Black Spot Defects Research Articles

Study on the formation and corrosion mechanism of black spot defects on the surface of industrial continuously hot-dip galvanized Zn-2Al-1.5Mg coating

Study on the formation and corrosion mechanism of black spot defects on the surface of industrial continuously hot-dip galvanized Zn-2Al-1.5Mg coating

Defect Analysis of Packaging Bottle Products Using Six Sigma and Kaizen Methods at PT. XYZ

PT XYZ is a company engaged in manufacturing plastic packaging. The company produces various forms of packaging, one of which is cosmetic bottle packaging. Meanwhile, based on the problems of the production process, various types of product defects such as black spots, leaks, and oil dirt are often found. The company produces the most defective products in 30ml cosmetic bottle products, with a percentage of 3% to 4% of the total production. Based on the above problems, this study aims to determine the level of defects and the sigma value of product quality. In addition, provide suggestions for improvement to reduce the level of product defects at PT XYZ. The methods used are Six sigma and Kaizen. The Six Sigma stages include define, measure, analyze, and improve. The improve stage is assisted by the Kaizen Five M Checklist and Kaizen Five Step Plan. The improve stage is assisted by the Kaizen Five M Checklist and Kaizen Five Step Plan. Based on the results of research with the six sigma method, the percentage of black spot defects is 74%, leaking is 14.1%, and dirty oil is 11.9%. the proposed improvements given are providing 5S training and SOP refreshment, sorting reject products before grinding, cleaning the machine and production area at the end of each shift, replacing blowpin threads and bolts, and others.

Surface Defect Detection of Bearing Rings Based on an Improved YOLOv5 Network.

Considering the characteristics of complex texture backgrounds, uneven brightness, varying defect sizes, and multiple defect types of the bearing surface images, a surface defect detection method for bearing rings is proposed based on improved YOLOv5. First, replacing the C3 module in the backbone network with a C2f module can effectively reduce the number of network parameters and computational complexity, thereby improving the speed and accuracy of the backbone network. Second, adding the SPD module into the backbone and neck networks enhances their ability to process low-resolution and small-object images. Next, replacing the nearest-neighbor upsampling with the lightweight and universal CARAFE operator fully utilizes feature semantic information, enriches contextual information, and reduces information loss during transmission, thereby effectively improving the model's diversity and robustness. Finally, we constructed a dataset of bearing ring surface images collected from industrial sites and conducted numerous experiments based on this dataset. Experimental results show that the mean average precision (mAP) of the network is 97.3%, especially for dents and black spot defects, improved by 2.2% and 3.9%, respectively, and that the detection speed can reach 100 frames per second (FPS). Compared with mainstream surface defect detection algorithms, the proposed method shows significant improvements in both accuracy and detection time and can meet the requirements of industrial defect detection.

Machine Learning-Augmented Micro-Defect Detection on Plastic Straw

Plastic straws are well-known tools to assist human beings in drinking fluid, but most of them have micro-defects including black spot defects, head problems, pressure tube defects, and sealing wrinkles. The manual detection of these defects has drawbacks such as low efficiency, a high false detection rate, and excessive labor. This paper proposed machine vision-based detection with self-adaption and high-accuracy characteristics. A serial synthesis of algorithms including homomorphic filtering, Nobuyuki Otsu, and morphological opening operations is proposed to obtain plastic straws with binary images with good performance, and it was further found that the convolutional neural network can be designed to realize the real-time recognition of black spot defects, where the corner detection algorithm demonstrates the linear fitting of the edge point of the straw with the effective detection of sealing wrinkle defects. We also demonstrated that the multi-threshold classification algorithm is used to detect defects effectively for head problems and pressure tube defects. The detection system based on machine vision successfully overcomes shortcomings of manual inspection, which has high inspection efficiency and adaptively detects multiple defects with 96.85% accuracy. This research can effectively help straw companies achieve high-quality automated production and promotes the application of machine vision in plastic straw defects with the aid of machine learning.

Damage in Xe-implanted 4H-SiC under severe conditions

Xenon ions were implanted in 4H-SiC at 400 and 700 °C with fluences of 1 × 1016 and 3 × 1016 cm−2, respectively. Transmission Electron Microscopy (TEM) experiments were carried out to study the resulting microstructure and its evolution after a 1400 °C annealing. Observations show that the temperature of implantation plays an active role in the formation of as-generated defects. The implantation temperature of 400 °C is too low to allow the formation of visible defects and only a strongly damaged band is observed in the ion stopping range. The post-implantation annealing results in the formation of nanometric cavities along the ion path. In the buried ion stopping region, xenon solid cavities or nano-precipitates of about 10 nm in diameter are present. Other types of defects were also formed during annealing, a high density of stacking faults is observed among the solid cavities and black spot defects are observed beyond the implanted area. At a temperature of 700 °C, the vacancies become mobile enough to cause the formation of nanocavities all along the ions path, i.e. voids in the near surface region and full-gas cavities in the xenon stopping range. At this temperature stacking faults were also formed as well as the defect band at the back. The annealing only causes a slight growth of the solid cavities.

