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The aim of this investigation was to evaluate the effect of etching protocols on bond strength, surface roughness, and mechanical properties of a zirconia-reinforced lithium silicate (ZLS) CAD/CAM-ceramic. In total, 100 bars (ISO 6872), 75 plaques, and 25 cubes were cut from ZLS blocks(Vita Suprinity®). The surfaces were standardized, crystallized and divided into five groups: 1. control (no/treatment-C), 2. 5%-Hydrofluoric-acid (HF)/20 s (HF5%20s), 3.HF5%60s, 4.HF10%20s, and 5.HF10%60s. Flexural strength (FS) (three-point bending test, 1 mm/min), roughness (Pa), and micro-shear bond-strength (µSBS) tests were performed. The data were statistically analyzed with one-way ANOVA, Tukey's test (p ˂ 0.05) and Weibull (FS data). C showed higher Pa (1.176 ± 0.370 µm) than HF10%60s (0.627 ± 0.236 µm) and all other groups. Groups C and 20 s showed the most irregular surface patterns. The FS results were not influenced by etching protocols, while the Weibull modulus was, with the 5%HF groups being the most reliable (m: 5.63/6.70), while C and HF10%60s (m: 2.78/2.73) were the least reliable. All fractures originated from surface defects on the treated side of specimens. The 5%HF groups showed higher µSBS (20 s: 21.35 ± 4.70 MPa; 60 s: 23.50 ± 4.27 MPa) than the 10%HF groups (20 s: 14.51 ± 2.47 MPa; 60 s: 16.54 ± 3.12 MPa) and C (6.46 ± 2.71 MPa). The most prevalent failure pattern was "mixed" for etched groups, and "adhesive" for C. Etching protocols affect the evaluated properties by roughening materials' surface and, in some cases, regularizing surface defects. The best overall outcomes were achieved when applying 5%HF. [ABSTRACT FROM AUTHOR]

In this study, we utilized Selective Laser Melting (SLM) technology to fabricate a magnesium alloy, and subsequently subject it to micro-arc oxidation treatment. We analyzed and compared the microstructure, elemental distribution, wetting angle, and corrosion resistance of the SLM magnesium alloy both before and after the micro-arc oxidation process. The findings indicate that the SLM magnesium alloy exhibits surface porosity defects ranging from 2% to 3.2%, which significantly influence the morphology and functionality of the resulting film layer formed during the micro-arc oxidation process. These defects manifest as pores on the surface, leading to an uneven distribution of micropores with varying sizes across the layer. The surface roughness of the 3D-printed magnesium alloy exhibits a high roughness value of 180 nanometers. The phosphorus (P) content is lower within the film layer compared to the surface, suggesting that the Mg3(PO4)2 phase predominantly resides on the surface, whereas the interior is primarily composed of MgO. The micro-arc oxidation process enhances the hydrophilicity and corrosion resistance of the SLM magnesium alloy, thereby potentially endowing it with bioactivity. Additionally, the increased surface roughness post-treatment promotes cell proliferation. However, certain inherent defects present in the SLM magnesium alloy samples negatively impact the improvement of their corrosion resistance. [ABSTRACT FROM AUTHOR]

Laser metal deposition is a promising way to repair the surface defects of single-crystal components in turbo engines. Understanding the mechanisms and improving the efficiency of the repair have been long-standing problems. In this study, the influence of the substrate orientation on the laser metal deposition (LMD) was investigated and its effect on repair layer-step was examined. LMD experiments were conducted on single crystal superalloys with a normal substrate orientation (001)/[100] and with an optimized substrate orientation (101)/[10 1 ¯ ]. It reveals that the laser cladding with the optimized orientation leads to a larger height of the [001] dendrite region than that with the normal orientation. The calculated results of the growth velocity, thermal gradient, and susceptibility to CET in the dendrite-preferred growth direction indicate that, for the (101)/[10 1 ¯ ] orientation, the [001]/[100] boundary is located at relative high position in each layer, which not only decreases the formation ability of stray grain significantly, but also eliminates the appearance of the maximum susceptibility. This makes the necessary dilution position much higher, and thus, a large cladding step can be selected. Our findings could find potential applications in laser repair of single-crystal components. [ABSTRACT FROM AUTHOR]

The fatigue performance of laser powder bed fusion-fabricated Ti-6Al-4V alloy was investigated using four-point bending testing. Specifically, the effects of keyhole and lack-of-fusion porosities along with various surface roughness parameters, were evaluated in the context of pore circularity and size using 2D optical metallography. Surface roughness of Sa = 15 to 7 microns was examined by SEM, and the corresponding fatigue performance was found to vary by 102 cycles to failure. The S–N curves for the various defects were also correlated with process window examination in laser beam power–velocity (P–V) space. Basquin's stress-life relation was well fitted to the experimental S–N curves for various process parameters except keyhole porosity, indicating reduced importance for LPBF-fabricated Ti-6Al-4V alloy components. [ABSTRACT FROM AUTHOR]

This study investigates the effects of a back plate preheating assistance system and deep rolling (DR) on axial force and tunnel defects during friction stir welding (FSW). Different preheating configurations—advancing side (AS), retreating side (RS), and both sides—were examined to evaluate their impact on axial force reduction, temperature distribution, and defect minimization. Axial force measurements were taken using a dynamometer, and temperature histories were recorded with a thermal camera. The results demonstrate that a preheating temperature of 200 °C is optimal, reducing axial force by 30.24% and enhancing material flow. This temperature also facilitated deeper tool penetration, especially when preheating was applied to both sides. Preheating on the AS resulted in the smallest tunnel defects, reducing defect size by 80.15% on the RS and 96.91% on the AS compared to the non-preheated condition. While DR further reduced tunnel defects, its effectiveness was limited by the proximity of defects to the surface. These findings offer significant insights for improving the FSW process. [ABSTRACT FROM AUTHOR]

Titanium carbide (TiC) coatings were prepared on the surface of AlFeCoCrNiCu high-entropy alloy blocks using electro-spark deposition (ESD). The microhardness and corrosion resistance of the TiC coatings prepared under different voltage and capacitance process parameters were studied. The research shows that the maximum microhardness of the TiC coating on sample 4 (working voltage of 20 V, working capacitance of 1000 μF) is 844.98 HV, which is 81.5% higher than the microhardness of the substrate. This is because the deposition energy increases with the increase in voltage, and the adhesion and aggregation between the coating and the substrate are enhanced, increasing the hardness of the coating. It is worth noting that excessive deposition energy can increase surface defects and reduce the microhardness of the coating surface. Electrochemical testing analysis shows that the corrosion current density of the TiC coating is the lowest (9.475 × 10−7 ± 0.06 × 10−7), and the coating impedance is the highest (2.502 × 103 Ω·com2). The absolute phase angle value is the highest (about 72°). The above indicates that the TiC coating prepared with a working voltage of 20 V and a working capacitance of 1000 μF has better microhardness and corrosion resistance. [ABSTRACT FROM AUTHOR]

