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.

Realization of Extremely High-Gain and Low-Power in nMOS Inverter Based on Monolayer WS2 Transistor Operating in Subthreshold Regime.

In this work, we report an n-type metal-oxide-semiconductor (nMOS) inverter using chemical vapor deposition (CVD)-grown monolayer WS2 field-effect transistors (FETs). Our large-area CVD-grown monolayer WS2 FETs exhibit outstanding electrical properties including a high on/off ratio, small subthreshold swing, and excellent drain-induced barrier lowering. These are achieved by n-type doping using AlOx/Al2O3 and a double-gate structure employing high-k dielectric HfO2. Due to the superior subthreshold characteristics, monolayer WS2 FETs show high transconductance and high output resistance in the subthreshold regime, resulting in significantly higher intrinsic gain compared to conventional Si MOSFETs. Therefore, we successfully realize subthreshold operating monolayer WS2 nMOS inverters with extremely high gains of 564 and 2056 at supply voltage (VDD) of 1 and 2 V, respectively, and low power consumption of ∼2.3 pW·µm-1 at VDD = 1 V. In addition, the monolayer WS2 nMOS inverter is further expanded to the demonstration of logic circuits such as AND, OR, NAND, NOR logic gates, and SRAM. These findings suggest the potential of monolayer WS2 for high-gain and low-power logic circuits and validate the practical application in large areas.

Rapid Fabrication of Antilunar Dust Aluminum Surface by Nanosecond Laser Etching.

Although a dust-repellent surface is desirable for lunar exploration missions, its fabrication process is complicated and time-consuming. Herein, we report a simple and fast method to fabricate a lunar dust-repellent surface by texturing on an Al substrate via nanosecond laser etching. The laser-induced photothermal effect can rapidly create hierarchical papillary structures on 25 × 25 mm Al substrates (within 30 s). Both atomic force microscopy (AFM) and in situ scanning electron microscopy (SEM) reveal that such structures enable a reduced contact area between the Al substrate and lunar dust and thus reduced adhesion. The reduced dust adhesion force of Al substrates facilitates improving their antidust performance. By optimizing processing parameters, the Al substrate etched with a laser scanning spacing of 80 µm exhibits a lower dust adhesion force (9.58 nN) due to the smallest contact area with dust. Accordingly, its static antilunar dust performance (dust coverage of 1.95%) is significantly improved compared to the pristine Al substrate (dust coverage of 12.98%). Besides, the accumulated dust on the laser-etched Al substrates with low surface adhesion force is easily cleaned up by flipping and gravity (the dust residual rates are less than 17%). The Al substrate with excellent antidust ability presents good potential for lunar exploration missions.

Evaluation of fluoride emissions and pollution from an electrolytic aluminum plant located in Yunnan province.

The monitoring and evaluation of fluoride pollution are essentially important to make sure that concentrations do not exceed threshold limit, especially for surrounding atmosphere and soil, which are located close to the emission source. This study aimed to describe the atmospheric HF and edaphic fluoride distribution from an electrolytic aluminum plant located in Yunnan province, on which the effects of meteorological conditions, time, and topography were explored. Meanwhile, six types of solid waste genereted from different electrolytic aluminum process nodes were characterized to analyze the fluoride content and formation characteristics. The results showed that fluoride in solid waste mainly existed in the form of Na3AlF6, AlF3, CaF2, and SiF4. Spent electrolytes, carbon residue, and workshop dust are critical contributors to fluoride emissions in the primary aluminum production process, and the fluorine content is 17.14 %, 33.30 %, and 31.34 %, respectively. Unorganized emissions from electrolytic aluminum plants and solid waste generation are the primary sources of fluoride in the environment, among which the edaphic fluoride content increases most at the sampling sites S1 and S7. In addition, the atmospheric HF concentration showed significant correlations with wind speed, varying wildly from March to September, with daily average and hourly maximum HF concentrations of 4.32 µg/m3 and 9.0 µg/m3, respectively. The results of the study are crucial for mitigating fluorine pollution in the electrolytic aluminum industry.

