Quantitative Microstructural Analysis Research Articles

3D X-ray tomographic microstructure analysis of dust-clogging inside nonwoven fibrous filter media

Clogging inside fibrous filter media largely affects the particle loading characteristics of filter media. The three-dimensional (3D) analysis of particle deposits that form clogging is thus necessary. Compact nonwoven fibrous filter media with thick-fiber was fabricated using meltblown technology. Filter media with the deposited dust mass was scanned with X-ray μ-CT imaging. Methodology of image processing and image analysis was developed to open the black box of loaded fibrous filter media. Quantitative microstructure analysis was conducted including pristine fibrous structure analysis, quadrant structure analysis, depth distribution of particles, and size distribution of 3D particle deposits. Quadrant analysis revealed that deposited dust mass was negatively correlated with quadrant fiber solidity. A considerably large volume of particle deposits formed face-region (in the depth of 0–200 μm) clogging inside the filter structure. Higher-basis-weight filter media exhibited more particle deposition in deeper filter depth. Watershed-segmentation-based size distribution statistics revealed that more volume of large connected particle agglomerates and larger constituent individual particles existed inside higher-basis-weight filter media.

Deep learning based object tracking for 3D microstructure reconstruction.

In medical and material science, 3D reconstruction is of great importance for quantitative analysis of microstructures. After the image segmentation process of serial slices, in order to reconstruct each local structure in volume data, it needs to use precise object tracking algorithm to recognize the same object region in adjacent slice. Suffering from weak representative hand-crafted features, traditional object tracking methods always draw out under-segmentation results. In this work, we have proposed an adjacent similarity based deep learning tracking method (ASDLTrack) to reconstruct 3D microstructure. By transferring object tracking problem to classification problem, it can utilize powerful representative ability of convolutional neural network in pattern recognition. Experiments in three datasets with three metrics demonstrate that our algorithm achieves the promising performance compared to traditional methods.

Quantitative study on the microstructure of loess soils at micrometer scale via X-ray computed tomography

The macroscopic properties of loess soils are significantly controlled by their microstructure. However, researches on the microstructure of loess soils at micrometer scale are inadequate, especially in the aspect of quantitative analysis of three-dimensional (3D) microstructure. This study systematically investigates the micrometer-scale microstructure of loess soils from Jingyang, Shaanxi province, China, via X-ray computed tomography and explored image segmentation method. The microstructural characteristics, including size, shape, and arrangement of particle and pore, were discussed from the real 3D view and quantitatively analyzed by statistical method. Results showed that the representative elementary volume obtained through porosity is applicable to microstructural parameters of size distribution, shape factor, orientation angle, and pore connectivity. Sectional analysis revealed that the two-dimensional (2D) results of size, shape, arrangement, and pore connectivity cannot adequately represent the corresponding 3D characteristics. These works may provide insight for researches on the microstructure of similar particulate materials. • The micrometer-scale microstructure of loess soils was analyzed from real 3D view. • REV obtained from porosity is applicable to quantitative microstructure analysis. • 2D size, arrangement, shape, and pore connectivity cannot represent 3D characteristics.

Boundary learning by using weighted propagation in convolution network

In material science, image segmentation is of great significance for quantitative analysis of microstructures. Here, we propose a novel Weighted Propagation Convolution Neural Network based on U-Net (WPU-Net) to detect boundary in poly-crystalline microscopic images. We introduce spatial consistency into network to eliminate the defects in raw microscopic image. And we customize adaptive boundary weight for each pixel in each grain, so that it leads the network to preserve grain’s geometric and topological characteristics. Moreover, we provide our dataset with the goal of advancing the development of image processing in materials science. Experiments demonstrate that the proposed method achieves promising performance in both of objective and subjective assessment. In boundary detection task, it reduces the error rate by 7%, which outperforms state-of-the-art methods by a large margin.

