Bone aluminum accumulation in the current era / Acúmulo de alumínio no tecido ósseo na era atual

In the last few years, evidence from the Brazilian Registry of Bone Biopsy (REBRABO) has pointed out a high incidence of aluminum (Al) accumulation in the bones of patients with CKD under dialysis. This surprising finding does not appear to be merely a passive metal accumulation, as prospective data from REBRABO suggest that the presence of Al in bone may be independently associated with major adverse cardiovascular events. This information contrasts with the perception of epidemiologic control of this condition around the world. In this opinion paper, we discussed why the diagnosis of Al accumulation in bone is not reported in other parts of the world. We also discuss a range of possibilities to understand why bone Al accumulation still occurs, not as a classical syndrome with systemic signs of intoxication, as occurred it has in the past.

Nos últimos anos, evidências do Registro Brasileiro de Biópsia óssea (REBRABO) apontaram uma alta incidência de intoxicação por alumínio (Al) no tecido ósseo de pacientes com DRC em diálise. Essa surpreendente informação parece representar não apenas um acúmulo passivo deste metal, visto que dados prospectivos do REBRABO sugerem que a presença de Al no tecido ósseo pode estar independentemente relacionada a eventos cardiovasculares adversos maiores. Essas informações contrastam com a percepção mundial do controle epidemiológico dessa condição. Neste artigo de opinião, discutimos por que o diagnóstico de acúmulo ósseo de Al não é relatado em outras partes do mundo, e também discutimos uma gama de possibilidades para entender por que nós acreditamos que o acúmulo de Al no tecido ósseo ainda ocorre, não como se apresentava no passado, ou seja, como uma síndrome com sinais e sintomas sistêmicos de intoxicação.

Analysis of Immunobiological Properties of Recombinant Streptococcus pneumoniae Pneumolysin.

We compared the immunogenicity of recombinant S. pneumoniae pneumolysin (rPly) when administered with and without Al(OH)3 adjuvant, and evaluated the protective properties of recombinant protein in the active defense experiment. It was shown that double immunization with rPly+Al(OH)3 increases the levels of IgG antibodies in comparison with the control (p<0.01), while triple immunization results in a more significant increase in IgG antibody levels (p<0.001). Double immunization with rPly without Al(OH)3 does not induce a significant increase in antibody levels in comparison with the control, while triple immunization results in a slight but significant increase in antibody levels (p<0.05). The active defense test proved the protective activity of rPly against S. pneumoniae serotype 3 at intranasal infection.

The role of miRNA-21 and hypoxia inducible factor-1 in predicting post mortem interval in cardiac muscles of aluminum phosphide deaths.

BACKGROUND: The assessment of the postmortem interval (PMI) represents one of the major challenges in forensic pathology. Because of their stability, microRNAs, or miRNAs, are anticipated to be helpful in forensic research. OBJECTIVE: To see if estimation of PMI is possible using miRNA-21 and Hypoxia-inducible factor-1α (HIF-1α) expression levels in the heart samples from aluminum phosphide toxicity (Alpt). METHODS: This was a cross sectional study on 60 post-mortem samples (heart tissues) collected at different intervals during forensic autopsies. The two groups were allocated equally according to the cause of death into Group I (non-toxicated deaths, n = 30): Deaths caused by other than toxicity, and Group II (toxicated deaths, n = 30): Deaths due to Alpt. MDA (Malondialdehyde) and GSH (Glutathione), were measured in heart tissues using ELIZA. MiRNA- 21and HIF-1α expression levels were measured in heart tissues at different PMI using RT-Q PCR. ROC curve for detection of toxicated deaths using miRNA-21 and HIF was carried out. RESULTS: miRNA-21 and HIF-1α expression levels in Alp deaths were up regulated while GSH was downregulated with statistically significant difference. There was positive correlation between miRNA-21, HIF-1α and MDA with PMI while there was negative correlation between GSH and PMI in Alp deaths. In prediction of post mortem interval in Alp deaths miRNA-21 sensitivity and specificity were (75.9 %, 51.7 %, respectively) while HIF-1α sensitivity and specificity were 100 %. CONCLUSION: PMI can be calculated using the degree to which particular miRNA-21 and HIF-1α are expressed in the heart tissue. The combination of miRNA-21 with HIF-1α in post mortem estimation is precious indicators.