Characterization and control of a new kind of black spot defects on surface of hot-dip galvanized low-aluminum Zn-1.5Al-1.1 Mg coatings

Surface defects can seriously affect the appearance and performance of Zn-Al-Mg coatings. In this work, a new kind of black spot defects on the surface of hot-dip galvanized low-aluminum Zn-1.5Al-1.1 Mg coatings were investigated. Results revealed that the microstructures of normal and black spot regions were both composed of primary Zn, Zn/MgZn2 binary eutectic (BE) and Zn/MgZn2/Al ternary eutectic (TE). This kind of black spots with a diameter of 1 μm were caused by the difference in light reflection with normal region after generating local pseudo-eutectic structures. When the solidification cooling rate was controlled to 18 °C/s, the black spot defects were completely eliminated. Furthermore, the corrosion current density was reduced to 1.2 μA/cm2 and the coating resistance increased to 2427 Ω·cm2 in 3.5 wt% NaCl solution.

In-situ observation of damage structure in Cu-Cr-Zr and Cu-Cr alloy during 1.25 MeV electron irradiation

The sink strengths of precipitate/matrix interfaces in Cu alloys, were investigated by performing in-situ observation of electron irradiation in high-voltage electron microscopy (HVEM). Fine black spot defects, which seemed to be dislocation loops were observed at irradiation temperature ranging between RT and 373 K in Cu–Cr–Zr, Cu–Cr and GlidCop Al–60 alloys with low number density. In Cu–Cr, loops formed on a part of precipitates interfaces. Hence, a part of precipitate/matrix interfaces is a sink with interstitial bias. Whereas, most of the interfaces are neutral sinks for point defects. In the case of Cu–Cr–Zr and GlidCop Al–60, black spots formed around dislocation, which were induced during two-step heat treatment. The results showed that the precipitate/matrix interface of Cr-rich precipitates in Cu alloys serve as a strong sink for point defects.

Radiation damage analysis in SiC microstructure by transmission electron microscopy

Microstructures of monolithic high purity SiC and SiC with sintering additives after neutron irradiation to a fluence of 2.0–2.5 × 1024 n/m2 (E > 0.1 MeV) at 333–363 K and after post-irradiation annealing up to 1673 K were observed using a transmission electron microscopy. Results showed that no black spot defects or dislocation loops in SiC grains were found after the neutron irradiation for all of the specimens owing to the moderate fluence at low irradiation temperature. Thus, it is confirmed that these specimens were swelled mostly by the formation of point defects. Black spots and small dislocation loops were discovered only after the annealing process in PureBeta-SiC and CVD-SiC, where the swelling almost diminished. Anomalous-shaped YAG grains were found in SiC ceramics containing sintering additives. These grains contained dense black spots defects and might lose crystallinity after the neutron irradiation, while these defects may annihilate by recrystallization during annealing up to 1673 K. Amorphous grain boundary phase was also presented in this ceramic, and a large part of it was crystallized through post-irradiation annealing and could affect their recovery behavior.

Electron energy-loss spectroscopic evaluation of depth-dependent swelling of He+ ion-irradiated 4H-SiC correlated with defect type

Various defects and amorphous transitions are the primary mechanism behind the accumulation of swelling in silicon carbide (SiC). In this study, selected-area He+ ion irradiation was carried out on single-crystal 4H-SiC using fluences of 1 × 1015, 5 × 1016, and 1 × 1017 cm−2 at room temperature. The defect distribution in the samples with varying irradiation fluences was analyzed using transmission electron microscopy (TEM), while the local swelling of regions under varying damage conditions was estimated using electron energy-loss spectroscopy. The results provide the range of swelling in SiC possessing different primary defect types, such as point defects or tiny clusters, black spot defects, and amorphous SiC. A saturation swelling with a value of 2%–3% in the near-surface region, induced by point defects or tiny clusters (invisible in TEM), was observed at room temperature over the fluence range of 1 × 1015 to 1 × 1017 cm−2. This saturation has already reached at a great low dose of about 0.02 dpa. The swelling of the region containing black spot defects ranges from about 3% to 7%. Helium bubbles increase the volume swelling of SiC, while the He+ ion irradiation may also perform a decreasing effect on the volume swelling below a certain irradiation fluence.