Grain size analysis in permanent magnets from Kerr microscopy images using machine learning techniques

Understanding the relationships between composition, structure, processing and properties helps in the development of improved materials for known applications as well as for new applications. Materials scientists, chemists and physicists have researched these relationships for many years, until the recent past, by characterizing the bulk properties of functional materials and describing them with theoretical models. Magnets are widly used in electric vehicles (EV), hybrid electric vehicles (HEV), data storage, power generation and transmission, sensors etc. The search for novel magnetic phases requires an efficient quantitative microstructure analysis of microstructural information like phases, grain distribution and micromagnetic structural information like domain patterns, and correlating the information with intrinsic magnetic parameters of magnet samples. The information out of micromagnetic domains helps in obtaining the optimized microstructures in magnets that have good intrinsic magnetic properties. This paper is aimed at introducing the use of a traditional machine learning (ML) model with a higher dimensional feature set and a deep learning (DL) model to classify various regions in sintered NdFeB magnets based on Kerr-microscopy images. The obtained results are compared against reference data, which is generated manually by subject experts. Additionally, the results were compared against the approach for grain analysis, which is based on the electron backscatter diffraction (EBSD) technique. Further, the challenges faced by the traditional machine learning model for classifying microstructures in Kerr micrographs are discussed.

Experimental Investigation of the Biofunctional Properties of Nickel-Titanium Alloys Depending on the Type of Production.

Nickel–titanium alloys used in dentistry have a variety of mechanical, chemical, and biofunctional properties that are dependent on the manufacturing process. The aim of this study was to compare the mechanical and biofunctional performances of a nickel–titanium alloy produced by the continuous casting method (NiTi-2) with commercial nitinol (NiTi-1) manufactured by the classical process, i.e., from remelting in a vacuum furnace with electro-resistive heating and final casting into ingots. The chemical composition of the tested samples was analyzed using an energy dispersive X-ray analysis (EDX) and X-ray fluorescence (XRF). Electron backscatter diffraction (EBSD) quantitative microstructural analysis was performed to determine phase distribution in the samples. As part of the mechanical properties, the hardness on the surface of samples was measured with the static Vickers method. The release of metal ions (Ni, Ti) in artificial saliva (pH 6.5) and lactic acid (pH 2.3) was measured using a static immersion test. Finally, the resulting corrosion layer was revealed by means of a scanning electron microscope (SEM), which allows the detection and direct measurement of the formatted oxide layer thickness. To assess the biocompatibility of the tested nickel–titanium alloy samples, an MTT test of fibroblast cellular proliferation on direct contact with the samples was performed. The obtained data were analyzed with the IBM SPSS Statistics v22 software. EDX and XRF analyses showed a higher presence of Ni in the NiTi-2 sample. The EBSD analysis detected an additional NiTi2-cubic phase in the NiTi-2 microstructure. Additionally, in the NiTi-2 higher hardness was measured. An immersion test performed in artificial saliva after 7 days did not induce significant ion release in either group of samples (NiTi-1 and NiTi-2). The acidic environment significantly increased the release of toxic ions in both types of samples. However, Ni ion release was two times lower, and Ti ion release was three times lower from NiTi-2 than from NiTi-1. Comparison of the cells’ mitochondrial activity between the NiTi-1 and NiTi-2 groups did not show a statistically significant difference. In conclusion, we obtained an alloy of small diameter with an appropriate microstructure and better response compared to classic NiTi material. Thus, it appears from the present study that the continuous cast technology offers new possibilities for the production of NiTi material for usage in dentistry.

Evaluating the distinct identity and the orogen-scale nature of the Munsiari thrust in the Himalaya

The Munsiari thrust (MT) was first recognized in northwest India within the Paleoproterozoic Lesser Himalayan rocks, but debate persists over its distinct identity and orogen-scale nature. Some researchers have included the MT within a ∼3–10 km-wide Main Central thrust (MCT) zone, whereas others proposed that, it is the northern and deeper extension of the Ramgarh thrust (RT). This study integrates field mapping, quantitative microstructural analysis, grain-size measurement, and piezometry to evaluate the distinct identity of the MT from North Sikkim, in eastern Himalaya. Our study reveals the presence of a ∼1700 m-thick prominent shear zone showing thrust-sense motion. The mylonites in the ∼300 m-thick core of the shear zone deformed by DRX (dynamic recrystallization)-assisted dislocation creep, and by climb-assisted dislocation creep in the ∼400–1000 m-thick flanking zones. We infer the mapped shear zone represents Sikkim-equivalent of the MT, because it transported Paleoproterozoic Lesser Himalayan crystalline rocks over Paleoproterozoic Lesser Himalayan quartzites and phyllites. The MCT and the RT lie ∼6 km structurally above-and-below the MT respectively. By comparing our findings with published results, we infer that, the MT is an orogen-scale structure, traceable from northwest Himalaya to far-eastern Himalaya, and it facilitated rapid exhumation of the Lesser Himalayan crystalline rocks between mid-Miocene and Pliocene. Therefore, we propose to reserve the appellation of the “Munsiari thrust” for a shear zone that transported Paleoproterozoic Lesser Himalayan crystalline rocks over Lesser Himalayan quartzites and phyllites of similar age, and suggest not to confuse it with the MCT or the RT.