Tungsten and its alloys have a high atomic number, high melting temperature, and high thermal conductivity, which make them fairly appropriate for use in nuclear applications in an extremely harsh radioactive environment. In recent years, there has been growing research interest in using additive manufacturing techniques to produce tungsten components with complex structures. However, the critical bottleneck for tungsten engineering manufacturing is the high melting temperature and high ductile-to-brittle transition temperature. In this study, laser powder bed fusion has been studied to produce bulk pure tungsten. And finite element analysis was used to simulate the temperature and stress field during laser irradiation. The as-printed surface as well as transverse sections were observed by optical microscopy and scanning electron microscopy to quantitatively study processing defects. The simulated temperature field suggests small-sized powder is beneficial for homogenous melting and provides guidelines for the selection of laser energy density. The experimental results show that ultra-dense tungsten bulk has been successfully obtained within a volumetric energy density of 200–391 J/mm3. The obtained relative density can be as high as 99.98%. By quantitative analysis of the pores and surface cracks, the relationships of cracks and pores with laser volumetric energy density have been phenomenologically established. The results are beneficial for controlling defects and surface quality in future engineering applications of tungsten components by additive manufacturing. [ABSTRACT FROM AUTHOR]

To extend the working life of products made of titanium alloy, it is necessary to improve the polishing method to diminish the remaining defects on the workpiece surface. The Halbach array-assisted magnetic abrasive particle polishing method for titanium alloy was employed in this work. The distribution of magnetic field strength was simulated and verified at first to learn the characteristics of the Halbach array used in this work. Then, the polishing performance of the polishing tool was studied by conducting the polishing test, which aimed to display the relationship between shear force and surface roughness with polishing time, and the surface morphology during polishing was also analyzed. Following the establishment of the response surface model, a study on the optimal polishing parameters was conducted to obtain the suitable parameters for maximum shear force and minimum surface roughness. The results show that the maximum shear force 6.11 N and minimum surface roughness Sa 88 nm can be attained, respectively, under the conditions of (1) polishing tool speed of 724.254 r·min−1, working gap of 0.5 mm, and abrasive particle size of 200 μm; and (2) polishing tool speed of 897.87 r·min−1, working gap of 0.52 mm, and abrasive particle size of 160 μm. [ABSTRACT FROM AUTHOR]

High-volume fraction silicon carbide particle-reinforced aluminum (SiCp/Al) has a promising application for its high specific strength, wear resistance, and thermal conductivity. However, SiCp/Al components with a high-volume fraction are prone to poor surface quality and defects such as fractures, cracks, and micro-pits. It has been reported that ultrasonic-assisted grinding machining (UAG) helps to improve the quality of SiCp/Al machined surfaces. However, the differences between SiCp/Al with different volume fractions obtained by UAG machining are not clear. Therefore, a comparative study of surface roughness, morphology, and cutting force was carried out by UAG machining on SiCp/Al samples with volume fractions of 45% and 60%. Compared to the 45% volume fraction SiCp/Al, the 60% volume fraction SiCp/Al has a higher cutting force and roughness under the same machining parameters. In addition, experiments have shown that cutting forces and surface roughness can be reduced by increasing the tool speed or decreasing the feed rate. UAG machining with an ultrasonic amplitude within 4 μm can also reduce cutting forces and surface roughness. However, more than 6 μm ultrasonic amplitude may lead to an increase in roughness. This study contributes to reasonable parameter settings in ultrasonically-assisted grinding of SiCp/Al with different volume fractions. [ABSTRACT FROM AUTHOR]

Hydrogenation–Disproportionation–Desorption–Recombination (HDDR) Nd2Fe14B particles have excellent magnetic properties, but the magnetic properties of powder are not uniform across different particle sizes. The remanence and maximum magnetic energy products of samples with a particle size of 120 μm are 14.0 kGs and 41.35 MGOe, while the products of samples with a particle size of 60 μm are only 13.3 kGs and 36.31 MGOe. The macroscopic morphology of HDDR Nd2Fe14B particles and the gradient distribution of microstructures in different micro-regions were observed. By modifying the macroscopic morphology of the particles, the poorly oriented clusters on the surface of the particles were precisely eliminated, and the remanence and maximum magnetic energy products of the particles increased to 14.5 kGs and 45 MGOe, respectively. Compared with the original particles, the samples after mechanical grinding had better grain arrangement. The effects of the nanocrystalline c-axis and field misalignment angle θ on the magnetic properties of HDDR Nd2Fe14B particles were investigated through micromagnetic simulation. The targeted removal of macroscopic defects on the particle surface contributed to a 3.6% increase in remanence and an 8.8% increase in the maximum magnetic energy product, offering a promising approach to enhance the microstructure of high-performance HDDR Nd2Fe14B particles. [ABSTRACT FROM AUTHOR]

The discoloration switching appearing in the initial and final growth stages of 4H-silicon carbide (4H-SiC) single crystals grown using the physical vapor transport (PVT) technique was investigated. This phenomenon was studied, investigating the correlation with linear-type micro-pipe defects on the surface of 4H-SiC single crystals. Based on the experimental results obtained using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and micro-Raman analysis, it was deduced that the orientation of the 4H-SiC c-axis causes an axial change that correlates with low levels of carbon. In addition, it was confirmed that the incorporation of additional elements and the concentrations of these doped impurity elements were the main causes of discoloration and changes in growth orientation. Overall, this work provides guidelines for evaluating the discoloration switching in 4H-SiC single crystals and contributes to a greater understanding of this phenomenon. [ABSTRACT FROM AUTHOR]

A new strategy for the high-throughput characterization of the mechanical homogeneity of metallurgical materials is proposed. Based on the principle of hydrostatic transmission and the synergistic analysis of the composition, microstructure, defects, and surface profile of the chosen material, the microstrain characteristics and changes in surface roughness after isostatic pressing were analyzed. After isostatic pressing, two types of microstrains were produced: low microstrain (surface smoothening with decreasing roughness) and large microstrain (surface roughening with increasing roughness). Furthermore, the roughness of the roughened microregions could be further classified based on the strain degree. The phenomenon of weak-interface damage with a large microstrain (plastic deformation, cleavage fracture, and tearing near nonmetallic inclusions) indicated that the surface microstrain analysis could be a new method of high-throughput characterization for microregions with relatively poor micromechanical properties. In general, the effect of isostatic pressing on the surface microstrain of heat-resistant steel provides a promising strategy for achieving high-throughput screening and statistically characterizing microregions with poor micromechanical properties, such as microregions containing microcracks, nonmetallic inclusions, pores, and other surface defects. [ABSTRACT FROM AUTHOR]

