Explore the vast range of titles available.

PurposeMilitary and unmanned aerial vehicles (UAV) applications like rocket motor casings, missile covers and ship hulls use components that are made of maraging steel. Maraging steel has properties that are superior to other metals, making it more suitable for the fabrication of such components. A grey relational analysis (GRA) that is based on the Taguchi method has been utilised in the current study to optimise a laser beam welding (LBW) process. Further aspects such as GRA's optimum ranges and percentage contributions were also estimated.Design/methodology/approachA Taguchi L16 orthogonal array is utilised to design and conduct the experiments. Laser power (LP), welding speed (WS) and focal position (FP) are the three parameters are chosen for the process of welding. The output responses are the upper width of the heat-affected zone (HAZup), the upper width of the fusion zone (FZup) and the depth of penetration (DOP). The effect of the above key parameters on the responses was examined using an analysis of variance (ANOVA).FindingsThe results of ANOVA reveal that the parameter that has the most influence on the overall grey relational grade (GRG) is the FP. Finally, metallographic characterisation and a microstructural analysis are conducted on the weld bead geometry to demarcate the zone of HAZ and fusion zone (FZ).Originality/valueAs the most important criteria for LBW of maraging steels is the provision of higher DOP, higher FZ width and lower heat-affected zone, the study intended to prove the applicability of GRA technique in solving multi-objective optimisation problems in applications like defence and unmanned systems.

This study investigates the comminution behavior and beneficiation potential of lithium-bearing ores, zinnwaldite from Cínovec (Czech-Germany border) and lepidolite from Villasrubias (Spain) by integrating mineralogical analysis and mechanical characterization. The research is driven by Europe’s need for secure lithium supply chains. In particular, it focuses on the challenges associated with low-grade, fine-grained lithium micas found in hard-rock ores, which offer significant potential to supply in Europe but also pose substantial processing challenges. QMA (Quantitative Microstructural Analysis) revealed distinct differences in the textural and structural characteristics of the studied ores. Zinnwaldite-bearing rocks are coarser-grained with high interlocking and roughness, while lepidolite-bearing samples showed finer grains, lower roughness, and more disseminated mica distribution, indicated by their low clustering degree. In terms of mechanical characterization, zinnwaldite-rich ores have the lowest compressive strength, while lepidolite-rich samples showed the highest values, attributed to their finer grain size and more cohesive structure. This suggests that lepidolite may require higher energy input and finer crushing stages to achieve the target liberation size. These features influenced the breakage behavior observed during mechanical testing and comminution and are essential for enabling selective comminution, separating mica from gangue material. This study contributes to analyzing the potential of European hard-rock lithium resources from the perspective of upstream comminution, which is an essential step influencing downstream energy consumption, reagent use, and overall recovery efficiency. The results of this research emphasize that selective comminution should not rely solely on mineral hardness contrasts but must incorporate microstructural parameters such as clustering, grain size distribution, and orientation.

As the boundary between the Indochina and the South China blocks, the Ailao Shan-Red River (ASRR) shear zone underwent a sinistral strike-slip shearing which is characterized by ductile deformation structures along the Ailao Shan range. The timing issue of left-lateral shearing along the ASRR shear zone is of first-order importance in constraining the nature and regional significance of the shear zone. It has been, therefore, focused on by many previous studies, but debates still exist on the age of initiation and termination of shearing along the shear zone. In this paper, we dated 5 samples of granitic plutons (dykes) along the Ailao Shan shear zone. Zircon U–Pb ages of four sheared or partly sheared granitic rocks give ages of 30.9 ± 0.7, 36.6 ± 0.1, 25.9 ± 1.0 and 27.2 ± 0.2 Ma, respectively. An undeformed granitic dyke intruding mylonitic foliation gives crystallization age of 21.8 ± 1 Ma. The Th/U ratios of zircon grains from these rocks fall into two populations (0.17–1.01 and 0.07–0.08), reflecting magmatic and metamorphic origins of the zircons. Detailed structural and microstructural analysis reveals that the granitic intrusions are ascribed to pre-, syn- and post-shearing magmatisms. The zircon U–Pb ages of these granites provide constraints on timing of the initiation (later than 31 Ma from pre-shearing granitic plutons, but earlier than 27 Ma from syn-shearing granitic dykes) and termination (ca. 21 Ma from the post-shearing granitic dykes) of strong ductile left-lateral shearing, which is consistent with previous results on the Diancang Shan and Day Nui Con Voi massifs in the literature. We also conclude that the left-lateral shearing along the ASRR shear zone is the result of southeastward extrusion of the Indochina block during the Indian–Eurasian plate collision. Furthermore, the left-lateral shearing was accompanied by the ridge jump, postdating the opening, of the South China Sea.

