer at different stages of formation. Experimental observations indicated that an initial thin, porous iron oxide layer formed on the anode surface. During extended operation, this oxide layer thickened to a dense, over 100-µm black iron oxide layer containing magnetite due to limited oxygen availability near the surface where iron ions were released. To address the challenge posed by the fouling layer, polarity reversal was applied to break up the fouling layer and restore anode reactivity, resulting in recovering Faradaic and pollutant removal efficiencies. The mechanism responsible for this improvement could be associated with the evolution of gas at the cathode surface after electrode reversal, which effectively removed the fouling layer. This work not only provides a deeper understanding of fouling-layer formation in Fe-EC, but also presents a practical approach to maintain the reactivity of the electrodes and optimize the effectiveness of Fe-EC systems.

A flowing Sn thermal convection loop (TCL) experiment was conducted in FeCrAlMo (Kanthal alloy APMT) tubing for 1000 h with a peak temperature of 400 °C. Oxide dispersion strengthened (ODS) Fe-(10–12)Cr-6Al and APMT specimens were exposed and all were pre-oxidized to form an external alumina scale. Unlike static exposures at 400° and 500 °C where pre-oxidation prevented dissolution, large mass losses were observed in the TCL hot leg after the specimens were cleaned in Li. The observed pitting suggests that localized failure of the pre-formed alumina surface oxide caused significant metal loss. Specimen mass gains were not observed on the cold leg implying that mass transfer did not occur and the small levels of Fe and Cr in the Sn after the experiment implies that Sn-rich phases may have formed. Post exposure room temperature tensile testing showed limited impact of the Sn exposure on the 12Cr ODS FeCrAl alloy, comparable to a 1000 h anneal in Ar at 400 °C. These results suggest that pre-oxidation is not sufficient to protect FeCrAl alloys in contact with flowing liquid Sn at 350°-400 °C.

A unique corrosion barrier layer, formed by thermal CO2 treatment with LiNO3 on AZ91D, was characterized to reveal the chemical species and their spatial distribution using the combination of scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS) techniques. Two distinct and spatially segregated phases were identified as Li compound(s) with MgCO3 and MgO in the surface barrier layer. Based on the characterization results, it is presumed that the reaction of Mg oxide/hydroxide with LiNO3 and CO2 occurred preferentially in some local areas where Li compound(s) with MgCO3 were present, but the unreacted areas contained MgO in the surface barrier layer.

High Pressure Die Cast (HPDC) Al alloys are of interest as automotive structural materials. Owing to the unique processing conditions, HPDC Al alloys may exhibit distinct microstructures compared to other cast automotive Al alloys. In this work, we are evaluating corrosion behavior of several HDPC Al alloys with varied chemical compositions in comparison with non-HPDC commercial Al cast alloy(s) using electrochemical impedance and polarization techniques, and long-term exposure sample characterization in typical 3.5 wt.% NaCl with and without HCl addition to lower pH. A lower pH NaCl solution is used to increase the frequency of corrosion attack growth for collection of statistical corrosion depth data. The key results will be discussed to allow semi-quantitative comparison of HPDC Al alloy resistance against corrosion initiation and growth.

Iron electrocoagulation (Fe-EC) performance often declines with time, producing lower contaminant removal efficiencies and higher energy requirements due to formation of a fouling layer on the electrodes. Here, we investigate the formation of the fouling layer and the effectiveness of polarity reversal to restore the Fe-EC performance. A thin, porous iron oxide layer initially forms on the anode, thickening into a dense, over 150-mu m thick crystalline layer after extended operation. This fouling layer restricts dissolution and diffusion of Fe ions into the bulk solution, thus increasing the anode potential required to maintain a desired electrical current and decreasing Faradaic efficiency. Polarity reversal applied when performance decline is observed effectively removes the fouling layer, thereby restoring Faradaic and contaminant removal efficiencies and decreasing energy consumption. Our findings suggest that gas generation at the cathode surface after polarity reversal causes removal of the fouling layer. This study enhances the current understanding of fouling-layer formation in Fe-EC and offers a practical approach, involving polarity reversal, to maintain electrode reactivity and optimal Fe-EC performance.

As a corrosion barrier layer, open-air plasma-assisted organosilicon coating was applied on AZ91D Mg alloy. Organosilicon-coated AZ91D samples, prepared from two different plasma coating processes, were used for corrosion evaluation based on multistep electrochemical and H 2 collection measurements in 3.5 wt% sodium chloride (NaCl) solution. Some coated AZ91D samples were characterized with and without corrosion exposure in NaCl solution using electron microscopies and X-ray chemical analysis techniques. The results indicate that the organosilicon coatings from open-air plasma processes are effective to delay the initiation of corrosion attack and also reduce the corrosion rate for AZ91D substrate. The corrosion attack was considered to develop after permeation of NaCl solution through the coating layer.