Multi-axial and multi-energy channeling study of disorder evolution in ion-irradiated nickel

To better understand defect structure and the evolution of irradiation-induced damage in single crystal Ni, in situ Rutherford backscattering spectroscopy in channeling geometry (RBS/C) is performed along the <100>, <110>, and <211> axes with different probing beam energies. The RBS/C data reveal that damage evolution occurs in three steps. The first step at low doses (up to 0.2 dpa), characterized by a linear increase with dose, is related to the formation of point defects and small clusters. The second step in the intermediate dose range (0.2–1.0 dpa) shows a sublinear increase in disorder to saturation. This sublinear increase is due to the growth of defect clusters resulting from the interaction of irradiation-induced defects with already existing damage from previous ion impacts. The third step at high doses (1.0–32.4 dpa) exhibits a surprising decrease in the disorder level, which may be attributed to defect evolution from black spot defects to large dislocation loops that leads to strain relaxation. In addition, the damage extends much deeper than the predicted depths and is attributed to long-range defect migration effects confirmed by transmission electron microscopy (TEM) observations. Although similar damage evolution trends have been observed along all channeling directions, the disorder accumulation is largest along the <100> and <211> axes than observed along <110> axis. This “preferential” disordering process along <100> and <211> suggests that more defects are shielded by the <110> atomic rows than the two other axes. The co-existence of both uncorrelated displaced lattice atoms and dislocation loops in Ni irradiated at 1 ion/nm2 is revealed by the energy-dependent RBS/C studies along all three axes. In contrast, dislocation loops and stacking fault tetrahedral are simultaneously present in the crystal structure of Ni irradiated at 100 ions/nm2 that is consistent with previous molecular dynamics simulations and TEM observations.

Massive α precipitation selectivity and tensile fracture behavior of TC18 alloy

Near β titanium alloys have been widely used for preparing the aerospace structure. However, the microstructure and mechanical properties are highly sensitive to the processing process. In the large size alloy bar, especially, the massive α phases precipitate in some β grain (black spot defects), which is not beneficial for improving the mechanical properties. In this paper, the analysis of β recrystallization and local α precipitation in TC18 alloy (near β alloy) has been carried out during the annealing. It is found that the massive α phases precipitate in β grains with stable-deformation orientations. The local massive α phases are responsible for forming the “black spots”. Compared with the alloy containing non-massive α, the strength of the alloy with the massive α apparently increases by the α precipitation strengthening, while the plasticity decreases greatly due to the crack propagation along the textured β grain or α lath/β interfaces within the normal grains. Based on the analysis of the relationship between the massive α and β orientations, the deformation dislocation storage energy induced α precipitation and tensile fracture mode have been further discussed.

合金化热镀锌带钢表面黑斑缺陷分析

合金化热镀锌带钢表面黑斑缺陷分析

Microscopic origin of black spot defect swelling in single crystal 3C-SiC

In this study, we perform a series of simulation of a high-energy particle irradiation on a 3C-SiC at low temperature through molecular dynamic analysis. In order to determine the formation mechanism of black spot defects (BSD), the evolution of defect clusters during the cascade process is examined. Simulation results show that there are more isolated interstitials scattering across the structure while the less mobile vacancies are concentrated in defect clusters, which is consistent with the depleted zone theory proposed by Brinkman [3]. These results also match the TEM observation and simulation results done by Lin et al. [4] and support the argument that black spot defects are in fact vacancy-rich regions, with individual interstitials spreading into bulk, stretching the lattice structure.

Atomic Configuration of Point Defect Clusters in Ion-Irradiated Silicon Carbide

Silicon Carbide (SiC) is a promising cladding material for accident-tolerant fuel in light water reactors due to its excellent resistance to chemical attacks at high temperatures, which can prevent severe accident-induced environmental disasters. Although it has been known for decades that radiation-induced swelling at low temperatures is driven by the formation of black spot defects with sizes smaller than 2 nm in irradiated SiC, the structure of these defect clusters and the mechanism of lattice expansion have not been clarified and remain as one of the most important scientific issues in nuclear materials research. Here we report the atomic configuration of defect clusters using Cs-corrected transmission electron microscopy and molecular dynamics to determine the mechanism of these defects to radiation swelling. This study also provides compelling evidence that irradiation-induced point defect clusters are vacancy-rich clusters and lattice expansion results from the homogenous distribution of unrecovered interstitials in the material.