The current research explores additive manufacturing of a multi-phase material using dual-wire plasma-directed energy deposition technology. With this approach, new materials can be designed and tested easily on the basis of commercially available consumables. In this work, AlSi5 and CuAl8 solid wire consumables are used to produce a specific AlCuSi alloy by controlling the welding parameters and the wire feed ratio. Initial experimentation results in an alloy with 85.7 at.% aluminum, 8.4 at.% copper, 2.7 at.% silicon, and 3.2 at.% magnesium, but with some instabilities during the process. The presence of magnesium in the chemical composition could be related to plasma interaction with the substrate during the welding process. After optimizing the process parameters, the chemical composition obtained is about 76.3 at.% aluminum, 19.9 at.% copper, and 3.8 at.% silicon. Using microstructural analysis via light and scanning electron microscopy, defects such as pores and inadequately melted Cu wire material are observed in all materials produced. Although the optimization of the melting process improved the microstructure, it also increased the copper content, which in turn exerts a significant influence on the mechanical properties. Mechanical testing indicates significant embrittlement. The results underscore that the microstructure is heavily influenced by the chemical composition. Microstructural changes caused by the higher copper content, i.e., in particular the increase of the volume fraction of brittle intermetallic phases such as θ-Al 2 Cu, result in severe embrittlement of the obtained materials, denoted by higher hardness and reduced toughness. We conclude that the use of dual-wire plasma additive manufacturing can develop new materials by in situ alloying.

Thermal, microstructural and mechanical analyzes were carried out in the present work with the Al–3Cu–0.5Nb (wt%) alloy. Experimental cooling curves for non-equilibrium and close-to-equilibrium cooling conditions were obtained to thermally characterize the liquidus temperature (TL) of the investigated alloy and thus applied set superheat in the liquid metal. In turn, unsteady-state horizontal solidification experiment was elaborated using a water-cooled solidification device. A temperature mapping was performed during solidification and the thermal data obtained were used to determine the solidification thermal parameters, such as growth and cooling rates (VL and TR, respectively). The as-cast ingot was characterized for microstructural analysis by optical (OM) and scanning electronic microscope (SEM/EDS). The typical solidification microstructure consisted of a dendritic network as an Al-rich primary phase (Alα) plus Fe and Al2Cu intermetallic phases within the interdendritic regions. For the assumed solidification conditions, Nb was observed in the investigated Al–Cu–Nb alloy completely dissolved in the Al-rich matrix, not forming the peritectic reaction in the phase equilibrium diagram of the Al–Nb system. The primary phase was quantified by measuring the secondary dendritic spacings (λ2), and a mathematical association between VL-λ2 and TR-λ2 was proposed. Vickers microhardness (HV) tests were carried out, and there was no variation in HV along the horizontal length of the as-cast ingot. On the other hand, higher HV values were reached when measured in the interdendritic phases. A comparison with the literature was also conducted in this paper.

Abaca fiber degradation in concrete owing to its alkaline nature decreases the strength of concrete. This research focuses on overcoming the degradation by alkaline treatment with sodium hydroxide (NaOH) to improve fiber performance. This study was completed with the extraction process of fiber, mechanical properties, micro-structural analysis of composite fiber concrete for both M30 and M40 grades, and durability performance if the fiber content, aspect ratio of fiber and molarities of Sodium Hydroxide were optimized using splitting tensile strength of the concrete matrix and it was found that the optimum percentage of fiber content was 1% at 12% alkali treatment. The composite concrete has achieved an increase of 2700 to 3100 kg m −2 in split tensile strength with treated abaca fibers compared to untreated fiber concrete. In addition, treated abaca fiber concrete provides better performance in mechanical and durability studies. The binding nature of fiber concrete is better than that of conventional concrete, which is evidenced in microstructural analysis. This study ultimately concluded that the treated abaca fiber composite concrete is a better alternative to commercially available untreated abaca fibers and other natural fibers.