The emergence of defects during the early production phases of ferrous-alloy additively manufactured (AM) parts poses a serious threat to their versatility and adversely impacts their overall mechanical performance in industries ranging from aerospace engineering to medicine. Lack of fusion and gas entrapment during the manufacturing stages leads to increased surface roughness and porosities in the finished part. In this study, the efficacy of employing electroless nickel–boron (Ni-B) deposition to fill and level simulated AM defects was evaluated. The approach to levelling was inspired by the electrochemical deposition techniques used to fill vias in the electronics industry that (to some extent) resemble the size and shape of AM-type defects. This work investigated the use of surfactants to attenuate surface roughness in electroless nickel coatings, thereby achieving the preferential inhibition of the coating thickness on the surface and promoting the filling of the simulated defects. A cationic surfactant molecule, CTAB (cetyltrimethyl ammonium bromide), and a nonpolar surfactant, PEG (polyethylene glycol), at different concentrations were tested using a Ni-B electrolyte for the levelling study. It was found that the use of electroless Ni-B to fill simulated defects on ferrous alloys was strongly influenced by the concentration and nature of the surfactant. The highest levelling percentages were obtained for the heavy-molecular-weight PEG-mediated coatings at 1.2 g/L. The results suggest that electroless Ni-B deposition could be a novel and facile approach to filling defects in ferrous-based AM parts. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) emerges as an enticing material for visible-light-driven photocatalysis owing to its remarkable stability, low toxicity, and abundance. However, its inherent shortcomings, such as a short hole diffusion length and high recombination rate, hinder its practical application. Recently, oxygen vacancies (Vo) within hematite have been demonstrated to modulate its photocatalytic attributes. The effects of Vo can be broadly categorized into two opposing aspects: (1) acting as electron donors, enhancing carrier conductivity, and improving photocatalytic performance and (2) acting as surface carrier traps, accelerating excited carrier recombination, and deteriorating performance. Critically, the generation rate, distribution, role, and behavior of Vo significantly differ for synthesis methods due to differences in formation mechanisms and oxygen diffusion. This complexity hampers simplified discussions of Vo, necessitating careful investigation and nuanced discussion tailored to the specific method and conditions employed. Among various approaches, hydrothermal synthesis offers a simple and cost-effective route. Here, we demonstrate a hydrothermal synthesis method for Vo introduction to hematite using a carbon source, where variations in the heating rate have not been previously explored in terms of their influence on Vo generation. The analyses revealed that the concentration of Vo was maximized at a heating rate of 16 °C/min, indicative of a high density of surface defects. With regard to photocatalytic performance, elevated heating rates (16 °C/min) fostered the formation of Vo primarily on the hematite surface. The photocatalytic activity was 7.1 times greater than that of the sample prepared at a low heating rate (2 °C/min). These findings highlight the crucial role of surface defects, as opposed to bulk defects, in promoting hematite photocatalysis. Furthermore, the facile control over Vo concentration achievable via manipulating the heating rate underscores the promising potential of this approach for optimizing hematite photocatalysts. [ABSTRACT FROM AUTHOR]

Abrasive suspension jet (ASJ), an accurate cold-cutting technology, can address traditional processing issues relating to carbon-fiber-reinforced plastics (CFRPs) like tool wear, interlayer delamination, large heat-affected zone, and low surface roughness. This study employed the use of an ASJ to cut CFRPs and an ultra-depth optical microscope to scan the cut surface to analyze interlayer delamination, surface roughness, kerf taper, and shoulder damage. Regression analysis was conducted to establish a prediction model for cutting quality based on surface roughness, kerf taper, and shoulder damage. Various types of CFRP cutting quality were analyzed using jet parameters. It was found that the use of ASJ to process CFRP results in the following defects: The range of surface roughness variation is from 0.112 μm to 0.144 μm. Surface roughness is most influenced by stand-off distance, followed by traverse speed and jet pressure. The range of kerf taper variation is from 4.737° to 10.1°. Kerf taper is most influenced by stand-off distance, followed by jet pressure and traverse speed. The range of shoulder damage variation is from 3.384 μm2 to 10 μm2. Shoulder damage is most influenced by jet pressure, followed by traverse speed and stand-off distance. A prediction model for cutting quality was developed based on surface roughness, kerf taper, and shoulder damage, providing data support for ASJ cutting of CFRPs. The optimal parameter combination is a stand-off distance of 1 mm, a jet pressure of 30 MPa, and a traverse speed of 30 mm/min. [ABSTRACT FROM AUTHOR]

In this paper, the effects of carbon nanotube defects and a copper surface oxide layer on a carbon nanotube–copper interface were studied via first-principles. A defect-free CNT-Cu interface, Stone–Wales defect CNT-Cu interface, single-hole and double-hole defect CNT-Cu interface, and Cu2O-Cu interface were simulated and calculated. By simulating the differential charge density, atomic population, bond population and density of states of the interface model, the effects of various defects on the interface bonding and electrical conductivity of the composites during the preparation of the CNT-reinforced copper matrix composites were analyzed, which provided theoretical guidance for the preparation of CNT/Cu composites. After that, copper matrix composites with different CNT defect contents were prepared via different rolling deformation processes. Their hardness and electrical conductivity were tested, and the results were consistent with the results obtained via the first-principles calculations. [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxanes (POSS) and hybrid organo-halide perovskites are two important types of hybrid nanoscale frameworks with great potential in materials chemistry. Both are currently under intensive investigation for a wide range of possible applications. Recent results suggest that POSS can be attractive passivating and structure-controlling agents for perovskite materials. In this review, we present the importance of POSS in engineering the structures of inorganic cesium-halide perovskites CsPbX3 (X = Cl, Br, I) to create a new class of hybrid derivatives with improved properties. The combination of these two components can be an effective strategy for controlling the perovskite crystallization process. In addition, passivation of surface defects/bulk and the engineering of energy and optoelectronic properties of perovskite-based materials can be achieved following this method. In this minireview, we summarized the existing literature reports on the structural specificity and properties of hybrid POSS perovskites. [ABSTRACT FROM AUTHOR]

To investigate the micro-grinding process and performance of 2.5D Cf/SiC composites and 2.5D SiCf/SiC composites in depth, single-factor micro-grinding experiments were conducted by using SiC ceramics as a comparison. Differences in the material removal process, surface microstructure, surface roughness, and grinding force of the three materials under the same grinding parameters were comparatively analyzed. The results indicate that crack propagation is severe during the micro-grinding process of SiC ceramics. The ground surface is uneven, accompanied by pit defects and large surface roughness Ra. However, the presence of reinforcing fibers and interfaces in the two types of composites can inhibit crack propagation or change their extension directions. Therefore, their surfaces are smooth and flat after grinding, with small defects and low surface roughness Ra. In addition, the grinding processes of the two composites are both related to fiber orientation. There are differences in crack propagation paths and fiber fracture positions in the weft fiber layer and the radial fiber layer, which result in different forms of grinding defects. During micro-grinding, the real-time force signals of 2.5D Cf/SiC composites and 2.5D SiCf/SiC composites are relatively stable, while the signals of SiC ceramics have a large number of spikes. The average micro-grinding force of the three materials is: SiC ceramics > 2.5D SiCf/SiC composites > 2.5D Cf/SiC composites. [ABSTRACT FROM AUTHOR]