Vascular plants and biocrusts ameliorate soil properties serving to increase the stability of the Great Wall of China.

The Great Wall, as a World Heritage Site, is constructed with rammed earth and is currently facing the threat of erosion from wind and rain. Vascular plants and biocrusts are the main coverings of the Great Wall, and their role in mitigating soil erosion has attracted increased amounts of attention; however, the understanding of their underlying mechanisms is limited. Here, we conducted an extensive survey of vascular plants, biocrusts, soil properties (soil organic and inorganic binding materials, aggregates, and texture), soil aggregate stability, and soil erodibility at the top of the Great Wall in four different defensive zones in Northwest China. Vascular plants covered 13.6 % to 63.9 % of the tops of the Great Wall, and their rich diversity was mainly derived from perennial herbs. Moss, lichen, and cyanobacterial crusts collectively covered 36.3 % to 67.8 % of the top of the Great Wall. Redundancy analysis and structural equation modeling revealed that the synergistic effects of vascular plants and biocrusts enhanced soil aggregation stability (including geometric mean diameter, GMD; water-stable macroaggregate content, R) by increasing the accumulation of soil organic carbon (SOC), amorphous iron oxide (Feo), and amorphous alumina (Alo) and promoting the formation of macroaggregates (ASD>0.25 mm) and microaggregates (ASD0.053-0.25 mm). Furthermore, soil erodibility was primarily influenced negatively by the synergistic promotion of SOC accumulation by vascular plants and biocrusts and positively by the reduction in soil sand (PSD>0.05 mm) content by biocrusts. Our work highlights the mechanisms and importance of vascular plants and biocrusts as natural covers for altering the intrinsic properties of soil for the protection of the Great Wall. These findings provide reliable theoretical support for the protection of the Great Wall from erosion by vascular plants and biocrusts and offer new insights for the conservation of global earthen sites and similar wall habitats.

Effect of phosphoric acid etching and blasting with aluminum oxide on the enamel topography and adhesion of resin composite to intact or abraded enamel.

OBJECTIVES: To evaluate the effects of the phosphoric acid (PA) etching, self-etching technique (SE) and blasting with Al2O3 particles (BL) on the bonding of a dental adhesive to intact (INT) or abraded (ABR) enamel. METHODS: Enamel surfaces were treated as follows: 1- ABR-PA: INT was abraded with SiC paper and etched with PA (20 s) before Clearfil Universal Bond Quick adhesive application; 2- ABR-SE: ABR was SiC and adhesive applied in SE mode; 3- INT-PA: INT was etched with PA and adhesive applied; 4- INT-SE: the adhesive (SE mode) was applied to INT; 5- INT-BL: INT was BL and the adhesive was applied (SE mode), and 6- INT-BA: INT was BL, etched with PA and adhesive applied (SE mode). The enamel surface treated was examined with scanning electron microscopy (SEM) (n = 3) and Al2O3 particles were characterized using SEM and EDX. The enamel bond strength was measured by microtensile test (24 h and 1 year) (n = 8) and the morphology of enamel-adhesive interfaces were analyzed by SEM (n = 3). Bond strength data were analyzed by two-way ANOVA and Tukey's test (α = 0.05). RESULTS: Al2O3 particles had an irregular shape, their length varied (50-20 µm) and the perimeter mean was 38.8 µm. The enamel morphology significantly influenced the enamel bond strength. ABR-PA, INT-BL, and INT-BA provided greater and stable enamel-dentin interaction and bond strength. SIGNIFICANCE: The enamel morphology significantly influenced the enamel bond strength. Using the adhesive in etch-and-rinse mode, enamel must be abraded before etching and must be Al2O3-blasted when used in SE mode.

Synthesis and preclinical evaluation of [18F]AlF-NODA-MP-C6-CTHRSSVVC as a PET tracer for CD163-positive tumor-infiltrating macrophages.