Microstructural characterization and analysis is the foundation of microstructural science, connecting materials structure to composition, process history, and properties. Microstructural quantification traditionally involves a human deciding what to measure and then devising a method for doing so. However, recent advances in computer vision (CV) and machine learning (ML) offer new approaches for extracting information from microstructural images. This overview surveys CV methods for numerically encoding the visual information contained in a microstructural image using either feature-based representations or convolutional neural network (CNN) layers, which then provides input to supervised or unsupervised ML algorithms that find associations and trends in the high-dimensional image representation. CV/ML systems for microstructural characterization and analysis span the taxonomy of image analysis tasks, including image classification, semantic segmentation, object detection, and instance segmentation. These tools enable new approaches to microstructural analysis, including the development of new, rich visual metrics and the discovery of processing-microstructure-property relationships.

The cracking of screws made from medium-carbon cold heading steel for the electronic parking brake system was studied through the analysis of the microstructure and the systematic investigation of the whole process, and the corresponding improvement measures were proposed at last. Results showed that the cracks initiated at the root of the threads due to insufficient plasticity generated by the large pressure during thread rolling were the resource of the fracture, which was further extruded during the turning process, while the centering condition was not well. It was necessary to adjust the appropriate parameters of rolling pressure and rolling time to avoid heavy work hardening and also pay attention to the cleanness on the surface of the rolling plate or the wheel.

The aim of this study is to characterise the changes in mechanical properties and to provide a comprehensive micro-structural analysis of Harcourt granite over different pre-heating temperatures under two cooling treatments (1) rapid and (2) slow cooling. A series of uniaxial compression tests was conducted to evaluate the mechanical properties of granite specimens subjected to pre-heating to temperatures ranging from 25–1000 °C under both cooling conditions. An acoustic emission (AE) system was incorporated to identify the fracture propagation stress thresholds. Furthermore, the effect of loading and unloading behaviour on the elastic properties of Harcourt granite was evaluated at two locations prior to failure: (1) crack initiation and (2) crack damage. Scanning electron microscopy (SEM) analyses were conducted on heat-treated thin rock slices to observe the crack/fracture patterns and to quantify the extent of micro-cracking during intense heating followed by cooling. The results revealed that the thermal field induced in the Harcourt granite pore structure during heating up to 100 °C followed by cooling causes cracks to close, resulting in increased mechanical characteristics, in particular, material stiffness and strength. Thereafter, a decline in mechanical properties occurs with the increase of pre-heating temperatures from 100 °C to 800 °C. However, the thermal deterioration under rapid cooling is much higher than that under slow cooling, because rapid cooling appears to produce a significant amount of micro-cracking due to the irreversible thermal shock induced. Multiple stages of loading and unloading prior to failure degrade the elastic properties of Harcourt granite due to the damage accumulated through the coalescence of micro-cracks induced during compression loading. However, this degradation is insignificant for pre-heating temperatures over 400 °C, since the specimens are already damaged due to excessive thermal deterioration. Moreover, unloading after crack initiation tends to cause insignificant irreversible strains, whereas significant permanent strains occur during unloading after crack damage, and this appears to increase with the increase of pre-heating temperature over 400 °C.

π-Conjugated organic semiconductors have been explored in several optoelectronic devices, yet their use in molecular detection as surface-enhanced Raman spectroscopy (SERS)-active platforms is unknown. Herein, we demonstrate that SERS-active, superhydrophobic and ivy-like nanostructured films of a molecular semiconductor, α,ω-diperfluorohexylquaterthiophene (DFH-4T), can be easily fabricated by vapour deposition. DFH-4T films without any additional plasmonic layer exhibit unprecedented Raman signal enhancements up to 3.4 × 10 3 for the probe molecule methylene blue. The combination of quantum mechanical computations, comparative experiments with a fluorocarbon-free α,ω-dihexylquaterthiophene (DH-4T), and thin-film microstructural analysis demonstrates the fundamental roles of the π-conjugated core fluorocarbon substitution and the unique DFH-4T film morphology governing the SERS response. Furthermore, Raman signal enhancements up to ∼10 10 and sub-zeptomole (<10 −21 mole) analyte detection were accomplished by coating the DFH-4T films with a thin gold layer. Our results offer important guidance for the molecular design of SERS-active organic semiconductors and easily fabricable SERS platforms for ultrasensitive trace analysis. Highly nanostructured purely organic films are shown to enhance the Raman signal of methylene blue molecules by three orders of magnitude, due to the unique molecular geometry, morphology and electronic properties of the films.