Microstructure-informed prediction and measurement of nanoindentation hardness of an Fe-9Cr alloy irradiated with Fe-ions of 1 and 5 MeV energy

Hardening of Fe-9%Cr alloys exposed to irradiation with Fe2+ ions of two different energies, 1 and 5 MeV, is investigated using nanoindentation. The limited penetration depth of the ions causes steep damage gradients in the near-surface volumes of the irradiated samples. This damage gives rise to graded microstructures resulting in depth-dependent irradiation hardening. Nanoindentation integrates the depth-dependent hardness over the indentation plastic zone. Our study combines quantitative analysis of the ion-irradiated microstructures with the determination of the full depth dependence of irradiation hardening. The microstructure-informed model incorporates direct experimental evidence revealed by a former investigation using cross-sectional scanning transmission electron microscopy. For both ion energies, the observed microstructures consist of dislocation loops with band-like distributions and are concluded to be the dominant source of the measured irradiation-induced hardening. The model predictions are found to be in reasonable agreement with the as-measured nanoindentation response. The comparison of hardening predictions with different kinds of superposition rules of hardening contributions suggests linear superposition as the most appropriate selection under the present conditions. The possible transferability of these results to neutron irradiation is also discussed.

Vat Photopolymerization of Cemented Carbide Specimen.

Numerous studies show that vat photopolymerization enables near-net-shape printing of ceramics and plastics with complex geometries. In this study, vat photopolymerization was investigated for cemented carbide specimens. Custom-developed photosensitive WC-12 Co (wt%) slurries were used for printing green bodies. The samples were examined for defects using quantitative microstructure analysis. A thermogravimetric analysis was performed to develop a debinding program for the green bodies. After sintering, the microstructure and surface roughness were evaluated. As mechanical parameters, Vickers hardness and Palmqvist fracture toughness were considered. A linear shrinkage of 26–27% was determined. The remaining porosity fraction was 9.0%. No free graphite formation, and almost no η-phase formation occurred. WC grain growth was observed. 76% of the WC grains measured were in the suitable size range for metal cutting tool applications. A hardness of 1157 HV10 and a Palmqvist fracture toughness of 12 was achieved. The achieved microstructure exhibits a high porosity fraction and local cracks. As a result, vat photopolymerization can become an alternative forming method for cemented carbide components if the amount of residual porosity and defects can be reduced.

New method for a SEM-based quantitative microstructural clay analysis - MiCA

The soil microstructure is recognised to strongly influence the mechanical behaviour of both coarse and fine geomaterials. Proper identification and tracking of the shape and position of the particles has become more and more critical to form a link between the micro and macro behaviour. Scanning Electron Microscopy (SEM) has been widely used in the last decades to study the clay fabric variation with its mechanical behaviour and physical properties. However, the particles orientation has so far been discussed only from a qualitative point of view due to the lack of updated, automatised quantification tools. Consequently, developing constitutive models that correlate the soil micro structure to its mechanical behaviour is not feasible. In order to make a step forward in this direction, an Image Analysis based code called MiCA (microstructural clay analyser) capable of quantifying the particle orientation and the porosity of clay samples through the analysis of SEM micrographs was developed in this study. The code reliability was first validated through the application to geometrical reference patterns, then to textbook micrographs illustrating typical clay fabrics (dispersed, honeycomb, flocculated and aggregated), and finally to high quality images. MiCA showed good accuracy in the results obtained, regardless of the number of lines in the image, the complexity of the geometrical shapes and the pixel size of the analysed graphs. Therefore, MiCA can be considered suitable for quantitative analysis of the particle orientation and/or pores shape in clay materials.