Positron emission tomography (PET) can provide information about tumor-associated macrophage (TAM) infiltration, as long as a suitable tracer is available. This study aimed to evaluate the radiolabeled peptide [18F]AlF-NODA-MP-C6-CTHRSSVVC as a potential PET tracer for imaging of the CD163 receptor, which is expressed on M2-type tumor-associated macrophages. The conjugated peptide NODA-MP-C6-CTHRSSVVC was labeled with aluminum [18F]fluoride. Tracer binding and its biodistribution were evaluated in an in vitro binding assay and in healthy BALB/c mice, respectively. In addition, different treatments with cyclophosphamide in tumor-bearing mice were used to assess whether the tracer could detect differences in CD163 expression caused by differential TAM infiltration. After 7 days of treatment, animals were injected with [18F]AlF-NODA-MP-C6-CTHRSSVVC, and a 60-min dynamic PET scan was performed, followed by an ex vivo biodistribution study. [18F]AlF-NODA-MP-C6-CTHRSSVVC was prepared in 23 ± 6 % radiochemical yield and showed approximately 50 % of specific receptor-mediated binding in an in vitro binding assay on human CD163-expressing tissue homogenates. No CD163-mediated binding of [18F]AlF-NODA-MP-C6-CTHRSSVVC was detected by PET under normal physiological conditions in healthy BALB/c mice. On the other hand, CD163-positive xenograft tumors were clearly visualized with PET and a positive correlation was found between CD163 levels and the [18F]AlF-NODA-MP-C6-CTHRSSVVC tumor-to-muscle ratio (TMR) obtained from the PET images (Pearson r = 0.76, p = 0.002). No significant differences in the CD163 protein level and in the tracer uptake between treatment groups were found in the tumors. Taken together, [18F]AlF-NODA-MP-C6-CTHRSSVVC appears a promising candidate PET tracer for M2-type TAM, as it binds specifically to CD163 in vitro and its tumor uptake correlates well with CD163 expression in vivo.

A review on solid-state recycling of aluminum machining chips and their morphology effect on recycled part quality.

The increasing demand for sustainable manufacturing has revived the interest in solid-state recycling (SSR) as a promising alternative method for aluminum waste. In this context, chips generated during machining processes constitute a substantial portion of aluminum waste, offering significant potential for recycling and mitigating waste. However, the machining chip morphology significantly impacts the properties of chip-based recycled parts. This review paper examines the current state-of-the-art solid-state recycling methods, focusing on hot forging, extrusion, equal channel angular pressing, friction stir extrusion and field-assisted sintering. It investigates the impact of aluminum chip morphology on the properties of the directly recycled material, emphasizing the chip machining consequence on the final quality of the product. Several studies reported that the strain and operating temperature are the most influential factors in SSR processes, followed by chip size with an average length of less than 4 mm. Yet, the heating time up to 3 h also had a major impact on chip weld strength. The findings highlighted the significance of aluminum chip morphology in improving the quality of recycled material. The properties of direct recycled samples primarily depend on chip weld strength and microstructure. Overall, this study presented a comprehensive overview of the current state of solid-state recycling and emphasized the significance of chip morphology in advancing the recycling process. Consequently, it equips researchers with a valuable resource for developing effective strategies for sustainable recycling of aluminum chips with high quality.

Influence of heating temperature and time on mechanical-degradation, microstructures and corrosion performances of Teflon/granite coated aluminum alloys used for non-stick cookware.

This study explores the functional characteristics (erosion, corrosion, mechanical damage, and microstructural features) of non-stick cookware made from aluminum alloys. Typically coated with polytetrafluoroethylene (PTFE-Teflon) or ceramic for non-stick properties, we conducted a systematic investigation using corrosion, abrasion, and mechanical tests on six types of cookware from different manufacturers (Manuf-1-6). The cookware was heated at various temperatures [Room temperature (RT), 100, 175, 250, & 350 °C] and times (45 & 120 min). Tests included Taber wear, Adhesive Pull-off, hot & RT corrosion, and surface roughness measurements. Characterization involved optical microscopy, scanning electron microscope (SEM) with electron backscattered diffraction (EBSD), and x-ray diffraction (XRD). Ceramic-coated cookware from Manuf-4 demonstrated superior mechanical strength, wear, and corrosion resistance due to refined microstructures. Manuf-1's PTFE-coated cookware also performed well. Optimal results were observed when heating below 250 °C for up to 45 min. Prolonged heating and temperatures beyond 250 °C adversely affected internal structures of all cookware. Thus, it is advisable to use Al-based non-stick cookware below 250 °C for a maximum of 45 min.