Transmission gear is a key component of vehicles and its surface integrity affects the safety of the transmission system as well as the entire mechanical system. The design and optimization of allowances in form grinding are important for improving dimensional accuracy and machining efficiency during the manufacturing of heavy-duty gears. This work aims to investigate the effects of grinding allowance allocation on surface morphology, grinding temperature, microstructure, surface roughness, and microhardness fluctuation during the form grinding of 20Cr2Ni4A gears. Results indicated that grinding temperature was primarily influenced by rough grinding involving significant grinding depths exceeding 0.02 mm. The ground surface exhibited slight work hardening, while thermal softening led to a reduction in microhardness of around 40 HV. Ground surface roughness Ra varied from 0.930 μm to 1.636 μm, with an allowance allocation of the last two passes exerting the most significant influence. Analysis of surface and subsurface microstructures indicated that a removal thickness of 0.02 mm during fine grinding was insufficient to eliminate the roughness obtained from rough grinding. Evident ridges, gullies, and surface defects such as material extraction, adhesion, and plastic deformation were also observed. The proposed grinding strategy was validated in practical manufacturing with good surface quality and geometrical accuracy. [ABSTRACT FROM AUTHOR]

The tool structure is an important factor affecting the damage of CFRP/Ti stacks machining. However, the impact of tool structure on the formation process of stacks hole damage cannot be fully revealed through experimental methods alone. In contrast, finite element simulation can effectively overcome the limitations of experiments. In this study, a numerical simulation model is established to investigate the relationship between step drill structure and formation process of CFRP/Ti stacks hole damage. Based on this, the research discusses the effect of step drill structure on the burr height of Ti layer, delamination of CFRP, aperture deviation, defects in hole surface. The results show that when the stacking sequence is CFRP to Ti, the burr height of Ti at hole exit decreases first and then increases with the rising of the ratio of primary drill bit diameter to secondary drill bit diameter (kd). When kd is 0.6, the burr height of Ti at hole exit is the lower. As kd increasing from 0.4 to 1.0, delamination factor of CFRP increases by 2.57%, which are affected little by the step drill structure due to the support of Ti. Besides, the aperture size deviation decreases first then increases with the rising of kd, and the minimum aperture size deviation is 2.09 μm when kd is 0.6. In addition, as kd is 0.6, the hole wall defect is fewer. In conclusion, step drill with kd of 0.6 is suitable for drilling of CFRP/Ti stacks. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM) is an excellent characterization method to analyze the size, morphology, crystalline state, and microstructure of perovskite quantum dots (PeQDs). Nevertheless, the electron beam of TEM as an illumination source provides high energy, which causes morphological variation (fusion and melting) and recession of the crystalline structure in low radiolysis tolerance specimens. Hence, a novel and facile strategy is proposed: electron beam peel [PbBr6]4− octahedron defects from the surface of QDs to optimize the crystal structure. TEM and high-angle annular dark-field scanning TEM (HAADF) tests indicate that the [PbBr6]4− octahedron would be peeled from the surface of QDs when QDs samples were irradiated under high-power irradiation, and then a clear image would be obtained. To avoid interference from a protective film of "carbon deposits" on the surface of the sample when using high resolution TEM, amorphous carbon film (15–20 nm) was deposited on the surface of QDs film and then characterized by TEM and HAADF. The detection consequences showed that the defection of PbBr2 on the surface of QDs will gradually disappear with the extension of radiation time, which further verifies the conjecture. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) allows for optimized part design, reducing weight compared to conventional manufacturing. However, the microstructure, surface state, distribution, and size of internal defects (e.g., porosities) are very closely related to the AM fabrication process and post-treatment operations. All these parameters can have a strong impact on the corrosion and fatigue performance of the final component. Thus, the fatigue-corrosion behavior of the 3D-printed (L-PBF) AlSi10Mg aluminum alloy has been investigated. The influence of load sequence (sequential vs. combined) was explored using Wöhler diagrams. Surface roughness and defects in AM materials were examined, and surface treatment was applied to improve surface quality. The machined specimens showed the highest fatigue properties regardless of load sequence by improving both the roughness and removing the contour layer containing the highest density of defect. The impact of corrosion was more pronounced for as-printed specimens as slightly deeper pits were formed, which lowered the fatigue-corrosion life. As discussed, the corrosion, fatigue and fatigue-corrosion mechanisms were strongly related to the local microstructure and existing defects in the AM sample. [ABSTRACT FROM AUTHOR]

To address the issues of low detection accuracy, slow detection speed, high missed detection rate, and high false detection rate in the detection of surface defects on pre-impregnated composite materials during the automated tape laying and winding process, an improved YOLOv5 (You Only Look Once version 5) algorithm model was proposed to achieve the high-precision, real-time detection of surface defects. By leveraging this improvement, the necessity for frequent manual interventions, inspection interventions, and subsequent rework during the automated lay-up process of composite materials can be significantly reduced. Firstly, to improve the detection accuracy, an attention mechanism called "CA (coordinate attention)" was introduced to enhance the feature extraction ability, and a Separate CA structure was used to improve the detection speed. Secondly, we used an improved loss function "SIoU (SCYLLA-Intersection over Union) loss" to replace the original "CIoU (Complete-Intersection over Union) loss", which introduced an angle loss as a penalty term to consider the directional factor and improve the stability of the target box regression. Finally, Soft-SIoU-NMS was used to replace the original NMS (non-maximum suppression) of YOLOv5 to improve the detection of overlapping defects. The results showed that the improved model had a good detection performance for surface defects on pre-impregnated composite materials during the automated tape laying and winding process. The FPS (frames per second) increased from 66.7 to 72.1, and the mAP (mean average precision) of the test set increased from 92.6% to 97.2%. These improvements ensured that the detection accuracy, as measured by the mAP, surpassed 95%, while maintaining a detection speed of over 70 FPS, thereby meeting the requirements for real-time online detection. [ABSTRACT FROM AUTHOR]

The endurance limit of structural mechanical components is affected by the residual stress state, which depends strongly on the manufacturing process. In general, compressive residual stresses tend to result in an increased fatigue strength. Post-manufacturing processes such as shot peening or vibratory finishing may achieve such a compressive residual stress state. But within complex components, manufacturing-process-based imperfections severely limit the fatigue strength. Thus, the interactions of imperfections, residual stress state and material strength are key aspects in fatigue design. In this work, cast steel and aluminium alloys are investigated, each of them in vibratory finished and polished surface condition. A layer-based fatigue assessment concept is extended towards stable effective mean stress state considering the elastic–plastic material behaviour. Murakami's concept was applied to incorporate the effect of hardness change and residual stress state. Residual stress relaxation is determined by elastic–plastic simulations invoking a combined hardening model. If the effective stress ratio within the local layer-based fatigue strength is evaluated as critical distance value, a sound calculation of fatigue strength can be achieved. Summing up, the layer-based fatigue strength design is extended and features an enhanced understanding of the effective stabilized mean stress state during cyclic loading. [ABSTRACT FROM AUTHOR]