Synergistic integration of a rhodamine-labelled tripeptide into AIE-active fluorogenic probe: Enabling nanomolar detection of Al3+ ions through test strips, thin films, and Arduino-assisted optosensing platform.

Peptide-fluorophore conjugates (PFCs) have been expeditiously utilized for metal ion recognition owing to their distinctive characteristics. Selective detection and quantification of aluminum is essential to minimize health and environmental risks. Herein, we report the synthesis and characterization of a new chemoprobe with aggregation-induced emission characteristics by chemically conjugating rhodamine-B fluorophore with a tripeptide. The probe revealed ß-sheet secondary conformation in both solid and solution states, as confirmed by FT-IR, PXRD, and CD experiments. AIE characteristics of the probe in water-MeCN mixtures revealed the formation of spherically shaped nanoaggregates with an average size of 353 ± 7 nm, as confirmed by SEM, TEM, and DLS studies. The probe exhibited a large stokes shift (175 nm) and displayed selective colorimetric and fluorometric responses towards Al3+ ions with an extremely low detection limit (51 nm) and a fast response time (≤15 s). Comparative NMR studies confirmed the cleavage of spirolactam ring upon aluminum binding. The probe's practicality was enhanced through integration into test strips and thin films, allowing solid-phase detection of Al3+ ions. Furthermore, an RGB-Arduino enabled optosensing device has been developed to enable instant quantifiable analysis of aluminum concentrations in real-time conditions.

A profound study of damage behavior for Al 2024-T3 alloy worksheet produced by constrained groove pressing in the superior practical condition.

Constrained groove pressing (CGP) process is one of the most efficient and novel methods of severe plastic deformation to manufacture ultra-fine sheet metal. The present research work is related to the study of CGP process of 2024-T3 Aluminum alloy sheet. The empirical and numerical simulation of CGPed- specimens have been examined at both room and elevated temperatures. In order to simulate the constrained groove pressing process in Abaqus software, the Johnson-Cook material model has been employed. The geometrical variables of the CGP process include the teeth number, teeth angle, and sheet thickness, and the criterion for the superiority of the numerical test is the maximum reduction of two equivalent strain and equivalent force factors, simultaneously. To determine the weight's coefficients of the target factors and select the superior test, the Shannon's Entropy and Simple Additive Weighting (SAW) methods have been used, respectively. After validating the numerical findings, the variation of damage parameter, stress triaxiality and the equivalent plastic strain distribution in the superior practical condition have been evaluated in detail. Based on the Entropy-SAW hybrid technique, the weight's coefficients of equivalent strain and equivalent force target factors were computed to, in turn, 0.38 and 0.62. Also, the results revealed that the CGP process could not be performed at room temperature based on high damage evolution. But, at elevated temperature, the damage parameter (D) doesn't exceed 0.26. Also, the maximum stress triaxiality and equivalent plastic strain (PEEQ) at this process temperature reached to 0.5 and 0.1, respectively.

Hyperhidrosis and Neurofibromatosis Type 1: A Case Report.

In this report, we present the case of a 20-year-old male with childhood-onset hyperhidrosis affecting his fingers and palm flexor surfaces. Dermatological examination revealed café-au-lait macules, palm and sole involvement, and axillary freckling. A starch-iodine test confirmed localized sweating. Neuroimaging identified neurofibromatosis type 1 (NF1) with subcutaneous nodules and dural ectasia in the thoracic spine. The patient was diagnosed with hyperhidrosis and NF1 based on diagnostic criteria, and he responded well to 20% aluminum chloride for treatment of hyperhidrosis. This case represents a unique occurrence of hyperhidrosis with NF1 in Saudi Arabia. Comprehensive evaluation, including systemic assessment, radiology, and starch-iodine testing, aids in diagnosis and understanding of the underlying mechanisms of this disorder, which remains unexplained.

Small-molecule organic electrode materials on carbon-coated aluminum foil for high-performance sodium-ion batteries.