Optimization of self-interstitial clusters in 3C-SiC with genetic algorithm

Under irradiation, SiC develops damage commonly referred to as black spot defects, which are speculated to be self-interstitial atom clusters. To understand the evolution of these defect clusters and their impacts (e.g., through radiation induced swelling) on the performance of SiC in nuclear applications, it is important to identify the cluster composition, structure, and shape. In this work the genetic algorithm code StructOpt was utilized to identify groundstate cluster structures in 3C-SiC. The genetic algorithm was used to explore clusters of up to ∼30 interstitials of C-only, Si-only, and Si-C mixtures embedded in the SiC lattice. We performed the structure search using Hamiltonians from both density functional theory and empirical potentials. The thermodynamic stability of clusters was investigated in terms of their composition (with a focus on Si-only, C-only, and stoichiometric) and shape (spherical vs. planar), as a function of the cluster size (n). Our results suggest that large Si-only clusters are likely unstable, and clusters are predominantly C-only for n ≤ 10 and stoichiometric for n > 10. The results imply that there is an evolution of the shape of the most stable clusters, where small clusters are stable in more spherical geometries while larger clusters are stable in more planar configurations. We also provide an estimated energy vs. size relationship, E(n), for use in future analysis.

Evolution of small defect clusters in ion-irradiated 3C-SiC: Combined cluster dynamics modeling and experimental study

Distribution of black spot defects and small clusters in 1 MeV krypton irradiated 3C-SiC has been investigated using advanced scanning transmission electron microscopy (STEM) and TEM. We find that two thirds of clusters smaller than 1 nm identified in STEM are invisible in TEM images. For clusters that are larger than 1 nm, STEM and TEM results match very well. A cluster dynamics model has been developed for SiC to reveal processes that contribute to evolution of defect clusters and validated against the (S)TEM results. Simulations showed that a model based on established properties of point defects (PDs) generation, reaction, clustering, and cluster dissociation, is unable to predict black spot defects distribution consistent with STEM observations. This failure suggests that additional phenomena not included in a simple point-defect picture may contribute to radiation-induced evolution of defect clusters in SiC and using our model we have determined the effects of a number of these additional phenomena on cluster evolution. Using these additional phenomena it is possible to fit parameters within physically justifiable ranges that yield agreement between cluster distributions predicted by simulations and those measured experimentally.

Size distribution of black spot defects and their contribution to swelling in irradiated SiC

Experimental and modeling efforts were combined to investigate the role of black spot defects (BSD) in swelling of carbon- and krypton-irradiated 4H-SiC. Samples were exposed to conditions favoring BSD formation: irradiation at temperatures 600–950 °C and damage levels of 0.4–0.8 dpa. The maximum XRD swelling values, corrected for the effect of the rigid substrate, of 0.58% for C and 0.75% for Kr-irradiation were measured at the lowest irradiation temperature of 600 °C and decreased with increasing temperature. The swelling values estimated from TEM are on the same order of magnitude, but usually 40–70% lower than those measured by XRD. The contribution of BSDs to the overall swelling is 62% and the remainder of the swelling is caused by isolated point defects. The obtained results contribute to understanding of what defect types account for swelling and how their concentration evolves with the irradiation temperature and damage level.

The nature of «black spots» formation on the surface of large parts made of aluminum alloys in the process of anodic oxidising

The causes of black spot defects detected on the surface of large parts made of aluminum alloys (D16chT, 1973T2, V95pchT2, V95pchT3) following anodic oxidation are investigated in the paper. A hypothesis of such defects appearing during the dissolution of intermetallics on the surface of a part in the process of etching during anodizing was put forward and tested. A technique was developed for this purpose the essence of which was that an intermetallic was detected on a polished sample and using a microhardness tester the area including the intermetallic was marked to facilitate its subsequent detection at the end of the specimen etching. After the etching of the specimen during periods of different duration in an alkaline bath of the anodizing line the area containing an intermetallic previously labeled using the microhardness tester was detected by microscopic observations and photographed. The duration of the etching process was 120 seconds and consisted of 8 cycles. Metallographic tests of the specimens. revealed the fact that in the process of etching of an aluminum alloy dissolution (etching) of intermetallic particles opening out on the surface of the part takes place. Subsequent anodic oxidation leads to the visualization of defects which have the form of black spots.

Atomic Resolution Imaging of Black Spot Defects in Ion Irradiated Silicon Carbide

Atomic Resolution Imaging of Black Spot Defects in Ion Irradiated Silicon Carbide

High-Resolution Scanning Transmission Electron Microscopy Study of Black Spot Defects in Ion Irradiated Silicon Carbide

High-Resolution Scanning Transmission Electron Microscopy Study of Black Spot Defects in Ion Irradiated Silicon Carbide