Polyoxometalates (POMs) are of great interest to the scientific community, and their reduction and nucleation have been well-established by multi-step techniques. The present study develops an electrochemical approach for simultaneous reduction and nucleation of polyoxometalate-containing solids. Herein we report crystal growth of reduced Preyssler polyoxotungstate-based (anionic formula [NaP5W30O110]14-) new crystalline solids made of Preyssler anions interlinked by Co2+ and Ni2+ ions. Crystal nucleation and in situ reduction were achieved at room temperature using a two silver wire electrode setup in various aqueous solutions under constant applied potentials. The POM material was deposited on the cathode, and its structure was characterized by X-ray diffraction techniques. The primary structure type observed involves POMs decorated by disordered Co2+/Ni2+ octahedra and fused into 1-D pillars by additional Co2+/Ni2+ octahedra. A secondary phase was observed in the Ni-based reactions, where reduced Preyssler anions are decorated by Ni4O4 cubane-like units. To understand the electrochemical process, polarization curves of the electrolyte solutions are presented, suggesting an applied potential best suited for crystal growth. The work highlights the effectiveness of an electrochemical pathway where nucleation and simultaneous reduction of POMs can make novel reduced POM solids.

The major technical hurdles for lightweight multi-material vehicles lie in joining and corrosion, particularly galvanic corrosion of dissimilar material joints. In this study, the friction self-piercing rivet (F-SPR) process was utilized to spot join carbon fiber reinforced polymer (CFRP) to AZ31B Mg alloy at a coupon scale. After fabricating the dissimilar joint samples, a unique corrosion exposure test was performed to investigate galvanic corrosion of AZ31B at the joint in 0.1 M NaCl solution. A novel oxide self-formation technique was employed on alumina forming austenitic (AFA) alloy to electrically insulate the rivet/multi-material interfaces for mitigating galvanic coupling effect in the dissimilar joint. Advanced characterization and electrochemical evaluation techniques were employed to study corrosion behaviors of oxide layer formed AFA alloy. The corrosion volume assessment of AZ31B at the joint revealed that the surface oxide layer formed on AFA alloy rivets significantly reduced galvanic corrosion compared to both the untreated AFA alloy and carbon steel rivets (control).

Mg alloy structural parts are of high interest to realize lightweight automobiles. However, corrosion susceptibility of Mg is one of the key technical challenges for the application of Mg alloys as vehicle parts. In this work, open-air plasma assisted organosilicon coating was deposited on AM60 Mg alloy as corrosion barrier using different deposition processes. This deposition process can minimize use of wet chemicals and be installed to existing industrial plasma devices. Corrosion evaluation of uncoated and organosilicon coated AM60 samples was conducted using electrochemical impedance spectroscopy, polarization and hydrogen collection measurements in 3.5% NaCl solution at room temperature. Post-immersion AM60 samples were characterized in comparison to unexposed AM60 samples using SEM, STEM and EDS to investigate progress of corrosion attack in uncoated and organosilicon coated surface conditions. According to corrosion evaluation, organosilicon coating provides corrosion protection for AM60 substrates in the initial stage. Long-term immersion results are currently under investigation.

Corrosion behavior of cast Al-Cu-Mn-Zr (ACMZ) and RR350 alloys was compared to a cast 319 alloy in 3.5 wt.% NaCl. After 168 h immersion, ACMZ and RR350 alloys suffered from preferential attack adjacent to intermetallic particles decorated at grain boundaries while the attack in 319 occurred in eutectic Al-Si dendritic boundaries. Electrochemical data allowed semiquantitative comparison of alloy resistance to corrosion initiation, and ACMZ type alloys, including RR350 and three alloys with higher Cu, were considered more resistant than 319 due to the absence of deleterious Si particles. In case of 319, such Si particles presumably drove higher micro-galvanic influence to initiate and sustain Al corrosion. With lower susceptibility to corrosion initiation, ACMZ alloys should exhibit higher or at minimum similar resistance compared to cast 319.

The formation of Mg–Li–C–O barrier layer on AZ91D Mg alloy using LiNO3-assisted thermal CO2 treatment provides a pathway to utilize excessive CO2 for corrosion protection of AZ91D.

To evaluate the liquid metal embrittlement (LME) susceptibility of F82H, a reduced activation ferriticmartensitic (RAFM) steel, a testing procedure using hollow cylindrical tensile specimens was used. Tensile tests are compared between specimens filled with argon and lithium at 200 degrees C. To validate the procedure, initial testing was performed on type 4340 steel, which is well-known to exhibit LME. Compared to 4340 steel, F82H only showed minor effects of Li exposure, including pre-testing exposures with Li at 400 degrees C for 1 hand 500 degrees C for 500 h. Furthermore, changing the strain rate or tensile test temperature also did not show significant embrittlement.

Previous studies demonstrated the corrosion susceptibility of advanced neutron absorber (ANA) Ni-Cr-Mo-Gd in a seawater environment but remained inconclusive. In this paper, scanning electron microscopy was employed to identify the corrosion phase in Ni-Cr-Mo-Gd, and computational thermodynamic simulation was used to study phase corrosion potentials. Results showed that the Ni5Gd second phase, distributed along FCC grain boundaries in Ni-Cr-Mo-Gd, has lower corrosion potential than the substrate. Furthermore, heat treatment and alloy chemistry adjustment would not ameliorate the ANA corrosion susceptibility. Isolating the Ni5Gd from the corrosion medium through advanced manufacturing is a viable way to improve the ANA corrosion resistance.