Organic molecular electrode materials are promising candidates in batteries. However, direct application of small molecule materials usually suffers from drastic capacity decay and inefficient utilization of active materials because of their high solubility in organic electrolytes and low electrical conductivity. Herein, a simple strategy is found to address the above issues through coating the small-molecule organic materials on a commercialized carbon-coated aluminum foil (CCAF) as the enhanced electrode. Both the experimental and calculation results confirm that the relatively rough carbon coating on the aluminum foil not only exhibits superior adsorption capacity of small-molecule organic electrode materials with a tight contact interface but also provides continuous electronic conduction channels for the facilitated charge transfer and accelerated reaction kinetics. In addition, the carbon coating also inhibits Al corrosion in electrochemical process. As a result, by using the tetrahydroxy quinone-fused aza-phenazine (THQAP) molecule as an example, the THQAP-CCAF electrode exhibits an excellent rate performance with a high capacity of 220 and 180 mAh g-1 at 0.1 and 2 A/g, respectively, and also a remarkable cyclability with a capacity retention of 77.3% even after 1700 cycles in sodium-ion batteries. These performances are much more superior than that of batteries with the THQAP on bare aluminum foil (THQAP-AF). This work provides a substantial step in the practical application of the small-molecule organic electrode materials for future sustainable batteries.

Epigenetic Mechanisms of Aluminum-Induced Neurotoxicity and Alzheimer's Disease: A Focus on Non-Coding RNAs.

Aluminum (Al) is known to induce neurotoxic effects, potentially contributing to Alzheimer's disease (AD) pathogenesis. Recent studies suggest that epigenetic modification may contribute to Al neurotoxicity, although the mechanisms are still debatable. Therefore, the objective of the present study was to summarize existing data on the involvement of epigenetic mechanisms in Al-induced neurotoxicity, especially AD-type pathology. Existing data demonstrate that Al exposure induces disruption in DNA methylation, histone modifications, and non-coding RNA expression in brains. Alterations in DNA methylation following Al exposure were shown to be mediated by changes in expression and activity of DNA methyltransferases (DNMTs) and ten-eleven translocation proteins (TETs). Al exposure was shown to reduce histone acetylation by up-regulating expression of histone deacetylases (HDACs) and impair histone methylation, ultimately contributing to down-regulation of brain-derived neurotrophic factor (BDNF) expression and activation of nuclear factor κB (NF-κB) signaling. Neurotoxic effects of Al exposure were also associated with aberrant expression of non-coding RNAs, especially microRNAs (miR). Al-induced patterns of miR expression were involved in development of AD-type pathology by increasing amyloid ß (Aß) production through up-regulation of Aß precursor protein (APP) and ß secretase (BACE1) expression (down-regulation of miR-29a/b, miR-101, miR-124, and Let-7c expression), increasing in neuroinflammation through NF-κB signaling (up-regulation of miR-9, miR-125b, miR-128, and 146a), as well as modulating other signaling pathways. Furthermore, reduced global DNA methylation, altered histone modification, and aberrant miRNA expression were associated with cognitive decline in Al-exposed subjects. However, further studies are required to evaluate the contribution of epigenetic mechanisms to Al-induced neurotoxicity and/or AD development.

Modulation of external and internal aluminum resistance by ALS3-dependent STAR1-mediated promotion of STOP1 degradation.

The ALMT1 transporter aids malate secretion, chelating Al3+ ions to form nontoxic Al-malate complexes, believed to exclude Al from the roots. However, the extent to which malate secreted by ALMT1 is solely used for the exclusion of Al3+ or can be reutilized by plant roots for internal Al tolerance remains uncertain. In our investigation, we explored the impact of malate secretion on both external and internal Al resistance in Arabidopsis thaliana. Additionally, we delved into the mechanism by which the tonoplast-localized bacterial-type ATP-binding cassette (ABC) transporter complex STAR1/ALS3 promotes the degradation of the Al resistance transcription factor STOP1 to regulate ALMT1 expression. Our study demonstrates that the level of secreted malate influences whether the Al-malate complex is excluded from the roots or transported into root cells. The nodulin 26-like intrinsic protein (NIP) subfamily members NIP1;1 and NIP1;2, located in the plasma membrane, coordinate with STAR1/ALS3 to facilitate Al-malate transport from root apoplasm to the symplasm and eventually to the vacuoles for the internal Al detoxification. ALS3-dependent STAR1 interacts with and promotes the degradation of STOP1, regulating malate exudation. Our findings demonstrate the dual roles of malate exudation in external Al exclusion and Al absorption for internal Al detoxification.

Dyotropic Rearrangement of an Iron-Aluminium Complex.