Insights into the Fragmentation of Aluminum Hydride and Its Effect on Combustion and Agglomeration of HTPB Propellant.

AlH3 has gained considerable attention as a fuel additive due to its ability to offer high specific impulse and superior combustion performance. However, few studies have focused on the fragmentation and agglomeration behavior of AlH3. This study investigated the effects of fragmentation of AlH3 and AlH3/PVDF particles on the thermal decomposition, ignition, agglomeration, and combustion of HTPB propellants. Thermal analysis indicated that AlH3 and AlH3/PVDF can accelerate the decomposition of ammonium perchlorate by abundant active sites for the adsorption of the decomposition intermediates. Single-particle combustion uncovered the mechanism behind the directional spray of molten Al from the AlH3 particle and the fragmentation of the AlH3/PVDF particle. The melting of porous Al induces particle shrinkage due to solid-liquid interfacial tension and the structural restoration of the oxide shell, which consequently results in the sealing of cracks in the oxide shell of AlH3. Additionally, the accumulation of internal tensile stress leads to the reopening of these cracks and the directional ejection of the molten Al. The flexible oxide shell contributes to a smaller minimum normalized diameter of the AlH3/PVDF particle, aiding in the generation of internal tensile stress, while the sublimation of AlF3 induced the fragmentation. Synchrotron-based X-ray imaging revealed the formation of aggregates promoted by molten Al, the splitting of AlH3 aggregates due to hydrogen explosion, and the enhanced fragmentation of AlH3/PVDF due to the synergistic effect of hydrogen explosion and the sublimation of AlF3. Compared to raw particles, the CCPs (condensed combustion products) of SP2 propellant display a 48% reduction in average size (D50 = 24.5 µm), whereas there is an over 89% decrease in particle size for the CCPs of SP3 propellant (D50 = 5.14 µm). This study contributes to understanding the fragmentation of AlH3 and AlH3/PVDF upon ignition and combustion, providing valuable insights for the development and optimization of propellants containing AlH3.

The Effect of Bone Marrow Mesenchymal Stem Cells on Nestin and Sox-2 Gene Expression and Spatial Learning (Percent Alternation Y-Maze Test) against AlCl3-Induced Alzheimer's-like Pathology in a Rat Model.

Background: Alzheimer's disease (AD) is a neurodegenerative condition characterized by gradual cognitive impairment, including loss of synapses and nerve cells involved in learning, memory, and habit formation processes. Bone Marrow Mesenchymal Stem Cells (BM-MSCs) are multipotent cells. Because of their self-renewable, differentiation, and immunomodulatory capabilities, they are commonly used to treat many disorders. Hence, the current study intends to examine the effect of BM-MSCs transplantation on Aluminum chloride (AlCl3)-induced cognitive problems, an experimental model resembling AD's hallmarks in rats. Methods: The study was conducted in 2022 at The Biomedical Laboratory Faculty of Medicine, Andalas University, Indonesia. Adult male Wistar rats (three groups: negative control; no intervention+treatment with PBS; positive control: AlCl3+treatment with aqua dest; AlCl3+BM-MSCs: AlCl3+treatment with BM-MSCs, n=5 each) were treated daily with AlCl3 orally for five days. Stem cells were intraperitoneally injected into rats at a dose of 1x106 cells/rat. The same quantity of phosphate-buffered saline was given to the control group. One month after stem cell injection, the rat brain tissue was removed and placed in the film bottles that had been created. The expression of neural progenitor cell markers, including nestin and sex-determining Y-box 2 (SOX-2), was analyzed using real-time polymerase chain reaction (RT-PCR). Rats' cognitive and functional memory were examined using Y-maze. Data were analyzed using SPSS software (version 26.0) with a one-way analysis of variance (ANOVA) test. Results: The gene expression of nestin (29.74±0.42), SOX-2 (31.44±0.67), and percent alternation of Y-maze (67.04±2.28) increased in the AlCl3+BM-MSCs group compared to that in the positive control group. RT-PCR analysis indicated that nestin (P<0.001) and SOX-2 (P<0.001) were significantly enhanced in the AlCl3+BM-MSCs group compared to the positive control group. This group also indicated an increased percent alternation of Y-maze (P<0.001) in the AlCl3+BM-MSCs group compared to the positive control group. Conclusion: Due to its potential effects on cell therapy, BM-MSCs were found effective in a rat model of AD on the impairment of the rats' behavior and increased expression of neural progenitor cell markers.