Microstructure beneath screen-printed silver contacts and its correlation to metallization-induced recombination parameters

In this work, we present an approach to model metallization-induced recombination losses j 0,met of screen-printed fire-through metallization pastes, which are used e.g. for the contacts on the front side of passivated emitter and rear cells (PERC). Modelling is based on the local phosphorus emitter doping profile and the local microstructure of the interface between metal contact and silicon surface, which is characterized during a quantitative microstructural analysis using the scanning electron microscope (SEM). By comparing the modelled j 0,met to measured j 0,met results determined at the same position of both, the microstructural analysis and emitter doping profile, we find that in most cases recombination is dominated by the etch back of the emitter by the glass frit rather than by penetration of crystallites into the doped region. However, for crystallites protruding deep into the emitter or rather up to the junction, recombination at the crystallites becomes significant as well. Our modelled results yield indications that the etch depth into the emitter doping profile by the glass frit contained in the metallization paste, is sensitive to the emitter doping profile itself. • Metallization-induced recombination is dominated by the etch back of the emitter doping profile • Etch back of the emitter doping profile is sensitive to doping profile itself • Plating useful to enhance contrast for microstructure analysis

Achieving high strength and ductility in equimolar FeMnNi medium entropy alloy by tuning microstructural entropy

Microstructural engineering approach was adopted to produce a multimodal recovered-recrystallized grain size distribution, in order to achieve optimum strength and ductility in equimolar FeMnNi medium entropy alloy (MEA). Detailed quantitative microstructure and micro-texture analysis using electron back scatter diffraction reveals the ability of the finer recovered grains to carry more stress and large recrystallized grains to impart ductility by promoting strain hardening. Furthermore, it was shown that the concept of microstructure entropy, a phenomenological parameter based on grain size distribution, provides a better prediction for the yield strength for heterogeneous microstructure compared to average grain size-based Hall-Petch model. Thus, the microstructural entropy model capturing the grain size distribution provides a robust methodology to establish structure – property correlation in heterogeneous microstructure and defect structure of FeMnNi MEA.

Dynamic behavior of CrMnFeCoNi high-entropy alloy in impact tension

High-entropy alloys (HEAs), recently emerging alloy materials with numerous excellent performances, may have a wide application prospect in impact engineering. However, previous research regarding the mechanical behavior of HEAs has primarily focused on quasi-static testing, whereas the dynamic mechanical behavior of HEAs at high strain rates remains elusive. In this paper, the unusual simultaneous strength-plasticity enhancement and the inhibition of the high strain rate embrittlement of CrMnFeCoNi HEA in impact tension were revealed via split Hopkinson tensile bar (SHTB) with high-speed photography. Quantitative microstructural analysis indicates that the cooperation of twins and dislocations is the crucial mechanism for the synchronous enhancement of strength-plasticity in this alloy under impact tension. A thermo-viscoplastic constitutive model based on dislocations and twins evolution was developed to describe dynamic mechanical behavior. The high plastic hardening under dynamic tension was revealed to be induced by high dislocation forest hardening and strong resistance of twins to dislocation motion. The excellent combination of dynamic strength-plasticity of CrMnFeCoNi HEA makes it becoming a promising candidate for impact engineering applications.

Image Processing using Open Source Tools and their Implementation in the Analysis of Complex Microstructures

AbstractConsidering the dependance of materials’ properties on the microstructure, it is imperative to carry out a thorough microstructural characterization and analysis to bolster its development. This article is aimed to inform the users about the implementation of FIJI, an open source image processing software for image segmentation and quantitative microstructural analysis.The rapid advancement of computer technology in the past years has made it possible to swiftly segment and analyze hundreds of micrographs reducing hours’ worth of analysis time to a mere matter of minutes. This has led to the availability of several commercial image processing software programs primarily aimed at relatively inexperienced users. Despite the advantages like ‘one-click solutions’ offered by commercial software, the high licensing cost limits its widespread use in the metallographic community.Open-source platforms on the other hand, are free and easily available although rudimentary knowledge of the user-interface is a pre-requisite. In particular, the software FIJI has distinguished itself as a versatile tool, since it provides suitable extensions from image processing to segmentation to quantitative stereology and is continuously developed by a large user community. This article aims to introduce the FIJI program by familiarizing the user with its graphical user-interface and providing a sequential methodology to carry out image segmentation and quantitative microstructural analysis.