Ligand exchange processes at metal complexes underpin their reactivity and catalytic applications. While mechanisms of ligand exchange at single site complexes are well established, occurring through textbook associative, dissociative and interchange mechanisms, those involving heterometallic complexes are less well developed. Here we report the reactions of a well-defined Fe-Al hydride complex with exogeneous ligands (CO and CNR, R = Me, tBu, Xyl = 2,6-Me2C6H3). Based on DFT calculations we suggest that these reactions occur through a dyotropic rearrangement, this involves initial coordination of the exogenous ligand at Al followed by migration to Fe, with simultaneous migration of a hydride ligand from Fe to Al. Such processes are rare for heterometallic complexes. We study the bonding and mechanism of the dyotropic rearrangement through in-depth computational analysis (NBO, IBOs, CLMO analysis, QTAIM, NCIplot, IMGH), shedding new light on how the electronic structure of the heterometallic core responds to the migration of ligands between metal sites. The dyotropic rearrangement fundamentally changes the nature of the hydride ligands, exposing new nucleophilic reactivity as evidenced by insertion reactions with CO2, isocyanates, as well as isocyanides.

Electrolytic synthesis of γ-Al2O3 nanoparticle from aluminum scrap for enhanced methylene blue adsorption: experimental and RSM modeling.

The presence of methylene blue (MB) dye in wastewater has raised concern about human health and environmental ecology due to potential carcinogenic, and mutagenic effects. Therefore, this work aims to remove MB dye from wastewater using γ-Al2O3 nanoparticles synthesized from aluminum scrap via simple electrolytic method. The successful synthesis of the adsorbent was confirmed by a range of spectroscopy and microscopy techniques, including XRD, SEM, FTIR, and BET. The central composite design (CCD) of the response surface methodology (RSM) method was used to optimize the processing parameters such as solution pH, contact time, initial MB concentration, and adsorbent dose. The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of MB dye (R2 = 0.9862). The optimum condition for the maximum MB dye removal (98.91%) was achieved at solution pH of 8.298, initial MB concentration of 31.657 mg/L, adsorbent dose of 0.387 g/L, and contact time of 46.728 min. Nano-γ-Al2O3 was shown to have a good surface area of 59 mg2/g by BET analysis. The adsorption kinetics follows the pseudo-second-order model (R2 = 0.997). With a maximum adsorption capacity of 137.17 mg/g, the Langmuir isotherm model (R2 = 984) provides the best fit to the adsorption isotherm data, indicating a monolayer adsorption process. Furthermore, thermodynamic analysis demonstrated that the adsorption of MB dye was an endothermic and spontaneous process. The reusability study showed that γ-Al2O3 nano-adsorbent retained 85.08% of its original removal efficiency after five cycles. According to the findings of the study, MB dye molecules were taken up by γ-Al2O3 nano-adsorbent via hydrogen bond formation, Van der Waals interaction, and electrostatic attraction. Therefore, γ-Al2O3 nanoparticles can be used as a potentially eco-friendly and low-cost adsorbent for the removal of MB dye from aqueous solutions.

A bisalicylhydrazone based fluorescent probe for detecting Al3+ with high sensitivity and selectivity and imaging in living cells.

A bisalicylhydrazone based fluorescence probe, bisalicyladehyde benzoylhydrazone (BS-BH), has been designed to detect Al3+. It exhibited high sensitivity and selectivity towards Al3+ in methanol-water media in physiological condition. Large stokes shifts (∼122 nm) and over ∼1000-fold enhanced fluorescence intensity were observed, which was ascribed to the formation of the two relatively independent rigid extended π conjugated systems bridged by biphenyl group when binding with Al3+. A 1:2 binding ratio between BS-BH and Al3+ was shown by Job's plot. Based on the fluorescence titration data, the detection limit was down to 3.50 nM and the association constant was evaluated to be 1.12 × 109 M-2. The plausible fluorescence sensing mechanism of suppressed ESIPT, inhibited PET, activated CHEF and restricted C = N isomerization was confirmed by a variety of spectral experiments and DFT / TD-DFT calculations. The reversibility of recognition of Al3+ for probe BS-BH was validated by adding Na2-EDTA. In addition, the MTT assay showed the good biocompatibility of BS-BH and BS-BH could be used for imaging Al3+ in living cells.

Three in one: coordination-induced emission for inherent fluorescent Al-MOF synthesis combined with inner filter effect@aggregation-induced emission mechanisms for designing color tonality and ratiometric sensing platforms.