Due to the high hardness and brittleness of ceramic materials, conventional cutting methods result in poor quality and machining difficulties. Additive manufacturing has also been tried in various ways, but it has many limitations. This study aims to propose a system to monitor surface defects that occur during the printing process based on high-viscosity composite resin that maximizes ceramic powder content in real time using image processing and convolutional neural network (CNN) algorithms. To do so, defects mainly observed on the surface were classified into four types by form: pore, minor, critical, and error, and the effect of each defect on the printed structure was tested. In order to improve the classification efficiency and accuracy of normal and defective states, preprocessing of images obtained based on cropping, dimensionality reduction, and RGB pixel standardization was performed. After training and testing the preprocessed images based on the DenseNet algorithm, a high classification accuracy of 98% was obtained. Additionally, for pore and minor defects, experiments confirmed that the defect surfaces can be improved through the reblading process. Therefore, this study presented a defect detection system as well as a feedback system for process modifications based on classified defects. [ABSTRACT FROM AUTHOR]

This study investigates the effect of electrolytic plasma processing on the degree of defective layer removal from a damaged layer obtained after manufacturing operations. Electrical discharge machining (EDM) is widely accepted in modern industries for product development. However, these products may have undesirable surface defects that may require secondary operations. This work aims to study the die-sinking EDM of steel components followed by the application of plasma electrolytic polishing (PeP) to enhance the surface properties. The results showed that the decrease in the roughness of the EDMed part after PeP was 80.97%. The combined process of EDM and subsequent PeP makes it possible to obtain the desired surface finish and mechanical properties. In the case of finishing EDM processing and turning, followed by PeP processing, the fatigue life is enhanced without failure up to 109 cycles. However, the application of this combined method (EDM + PeP) requires further research to ensure consistent removal of the unwanted defective layer. [ABSTRACT FROM AUTHOR]

A novel three-dimensional theoretical model of magnetic flux leakage (MFL) is proposed in this paper based on the magnetic dipole model. The magnetic dipole model assumes that a ferromagnetic specimen with defects is exposed to a uniform external magnetic field that causes a uniform magnetization around the defect surface. Under this assumption, the MFL can be regarded as arising from magnetic charges on the defect surface. Previous theoretical models were mostly used to analyze simple crack defects such as cylindrical and rectangular cracks. In this paper, we developed a magnetic dipole model for more complex defect shapes such as circular truncated holes, conical holes, elliptical holes, and double-curve-shaped crack holes to complement the existing defect shapes. Experimental results and comparisons with previous models demonstrate that the proposed model provides a better approximation of complex defect shapes. [ABSTRACT FROM AUTHOR]

Silicon heterojunction (SHJ) solar cells are increasingly attracting attention due to their low-temperature processing, lean steps, significant temperature coefficient, and their high bifacial capability. The high efficiency and thin wafer nature of SHJ solar cells make them ideal for use as high-efficiency solar cells. However, the complicated nature of the passivation layer and prior cleaning render a well-passivated surface difficult to achieve. In this study, developments and the classification of surface defect removal and passivation technologies are explored. Further, surface cleaning and passivation technologies of high-efficiency SHJ solar cells within the last five years are reviewed and summarized. [ABSTRACT FROM AUTHOR]

In order to improve the detection accuracy of the surface defect detection of industrial hot rolled strip steel, the advanced technology of deep learning is applied to the surface defect detection of strip steel. In this paper, we propose a framework for strip surface defect detection based on a convolutional neural network (CNN). In particular, we propose a novel multi-scale feature fusion module (ATPF) for integrating multi-scale features and adaptively assigning weights to each feature. This module can extract semantic information at different scales more fully. At the same time, based on this module, we build a deep learning network, CG-Net, that is suitable for strip surface defect detection. The test results showed that it achieved an average accuracy of 75.9 percent (mAP50) in 6.5 giga floating-point operation (GFLOPs) and 105 frames per second (FPS). The detection accuracy improved by 6.3% over the baseline YOLOv5s. Compared with YOLOv5s, the reference quantity and calculation amount were reduced by 67% and 59.5%, respectively. At the same time, we also verify that our model exhibits good generalization performance on the NEU-CLS dataset. [ABSTRACT FROM AUTHOR]

Chemical–mechanical planarization (CMP) represents the preferred technology in which both chemical and mechanical interactions are combined to achieve global planarization/polishing of wafer surfaces (wafer patterns from metal with a selective layer, in this paper). CMP is a complex process of material removal process by friction, which interferes with numerous mechanical and chemical parameters. Compared with chemical parameters, mechanical parameters have a greater influence on the material removal rate (MRR). The mechanical parameters manifest by friction force (Ff) and heat generated by friction in the CMP process. The Ff can be estimated by its monitoring in the CMP process, and process temperature is obtained with help of an infrared rays (IR) sensor. Both the Ff and the MRR increase by introducing colloidal silica (SiO2) as an abrasive into the selective layer CMP slurry. The calculated wafer non-uniformity (WNU) was correlated with the friction coefficient (COF). The control of Ff and of the slurry stability is important to maintain a good quality of planarization with optimal results, because Ff participates in mechanical abrasion, and large Ff may generate defects on the wafer surface. Additionally, the temperature generated by the Ff increases as the SiO2 concentration increases. The MRR of the selective layer into the CMP slurry showed a non-linear (Prestonian) behavior, useful not only to improve the planarization level but to improve its non-uniformity due to the various pressure distributions. The evaluation of the Ff allowed the calculation of the friction energy (Ef) to highlight the chemical contribution in selective-layer CMP, from which it derived an empirical model for the material removal amount (MRA) and validated by the CMP results. With the addition of abrasive nanoparticles into the CMP slurry, their concentration increased and the MRA of the selective layer improved; Ff and MRR can be increased due to the number of chemisorbed active abrasive nanoparticles by the selective layer. Therefore, a single abrasive was considered to better understand the effect of SiO2 concentration as an abrasive and of the MRR features depending on abrasive nanoparticle concentration. This paper highlights the correlation between friction and temperature of the SiO2 slurry with CMP results, useful to examine the temperature distribution. All the MRRs depending on Ef after planarization with various SiO2 concentrations had a non-linear characteristic. The obtained results can help in developing a CMP process more effectively. [ABSTRACT FROM AUTHOR]

Concrete surface defects are very complex and diverse, which is a great test for repair materials. The efficiency and durability of the repair system depend on the bonding effect between the concrete and the repair material. However, the rapid increase in system viscosity during the reaction of repair materials is an important factor affecting the infiltration effect. In the present work, the infiltration consolidation repair material was prepared, and its basic properties (viscosity, surface drying time and actual drying time, infiltration property) and mechanical properties were evaluated. Finally, the infiltration depth, film-forming thickness, and anti-spalling ability of concrete under a single-side freeze–thaw cycle are revealed. The results showed that using ethyl acetate could rapidly reduce the viscosity of the repair material, and the repair material could penetrate 20–30 mm into the concrete within 10 min. It was found by laser confocal microscopy that the thickness of the film formation after 3 days was only 29 µm. In the mortar fracture repair test to evaluate the bond strength, the bond strength of the repaired material reached 9.18 MPa in 28 days, and the new fracture surface was in the mortar itself. In addition, the freeze–thaw cycle test was carried out on the composite specimens under salt solution to verify the compatibility of the designed repair material with the concrete substrate. The data showed that the average amount of spalling was only 1704.4 g/m2 when 10% ethyl acetate was added. The penetrating repair material in this study has good infiltration performance, which can penetrate a certain depth in the surface pores and form a high-performance consolidation body, forming a "rooted type" filling. [ABSTRACT FROM AUTHOR]