Metal fluorides-multi-functional tools for the study of phosphoryl transfer enzymes, a practical guide.

Enzymes facilitating the transfer of phosphate groups constitute the most extensive protein families across all kingdoms of life. They make up approximately 10% of the proteins found in the human genome. Understanding the mechanisms by which enzymes catalyze these reactions is essential in characterizing the processes they regulate. Metal fluorides can be used as multifunctional tools to study these enzymes. These ionic species bear the same charge as phosphate and the transferring phosphoryl group and, in addition, allow the enzyme to be trapped in catalytically important states with spectroscopically sensitive atoms interacting directly with active site residues. The ionic nature of these phosphate surrogates also allows their removal and replacement with other analogs. Here, we describe the best practices to obtain these complexes, their use in NMR, X-ray crystallography, cryo-EM, and SAXS and describe a new metal fluoride, scandium tetrafluoride, which has significant anomalous signal using soft X-rays.

Regulating the Double-Way Traffic of Cations and Anions in Ambipolar Polymer Cathodes for High-Performing Aluminum Dual-Ion Batteries.

The strong Coulombic interactions between Al3+ and traditional inorganic crystalline cathodes present a significant obstacle in developing high-performance rechargeable aluminum batteries (RABs) that hold promise for safe and sustainable stationary energy storage. While accommodating chloroaluminate ions (AlCl4 -, AlCl2+, etc.) in redox-active organic compounds offers a promising solution for RABs, the issues of dissolution and low ionic/electronic conductivities plague the development of organic cathodes. Herein, electron donors are synthetically connected with acceptors to create crosslinked, bipolar-conjugated polymer cathodes. These cathodes exhibit overlapped redox potential ranges for both donors and acceptors in highly concentrated AlCl3-based ionic liquid electrolytes. This approach strategically enables on-site doping of the polymer backbones during redox reactions involving both donor and acceptor units, thereby enhancing the electron/ion transfer kinetics within the resultant polymer cathodes. Based on the optimal donor/acceptor combination, the bipolar polymer cathodes can deliver a high specific capacity of 205 mAh g-1 by leveraging the co-storage of AlCl4 - and AlCl2+. The electrodes exhibit excellent rate performance, a stable cycle life of 60 000 cycles, and function efficiently at high mass loadings, i.e., 100 mg cm-2, and at low temperatures, i.e., -30 °C. The findings exemplify the exploration of high-performing conjugated polymer cathodes for RABs through rational structural design.

A Concept of Local Coordination Number for the Characterization of Solute Clusters within Atom Probe Tomography Data.

Identifying clusters of solute atoms in a matrix of solvent atoms helps to understand precipitation phenomena in alloys, for example, during the age hardening of certain aluminum alloys. Atom probe tomography datasets can deliver such information, provided that appropriate cluster identification routines are available. We investigate algorithms based on the local composition of the neighborhood of solute atoms and compare them with traditional approaches based on the local solute number density, such as the maximum separation distance method. For an ideal solid solution, the pair correlation functions of the kth nearest solute atom in the coordination number representation are derived, and the percolation threshold and the size distribution of clusters are studied. A criterion for selecting optimal control parameters based on maximizing the phase separation by the degree of clustering is proposed for a two-phase system. A map of phase compositions accessible for cluster analysis is constructed. The coordination number approach reduces the influence of density variations commonly observed in atom probe tomography data. Finally, a practical cluster analysis technique applied to the early stages of aluminum alloy aging is described.