Three phenomena, namely coordination-induced emission (CIE), aggregation-induced emission (AIE), and inner filter effect (IFE), were incorporated into the design of a ratiometric and color tonality-based biosensor. Blue fluorescent Al-based metal-organic frameworks (FMIL-96) were prepared from non-emissive ligand and aluminum ions via CIE. Interestingly, the addition of tetracycline (TC) led to ratiometric detection and color tonality, as the blue emission at 380 nm was quenched (when excited at 350 nm) due to IFE, while the green-yellowish emission at 525 nm was enhanced due to AIE. Based on that, an ultra-sensitive visual-based color tonality mode with smartphone assistance was developed for detection of TC. The sensor exhibited a linear relationship within a broad range of 2.0 to 85.0 µM TC with a detection limit of 68.0 nM. TC in milk samples was quantified with high accuracy and precision. This integration of smartphone and visual fluorescence in solution is accurate, reliable, cost-effective, and time-saving, providing an alternative strategy for the semi-quantitative determination of TC on-site.

Evaluation of the Protective Effects of Lugol's Solution in Rats Poisoned with Aluminum Phosphide (Rice Tablets).

Aluminum phosphide (AlP) is the main component of rice tablets (a pesticide), which produces phosphine gas (PH3) when exposed to stomach acid. The most important symptoms of PH3 toxicity include, lethargy, tachycardia, hypotension, and cardiac shock. It was shown that Iodine can chemically react with PH3, and the purpose of this study is to investigate the protective effects of Lugol solution in poisoning with rice tablets. Five doses (12, 15, 21, 23, and 25 mg/kg) of AlP were selected, for calculating its lethal dose (LD50). Then, the rats were divided into 4 groups: AlP, Lugol, AlP + Lugol, and Almond oil (as a control). After 4 h, the blood pressure and electrocardiogram (ECG) were recorded, and blood samples were obtained for biochemical tests, then liver, lung, kidney, heart, and brain tissues were removed for histopathological examination. The results of the blood pressure showed no significant changes (P > 0.05). In ECG, the PR interval showed a significant decrease in the AlP + Lugol group (P < 0.05). In biochemical tests, LDH, Ca2+, Creatinine, ALP, Mg2+, and K+ represented significant decreases in AlP + Lugol compared to the AlP group (P < 0.05). Also, the administration of Lugol's solution to AlP-poisoned rats resulted in a significant decrease in malondialdehyde levels and a significant increase in catalase activity (P < 0.05). Histopathological evaluation indicates that Lugol improves changes in the lungs, kidneys, brain, and heart. Our results showed that the Lugol solution could reduce tissue damage and oxidative stress in AlP-poisoned rats. We assume that the positive effects of Lugol on pulmonary and cardiac tissues are due to its ability to react directly with PH3.

Aluminum causes irreversible damage to the development of hippocampal neurons by regulating m6A RNA methylation.

The underlying mechanism of the aluminum (Al) on neurotoxicity remains unclear. We explored whether the impairment of hippocampal neurons induced by developmental Al exposure was associated with the m6A RNA modification in mice. In this study, the pregnant female mice were administered 4 mg/mL aluminum-lactate from gestational day (GD) 6 to postnatal day (PND) 21. On PND 21, 10 offsprings per group were euthanized by exsanguination from the abdominal aorta after deep anesthetization. The other offsprings which treated with aluminum-lactate on maternal generation were divided into two groups and given 0 (PND60a) and 4 mg/mL (PND60b) aluminum-lactate in their drinking water until PND 60. Significant neuronal injuries of hippocampus as well as a reduction in the m6A RNA modification and the expression of methylase were observed at PND 21 and PND 60a mice. The results indicated that Al-induced developmental neurotoxicity could persist into adulthood despite no sustained Al accumulation. m6A RNA modification had a crucial role in developmental neurotoxicity induced by Al. In addition, Al exposure during the embryonic to adult stages can cause more severe nerve damage and decline of m6A RNA modification. Collectively, these results suggest that the mechanism underlying Al-induced neurotoxicity appears to involve m6A RNA modification.

Construction of Fe Nanoparticles Interfacial Layer on Micron Al Surface: Boosting the Efficient Energy Release of High-Energy DAP-4 as a Gradient Catalyst.