The application of Nb microalloying to high-carbon pearlite bridge cable wire rod steel has always been controversial, especially in the actual production process, which will be affected by the cooling rate, holding temperature and final bonding temperature. In this paper, the experimental characterization, finite element simulation and phase diagram calculation of the test steel were carried out, then the microstructure and properties of different parts of Nb microalloying of bridge cable wire rods were compared and analyzed. The phase transition interval of pearlite during the water-cooling process of bridge cable wire rods is increased due to the refinement of austenite grains, and the significant increase in the end temperature of the phase transition makes the average interlamellar spacing of pearlite increase. The cooling rate of different parts of bridge cable wire rods simulated by Abaqus has little difference. At the same time, Nb microalloying effectively increases the proportion of low-angle grain boundaries, so that the overall average misorientation representing the surface defects is reduced. This helps to reduce the surface energy and increase the stability of the microstructure. Combined with the mechanical properties of microtensile rods, it is found that the grain refinement effect of Nb is greater than that of coarsening interlamellar spacing during hot rolling deformation in actual production, which makes the tensile strength at the 1/4 section increase significantly. The overall tensile strength and area shrinkage of the steel wire have also been effectively improved. [ABSTRACT FROM AUTHOR]

The constant effort of all metal alloy manufacturing technologies and processes is to improve the resulting quality of the processed part. Not only the metallographic structure of the material is monitored, but also the final quality of the cast surface. In foundry technologies, in addition to the quality of the liquid metal, external influences, such as the behaviour of the mould or core material, significantly affect the cast surface quality. As the core is heated during casting, the resulting dilatations often lead to significant volume changes causing stress foundry defects such as veining, penetration and surface roughness. In the experiment, various amounts of silica sand were replaced with artificial sand and a significant reduction in dilation and pitting of up to 52.9% was observed. An important finding was the effect of the granulometric composition and grain size of the sand on the formation of surface defects from brake thermal stresses. The specific mixture composition can be considered as an effective prevention against the formation of defects instead of using a protective coating. [ABSTRACT FROM AUTHOR]

The surfaces of cold-rolled titanium-containing ferrite stainless steel (TCFSS) strips produced from scrap are prone to severe peeling owing to cracking near slab inclusions during hot rolling. In this study, the Taguchi method was used to prevent peeling defects and clogging of the submerged entrance nozzle, and the optimal casting parameters, such as the degree of casting overheating, casting speed, stirring time, and inclination, were determined. The results showed that increasing the degree of casting overheating and decreasing the casting speed prevented clogging and effectively mitigated peeling defects. Sample A3B1C3D2 had the optimal parameters to reduce the clog thickness to less than 1.5 mm, i.e., a degree of overheating of 60 °C, a casting speed of 0.80 m/min, a stirring time of 12.0 s, and an inclination angle of 6.0°. Sample A3B1C1D3 had the optimal parameters to prevent peeling defects, i.e., a degree of overheating of 60 °C, a casting speed of 0.80 m/min, a stirring time of 10.0 s, and an inclination angle of 6.2°. When casting using these optimal parameters, no peeling defects were observed on the surfaces of the TCFSS strips. The TCFSS strips produced using the optimized parameters exhibited the required mechanical properties and satisfied the design criteria. The parameters included a tensile strength of ≥415 MPa, a yield strength of ≥205 MPa, an elongation of ≥22%, and a hardness of ≤89 HRB. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the fatigue properties of C17200 alloy under the condition of quenching aging heat treatment at high temperatures, and to provide a design reference for its application in a certain temperature range. For this purpose, the tensile and rotary bending fatigue (RBF) tests were carried out at different temperatures (25 °C, 150 °C, 350 °C, and 450 °C). The tensile strength was obtained, and relationships between the applied bending stress levels and the number of fatigue fracture cycles were fitted to the stress-life (S-N) curves, and the related equations were determined. The fractured surfaces were observed and analyzed by a scanning electron microscopy (SEM). The results show that the RBF fatigue performance of C17200 alloy specimens is decreased with the increase in test temperature. When the temperature is below 350 °C, the performance degradation amplitudes of mechanical properties and RBF fatigue resistance are at a low level. However, compared to the RBF fatigue strength of 1 × 107 cycles at 25 °C, it is decreased by 38.4% when the temperature reaches 450 °C. It is found that the fatigue failure type of C17200 alloy belongs to surface defect initiation. Below 350 °C, the surface roughness of the fatigue fracture is higher, which is similar to the brittle fracture, so the boundary of the fracture regions is not obvious. At 450 °C, due to the further increase in temperature, oxidation occurs on the fracture surface, and the boundary of typical fatigue zone is obvious. [ABSTRACT FROM AUTHOR]

Despite the remarkable capabilities of friction stir welding (FSW) in joining dissimilar materials, the numerical simulation of FSW is predominantly limited to the joining of similar materials. The material mixing and defects' prediction in FSW of dissimilar materials through numerical simulation have not been thoroughly studied. The role of progressive tool wear is another aspect of practical importance that has not received due consideration in numerical simulation. As such, we contribute to the body of knowledge with a numerical study of FSW of dissimilar materials in the context of defect prediction and tool wear. We numerically simulated material mixing and defects (surface and subsurface tunnel, exit hole, and flash formation) using a coupled Eulerian–Lagrangian approach. The model predictions are validated with the experimental results on FSW of the candidate pair AA6061 and AZ31B. The influence of tool wear on tool dimensions is experimentally investigated for several sets of tool rotations and traverse speeds and incorporated in the numerical simulation to predict the weld defects. The developed model successfully predicted subsurface tunnel defects, surface tunnels, excessive flash formations, and exit holes with a maximum deviation of 1.2 mm. The simulation revealed the substantial impact of the plate position, on either the advancing or retreating side, on the defect formation; for instance, when AZ31B was placed on the AS, the surface tunnel reached about 50% of the workpiece thickness. The numerical model successfully captured defect formation due to the wear-induced changes in tool dimensions, e.g., the pin length decreased up to 30% after welding at higher tool rotations and traverse speeds, leading to surface tunnel defects. [ABSTRACT FROM AUTHOR]

The main objective of this contribution was to determine the impact of magnesium (Mg) concentration and solidification rate (about 800 °C/s) on the mechanical properties of commercial A380.1 die-cast alloy. Respective amounts of 0.10%, 0.30%, and 0.50% Mg were used to establish their influence on the main tensile properties, namely, the ultimate limit, the elastic limit, and the percentage of elongation to fracture. The study also focused on the effect of magnesium on the fatigue behavior of A380.1 alloy where the role of surface defects and internal defects (porosity, oxide films, and inclusions) on the alloy fatigue life was also determined. The tensile properties were analyzed in order to optimize the heat treatments of T6 (under-aging) and T7 (over-aging). Consequently, the influence of several parameters was evaluated using tensile testing and optical and scanning electron micrography. Fatigue strength was investigated by performing rotational bending tests. The results show that the alloy tensile strength parameters improve with up to 0.3% Mg. Further addition of Mg, i.e., 0.5%, does not produce any significant improvement with respect to either traction or fatigue. It is observed that the tensile properties fluctuate according to the Guinier–Preston zones which occur during heat treatment, while the fatigue properties decrease as the Mg content increases. In contrast to a mechanical fatigue failure mechanism, in the present study, cracks were initiated at the sample's outer surface and then propagated toward the center. [ABSTRACT FROM AUTHOR]