Alterations in internal threads of implant analog of different materials after multiple reuse.

The impact of multiple reuse on the alterations in internal threads of four different implant analogous composed of different materials (stainless steel (SS), aluminum (Al), titanium (Ti), and zirconia (Zr) by utilizing two die materials at different time durations is of interest to dentists. The spacing between the threads was measured using the impressions created for the interior threads of implant analogs, or replicas by stereomicroscope set to x50 at 0th, 3rd, 6th, 9th, and 12th interval. It was observed that there was decrease in distance between threads 1-2 as the increasing reuse at increasing time intervals in all implants analogs. However the decrease in distance between threads was low in Titanium implants analogs followed by Zircona implant analogs and the decrease was maximum in aluminum implants analogs followed by SS implant analogs. When there was evaluation of distance between threads 3-4 then it was observed that there was reduced decrease in distance between threads 3-4 as compared to threads 1-2 n all implant analogs. Similarly the reduction in distance between threads 5-6 was lesser as compared to threads 1-2 and threads 3-4. There was decrease in distance between threads 1-2 as the increasing reuse at increasing time intervals in all implants analogs. However, the reduction in distance between threads was lowest in Titanium implants analogs followed by Zircona implant analogs.

Thickness Effect of 2195 Al-Li Alloy Friction Stir Weld Fracture Toughness.

For damage tolerance design in engineering components, the fracture toughness value, KIC, of the material is essential. However, obtaining specimens of sufficient thickness from stir friction welded plates is challenging, and often, the experimental test values do not meet the necessary criteria, preventing the experimental fracture toughness, Kq, from being recognized as plane strain fracture toughness KIC. The fracture toughness Kq of 2195 Al-Li alloy welding seams with different thicknesses was measured on the forward and backward sides. Microstructure characterization was conducted by scanning electron microscope (SEM). The results indicated minimal significant differences in grain size between the advancing and retreating sides of the weld nugget zone. In specimens of the same thickness, fracture toughness measurements along the normal direction of the joint cross-section showed a high similarity between the advancing and retreating sides of the weld nugget zone. Utilizing the quantitative relationships between fracture toughness and sample thickness derived from both the fracture K and G criteria, it is possible to predict the fracture toughness of thick plates using thin plates. This study employs these relationships to calculate the fracture toughness KIC of 2195 aluminum-lithium alloy friction stir welds. The KIC values obtained are 41.65 MPa·m1/2 from the fracture K criterion and 43.54 MPa·m1/2 from the fracture G criterion.

Assessing the Performance of a Dual-Speed Tool When Friction Stir Welding Cast Mg AZ91 with Wrought Al 6082.

A novel dual-speed tool for which the shoulder and pin rotation speeds are separately established was utilized to friction stir weld cast magnesium AZ91 with wrought aluminum 6082-T6. To assess the performance and efficacy of the dual-speed tool, baseline dissimilar welds were also fabricated using a conventional FSW tool. Optical microscopy characterized the weld microstructures, and a numerical simulation enhanced the understanding of the temperature and material flow behaviors. For both tool types, regions of the welds contained significant amounts of the AZ91 primary eutectic phase, Al12Mg17, indicating that weld zone temperatures exceeded the solidus temperature of α-Mg (470 °C). Liquation, therefore, occurred during processing with subsequent eutectic formation upon cooling below the primary eutectic temperature (437 °C). The brittle character of the eutectic phase promoted cracking in the fusion zone, and the "process window" for quality welds was narrow. For the conventional tool, offsetting to the aluminum side (advancing side) mitigated eutectic formation and improved weld quality. For the dual-speed tool, experimental trials demonstrated that separate rotation speeds for the shoulder and pin could mitigate eutectic formation and produce quality welds without an offset at relatively higher weld speeds than the conventional tool. Exploration of various weld parameters coupled with the simulation identified the bounds of a process window based on the percentage of weld cross-section exceeding the eutectic temperature and on the material flow rate at the tool trailing edge. For the dual-speed tool, a minimum flow rate of 26.0 cm3/s and a maximum percentage of the weld cross-section above the eutectic temperature of 35% produced a defect-free weld.