The high-energy (H2dabco)[NH4(ClO4)3] (DAP-4) with excellent energetic performance attracts wide attention from researchers. The investigation of its interaction with the Aluminum (Al) is of great importance. However, the higher ignition threshold of DAP-4 and the dense oxide layer (Al2O3) of Al severely limit the energy release efficiency of Al/DAP-4. In this study, a new idea to is first proposed to improve and adjust the thermal decomposition and combustion performance of Al/DAP-4 by constructing a highly dispersed iron (Fe) nanoparticle interfacial layer. It acts as a gradient catalyst to promote the thermal decomposition and combustion of DAP-4 and Al, and it also act as an oxygen transport channel to promote the contact and reaction of oxidizing gases with the internal reactive Al powder. It reduces the thermal decomposition temperature of Al@Fe-3/DAP-4 from 386.30 °C (Al/DAP-4) to 349.48 °C and leads to the vigorous combustion. Theoretical calculations show that Fe nanoparticle interfacial layer can facilitate the transport of oxygen through the established oxygen transport channels, and it can also significantly improve the energetic properties of Al@Fe-3/DAP-4 composites. In conclusion, the new approach is proposed to improve the performance of metal fuel/oxidizer composites by constructing interfacial layers, which is expected to promote their practical applications.

The stem cell niche transcription factor ETHYLENE RESPONSE FACTOR 115 participates in aluminum-induced terminal differentiation in Arabidopsis roots.

Aluminum-dependent stoppage of root growth requires the DNA damage response (DDR) pathway including the p53-like transcription factor SUPPRESSOR OF GAMMA RADIATION 1 (SOG1), which promotes terminal differentiation of the root tip in response to Al dependent cell death. Transcriptomic analyses identified Al-induced SOG1-regulated targets as candidate mediators of this growth arrest. Analysis of these factors either as loss-of-function mutants or by overexpression in the als3-1 background shows ERF115, which is a key transcription factor that in other scenarios is rate-limiting for damaged stem cell replenishment, instead participates in transition from an actively growing root to one that has terminally differentiated in response to Al toxicity. This is supported by a loss-of-function erf115 mutant raising the threshold of Al required to promote terminal differentiation of Al hypersensitive als3-1. Consistent with its key role in stoppage of root growth, a putative ERF115 barley ortholog is also upregulated following Al exposure, suggesting a conserved role for this ATR-dependent pathway in Al response. In contrast to other DNA damage agents, these results show that ERF115 and likely related family members are important determinants of terminal differentiation of the root tip following Al exposure and central outputs of the SOG1-mediated pathway in Al response.

Construction of V2O5@MXene Cathodes toward a High Specific Capacity Aqueous Aluminum-Ion Battery.

Aqueous aluminum-ion batteries (AAIBs) are considered a strong candidate for the new generation of energy storage devices. The lack of suitable cathode materials has been a bottleneck factor hindering the future development of AAIBs. In this work, we design and construct a highly effective cathode with dual morphologies. Two-dimensional (2D) layered MXene materials possessed good conductivity and hydrophilicity, which are used as the substrates to deposit rod-shaped vanadium oxides (V2O5) to form a three-dimensional (3D) cathode. The cathode design provides a strong boost for the rapid electrochemical activities of rod-shaped V2O5 by embedding/extracting both protons (H+) and aluminum-ion (Al3+). As a result, the V2O5@MXene cathode based AAIB delivers an ultrahigh initial specific capacity of 626 mAh/g at 0.1 A/g with a stable cycle performance up to 100 cycles. This work is a breakthrough for the development of cathode materials for AAIBs.

The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance.

The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near "in situ" structure around the exit hole, an "emergency stop" followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism.

Wire Arc Additive Manufacturing of Aluminum Foams Using TiH2-Laced Welding Wires.

Composite materials made from aluminum foam are increasingly used in aerospace and automotive industries due to their low density, high energy absorption capacity, and corrosion resistance. Additive manufacturing processes offer several advantages over conventional manufacturing methods, such as the ability to produce significantly more geometrically complex components without the need for expensive tooling. Direct Energy Deposition processes like Wire Arc Additive Manufacturing (WAAM) enable the additive production of near-net-shape components at high build rates. This paper presents a technology for producing aluminum foam structures using WAAM. This paper's focus is on the development of welding wires that are mixed with a foaming agent (TiH2) and produce a foamed weld metal as well as their processing using MIG welding technology.