Rare-earth orthoferrites have found wide application in thermocatalytic reduction-oxidation processes. Much less attention has been paid, however, to the production of CeFeO3, as well as to the study of its physicochemical and catalytic properties, in particular, in the promising process of CO2 utilization by hydrogenation to CO and hydrocarbons. This study presents the results of a study on the synthesis of CeFeO3 by solution combustion synthesis (SCS) using various fuels, fuel-to-oxidizer ratios, and additives. The SCS products were characterized by XRD, FTIR, N2-physisorption, SEM, DTA–TGA, and H2-TPR. It has been established that glycine provides the best yield of CeFeO3, while the addition of NH4NO3 promotes an increase in the amount of CeFeO3 by 7–12 wt%. In addition, the synthesis of CeFeO3 with the participation of NH4NO3 makes it possible to surpass the activity of the CeO2–Fe2O3 system at low temperatures (300–400 °C), as well as to increase selectivity to hydrocarbons. The observed effects are due to the increased gas evolution and ejection of reactive FeOx nanoparticles on the surface of crystallites, and an increase in the surface defects. CeFeO3 obtained in this study allows for achieving higher CO2 conversion compared to LaFeO3 at 600 °C. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study on the effectiveness of removing surface defects by brushing. Damage to machine components usually begins on their surface or in the surface layer area. This determines the development of methods, conditions, and process parameters that will positively affect the stereometric and physical properties of the surface layer. Experiments were conducted in which surface defects were generated on a specially designed test stand. By controlling the load and speed of the defect generator it was possible to affect the geometry, depth, and width of the surface defect. A FEM simulation of the brushing treatment was carried out in order to determine the effect of fibers passing through a surface defect in the form of a groove with a small depth and width. It was shown that for certain conditions of brushing treatment, surface defects could be removed effectively. Moreover, the microhardness of the surface layer after the brushing process was analyzed. Changes in microhardness due to brushing reached up to 50 μm for EN AW-2024 aluminum alloy and up to 150 μm for AZ91HP magnesium alloy. The results demonstrated that brushing was an effective method for strengthening the surface layer and that the value of strengthening in the area of defects depended on the effectiveness of their removal. [ABSTRACT FROM AUTHOR]

In this study, the axial fatigue behaviour of hot forging tool steels at room temperature was investigated. Fatigue tests were performed on two steels within the same H13 specification. The fatigue tests were carried out in the high-cycle fatigue domain under normal conditions. These tests were also performed on specimens in contact with a corrosive medium, applying stress values that led to the high-cycle fatigue domain under normal conditions for the sake of comparison. Both materials showed similar fatigue strengths when they were tested under normal conditions. In contrast, corrosion fatigue lives were much lower than in normal tests and differed significantly between the two steels. Crack initiation was triggered by microstructural and surface defects in the normal tests, whereas the formation of corrosion pits caused crack initiation in the corrosion fatigue tests. Moreover, a fracture surface analysis revealed dissimilar crack propagation areas between both steels, which suggested that both steels had different fracture toughness. These results were in line with the differences observed between the carbide and grain sizes of both of the material microstructures. [ABSTRACT FROM AUTHOR]

Multi-layered NiO nanowires linked with a nitrogen-doped carbon backbone grown directly on flexible carbon cloth (NiO/NCBN/CC) was successfully fabricated with a facile synthetic strategy. The NiO/NCBN/CC was further used as a binding-free electrode for flexible energy storage devices, showing a boosted performance including a high capacitance of 1039.4 F g−1 at 1 A g−1 and an 83.4% capacitance retention ratio. More importantly, after 1500 cycles, the capacitance retention can achieve 72.5% at a current density of 20 A g−1. The excellent electrochemical properties of the as-prepared NiO/NCBN/CC are not only attributed to the multi-layered structure that can help to tender unimpeded channels and accommodate the electrolyte ions around the electrode interface during the charge–discharge process, but is also due to the link between the NiO and N-doped carbon backbone and the nitrogen doping on the carbon substrate, which results in extra defects on the surface that could boost the interfacial electron transfer rate of the electrode. [ABSTRACT FROM AUTHOR]

This work analyses the microstructural defects and the corrosion behaviour of 316L stainless steel clads deposited by laser metal deposition on wrought conventional material, which is a highly relevant system for repair applications. The different defects and microstructural features found in these systems were identified and analysed from a perspective relevant to the corrosion performance of these materials. The role of these features and defects on the corrosion process was evaluated by exposure of the samples to corrosive media and further examination of the corrosion morphology. The heat-affected zone, located on the wrought base material in close vicinity of the deposited clad, was identified to be the primary contributor to the corrosion activity of the system due to the large depletion of alloying elements in this region, which significantly decreased its pitting resistance. Alongside the heat-affected zones, relatively small (<30 µm in diameter) partially un-melted powder particles scattered across the surface of the clad were systematically identified as corrosion initiation spots, possibly due to their relatively high surface energy and therefore high reactivity compared to larger powder particles. This work highlights the need for more investigations on as-built surfaces of additively manufactured parts to better explore/understand the performance of the materials closer to their final applications. It demonstrates that the surface defects resulting from the additive manufacturing process, rather than the presence of the refined sub-granular cellular structure (as highlighted in previous works), play the predominant role in the corrosion behaviour of the system. [ABSTRACT FROM AUTHOR]

Surface deformation is a multi-factor, laser powder-bed fusion (LPBF) defect that cannot be avoided entirely using current monitoring systems. Distortion and warping, if left unchecked, can compromise the mechanical and physical properties resulting in a build with an undesired geometry. Increasing dwell time, pre-heating the substrate, and selecting appropriate values for the printing parameters are common ways to combat surface deformation. However, the absence of real-time detection and correction of surface deformation is a crucial LPBF problem. In this work, we propose a novel approach to identifying surface deformation problems from powder-bed images in real time by employing a convolutional neural network-based solution. Identifying surface deformation from powder-bed images is a significant step toward real-time monitoring of LPBF. Thirteen bars, with overhangs, were printed to simulate surface deformation defects naturally. The carefully chosen geometric design overcomes problems relating to unlabelled data by providing both normal and defective examples for the model to train. To improve the quality and robustness of the model, we employed several deep learning techniques such as data augmentation and various model evaluation criteria. Our model is 99% accurate in identifying the surface distortion from powder-bed images. [ABSTRACT FROM AUTHOR]