Crystal Plasticity Finite Element Simulation of Grain Evolution Behavior in Aluminum Alloy Rolling.

In this study, the crystal plasticity finite element method was established by coupling the crystal plasticity and finite element method (FEM). The effect of rolling deformation and slip system of polycrystalline Al-Mg-Si aluminum alloy was investigated. The results showed that there was a pronounced heterogeneity in the stress and strain distribution of the material during cold rolling. The maximum strain and shear strain occurred at surface of the material. The smaller the grain size, the lower the strain concentration at the grain boundary. Meanwhile, a smaller strain difference existed between the grain interior and near the boundary. The rotation of grains leads to significant differences in deformation and rotation depending on their initial orientations during the rolling process. The slip system of (11-1)<-110> had a large effect on the plastic deformation, (111)<10-1> is second, and the effect of (1-11)<011> slip system on the plastic deformation is the smallest. After deformation, the grain orientation concentration was increased with deformation. Therefore, both the strength and volume fraction of texture were increased with the increase in rolling deformation. The experimental results of EBSD indicated that the large rolling reduction resulted in severe grain twisting, so the texture strength was increased. The simulation results were in close agreement with the experimental results. This study provides a theoretical basis for the rolling process, microstructure, and performance control of aluminum alloys.

Grain Structure and Texture Evolution in the Bottom Zone of Dissimilar Friction-Stir-Welded AA2024-T351 and AA7075-T651 Joints.

High-strength dissimilar aluminum alloys are difficult to connect by fusion welding, while they can be successfully joined by friction stir welding (FSW). However, the asymmetrical deformation and heat input that occur during FSW result in the formation of a heterogeneous microstructure in their welded zone. In this work, the grain structure and texture evolution in the bottom zones of dissimilar FSW AA2024-T351 and AA7075-T651 joints at different welding speeds (feeding speeds) were quantitatively investigated. The results indicated that dynamic recrystallization occurs in the bottom zones of dissimilar FSW joints, and equiaxed grains with low grain sizes are formed at the welding speed of 60-240 mm/min. A high fraction of the recrystallized grains were generated in the bottom zones of the joints at a low welding speed, while a high fraction of the substructured grains are produced at a high welding speed. Different types of shear textures are produced in the bottom zones of the joints; the number fraction of shear texture types depends on different welding speeds. This study helps to understand the mechanism of microstructure homogenization in dissimilar FSW joints and provides a basis for further improving the microstructure of the welded zone for engineering applications.

Insight into Role of Arc Torch Angle on Wire Arc Additive Manufacturing Characteristics of ZL205A Aluminum Alloy.

The arc torch angle greatly affected the deposition characteristics in the wire arc additive manufacturing (WAAM) process, and the relation between the droplet transition behavior and macrostructure morphology was unclear. This work researched the effect of torch angle on the formation accuracy, droplet transition behavior and the mechanical properties in the WAAM process on a ZL205A aluminum alloy. The results suggested that at the obtuse torch angle, part of the energy input was used to heat the existing molten pool, which was optimized for the longer solidification period of the molten pool. Therefore, the greater layer penetration depth at 100° resulted in the improved layer-by-layer combination ability. The obtuse torch angle was associated with the better formation accuracy on the sidewall surface due to the smaller impact on the molten pool, which was influenced by both the arc pressure and droplet impact force. The eliminated pores were optimized for the mechanical properties of depositions at a torch angle of 100°; thus, the tensile strength and elongation attained maximum values of 258.6 MPa and 17.1%, respectively. These aspects made WAAM an attractive mode for manufacturing large structural components on ZL205A aluminum alloy.