An analysis of our data on 1H and 13C spin–lattice and spin–spin relaxation times and rates in aqueous suspensions of purified nanodiamonds produced by detonation technique (DNDs), DNDs with grafted paramagnetic ions, and micro- and nanodiamonds produced by milling bulk high-temperature high-pressure diamonds is presented. It has been established that in all the studied materials, the relaxation rates depend linearly on the concentration of diamond particles in suspensions, the concentration of grafted paramagnetic ions, and surface paramagnetic defects produced by milling, while the relaxation times exhibit a hyperbolic dependence on the concentration of paramagnetic centers. This is a universal law that is valid for suspensions, gels, and solids. The results obtained will expand the understanding of the properties of nano- and microdiamonds and will be useful for their application in quantum computing, spintronics, nanophotonics, and biomedicine. [ABSTRACT FROM AUTHOR]

Nanocomposites based on iron oxide/titanium oxide nanoparticles were prepared by employing green synthesis, which involved phytochemical-mediated reduction using ginger extract. XRD confirmed the composite formation, while scanning electron microscopy (SEM), dynamic light scattering (DLS), and energy-dispersive X-ray spectroscopy (EDX) was employed to investigate the particle size, particle morphology, and elemental analysis. SEM indicated the formation of particles with non-uniform shape and size distribution, while EDX confirmed the presence of Fe, Ti and oxygen in their elemental state. The surface effects were investigated by Fourier transform infrared radiation (FTIR) and impedance spectroscopy (IS) at room temperature. IS confirmed the co-existence of grains and grain boundaries. Thus, FTIR and IS analysis helped establish a correlation between enhanced surface activity and the synthesis route adopted. It was established that the surface activity was sensitive to the synthesis route adopted. The sample density, variation in grain size, and electrical resistivity were linked with surface defects, and these defects were related to temperature. The disorder and defects created trap centers at the sample's surface, leading to adsorption of CO2 from the environment. [ABSTRACT FROM AUTHOR]

Ceramic coatings were prepared by plasma electrolytic oxidation (PEO) on four different surface roughness' of Ti-6Al-4V alloys. The effects of substrate roughness on the microstructure and fatigue behavior were investigated. Microstructural characterization was carried out by scanning electron microscopy (SEM) and a laser scanning confocal microscope. In addition, an X-ray diffractometer (XRD) and a U-X360 stress meter were used to analyze the phase composition and residual stress properties of the coatings. The microstructure of coatings revealed the growth mechanism of the coatings. The larger and deeper grooves of the substrate promoted the nucleation and growth of the PEO coating, but the defects (cracks and pores) of the oxide layer became more serious. The fatigue test indicated a significant influence of substrate roughness on the fatigue life under low cyclic stress. The fatigue damage of PEO coatings decreases as the surface roughness of substrates decreases because of the synergistic effect of the coating surface defects and coating/substrate interface roughness. Substrate roughness influences the quality and fatigue performance of the oxide layer. [ABSTRACT FROM AUTHOR]

Magnesium alloys have been widely used as lightweight engineering structural materials, but their service performances are severely restricted by corrosion failure. In this paper, the influence of corrosive medium and surface defect energy on the corrosion behavior of rolled ZK61M alloy was investigated. The corrosion tests were conducted in different concentrations of sodium chloride solution for different durations, and the polarization curves and electrochemical impedance spectroscopy were reported. The surface morphology of rolled ZK61M alloy before and after corrosion tests were analyzed. The results showed that the corrosion tendency became stronger with the increase of the concentration of corrosive medium and the number of surface defects of ZK61M alloy. Moreover, the initial corrosion pattern was the pitting caused by micro galvanic corrosion at the surface defect, which gradually developed into uniform corrosion. Furthermore, the main damage occurred at the grain boundary, resulting in the destruction of grain bonding force and the removal of material along the rheological layer. The oxidation corrosion mechanism was mainly the anodic dissolution mechanism. [ABSTRACT FROM AUTHOR]

In recent decades, extensive research has been performed on the friction stir welding of flat-shaped materials while pipe welding, particularly polymer pipes, still encounters challenging issues. This work presents a feasible route for joining high-density polyethylene (HDPE) pipes using an orbital friction stir welding (OFSW) set-up properly designed with a retractable pin tool. Fully consolidated joints were achieved using a portable heating-assisted OFSW system suited for on-site pipeline welding. The obtained joined pipes were characterized by a high-quality weld surface and a lack of defects arising from the tool-pin hole. The samples welded with the optimum parameters presented comparable properties with the base materials and even a slight increase in the tensile strength. The highest tensile and impact strengths were 14.4 MPa and 2.45 kJ/m2, respectively, which is 105% and 89% of those of the base material. XRD, FTIR, and SEM were also applied to assess the property changes in the HDPE pipes after the FSW process. The morphological analysis evidenced that the crystalline structure of the welded sample was similar to that of the base material, proving the effectiveness of the proposed technology. [ABSTRACT FROM AUTHOR]

Aluminum alloy (Al6061-T6) is an alloy with strong corrosion resistance, excellent disassembly, and moderate strength, which is widely used in the fields of construction, automobile, shipping, and aerospace manufacturing. Researching on the influence of machining precision and surface quality on the micro-milling process of thin-walled structures of Al6061 is highly significant. Combined with the two simulations (DEFORM-3D simulation and interactive finite element numerical simulation (FEM)) and milling experimental verification, the deformations, errors, and surface quality of milling thin-walled Al6061 were analyzed. The simulations and experimental results show that the deformation of milling a micro thin-walled structure was caused by the vertical stiffness of the thin-walled structure and the cutting force. Surface micromorphology further characterized and showed a poorer quality area, top burr, and concave defects, which directly affect machining quality. It is necessary to improve the surface quality, reduce the surface defects, and increase the stiffness at the top of thin-walled structures in future work. [ABSTRACT FROM AUTHOR]

Robotic milling has broad application prospects in many processing fields. However, the milling performance of a robot in a certain posture, such as in face milling or grooving tasks, is extremely sensitive to process parameters due to the influence of the serial structure of the robot system. Improper process parameters are prone to produce machining defects such as low surface quality. These deficiencies substantially decrease the further application development of robotic milling. Therefore, this paper selected a certain posture and carried out the robotic flat-end milling experiments on a 7075-T651 high-strength aeronautical aluminum alloy under dry conditions. Milling load, surface quality and vibration were selected to assess the influence of process parameters like milling depth, spindle speed and feed rate on the milling performance. Most notably, the contribution ratio based on the analysis of variance (ANOVA) was introduced to statistically investigate the relation between parameters and milling performance. The obtained results show that milling depth is highly significant in milling load, which had a contribution ratio of 69.25%. Milling depth is also highly significant in vibration, which had a contribution ratio of 51.41% in the X direction, 41.42% in the Y direction and 75.97% in the Z direction. Moreover, the spindle speed is highly significant in surface roughness, which had a contribution ratio of 48.02%. This present study aims to quantitatively evaluate the influence of key process parameters on robotic milling performance, which helps to select reasonable milling parameters and improve the milling performance of the robot system. It is beneficial to give full play to the advantages of robots and present more possibilities of robot applications in machining and manufacturing. [ABSTRACT FROM AUTHOR]