Deformation mechanisms of granulite-facies mafic shear zones from hole U1473A, Atlantis Bank, Southwest Indian Ridge (IODP Expedition 360)

Lower-crustal shear zones from hole U1473A (IODP Expedition 360) were studied via quantitative microstructural analysis and thermodynamic modelling to constrain deformation conditions during detachment faulting. Porphyroclasts of clinopyroxene and orthopyroxene, plagioclase and olivine are included in a fine-grained, polyphase matrix that contains plagioclase-rich layers. Microfractures occur in orthopyroxene, and core-mantle structures are common in all porphyroclasts. Crystallographic fabrics in clinopyroxene clasts indicate activation of (010)[001] slip system, whereas the rimming neoblasts show activity of both (010)[001] and (001)[100]. Fabrics of plagioclase-rich layers suggest the activation of the (010)[100] slip system. Phase mixing and weak crystallographic fabrics in the polyphase matrix point to oriented-growth during diffusion-assisted grain boundary sliding. Thermodynamic modelling indicates that the gabbroic shear zones formed at ~900–920 °C and 2.2–2.7 kbar, under melt-present conditions, and re-equilibrated down to 835 °C during exhumation, as indicated by hornblende–plagioclase thermometry. Our results suggest that deformation in the lower parts of Atlantis Bank was accommodated by a combination of brittle fragmentation and viscous flow during in-situ melt-consumption back-reaction. Such mechanisms effectively resulted in strain localisation in fine-grained, polyphase shear zones that contributed to the weakening of the ocean crust during detachment faulting and subsequent exhumation of the Atlantis Bank core complex.

Microstructure Evolution and Thermal Stability of AZ31 Alloy Deformed by Multi-Pass DSR

Experiments were conducted to investigate the microstructural evolution of AZ31 alloy when deformed by multi-pass differential speed rolling (DSR) using the simplest modification of route A passing sequence. Microstructural observations were taken on all three planes of the sample to obtain a three-dimensional view. Based on quantitative microstructural analysis, the counts of the fine DRX grains increased with increasing number of DSR passes, while the fine DRX grains’ size was consistent in each pass. These results signified that the refinery process was attributed to dynamic recrystallization. Thermal stability was perceived by examining the evolution in microstructure and microhardness value of the 4-pass DSR sample during isochronal annealing over a range of temperature from 423 to 723 K. The increase in distortion energy with multi-pass DSR resulted in the decrease in critical temperature for the initiation of recrystallization upon annealing at 423 K, which induced an immediate drop in microhardness.

Qualitative and Quantitative Microstructural Analysis of Copper for Sintering Process Optimization in Additive Manufacturing Applications

Abstract This work will present possibilities for the characterization of copper powder green bodies and sintered copper microstructures during pressureless sintering. The introduction of new parameters to microstructural characterization based on qualitative and quantitative microstructural analysis will facilitate the systematic optimization of the sintering process. As a result of the specific evaluation of the microstructure evolution, conventional isothermal sintering could be successfully replaced by multi-step temperature profiles, thus achieving sintering densities of more than 99 % by simultaneously reducing process time. This systematic optimization of the sintering process of Cu through specific microstructural analysis may now be applied to sinter-based manufacturing technologies such as Binder Jetting and Metal Powder Injection Moulding, enabling the manufacture of complex and highly conductive Cu parts for applications in electronics.

Clay soil behaviour due to long-term contamination by liquid petroleum fuels: microstructure and geotechnical properties

The article presents the results of qualitative and quantitative microstructural analysis, and the basic properties of clay soils subjected to long-term contamination by liquid petroleum fuels (LPF). Comparative study of undisturbed, contaminated in situ clay soil (CS) and reference uncontaminated soil (US) was performed. Soil contamination by these compounds causes transformation of microstructure and changes of geotechnical parameters. Microstructure is a key factor in the interpretation of soil properties. Microstructural analyses were performed with application of scanning electron microscope (SEM) and STIMAN software. It was estimated that contaminated soil is characterised by lower moisture content, plasticity, pH and zeta potential, and by higher bulk density and consistency index. Due to hydrocarbon contamination, soil microstructure changed from highly anisotropic mixed laminar-turbulent into uniform matrix type. Comparative quantitative analysis of the microstructure indicated redistribution of the pore space expressed by changes in porosity, pore number and shape, decrease of microporosity, and increase of elongated mesopores number.

Slurry development for lithography-based additive manufacturing of cemented carbide components

This article describes slurry development for lithography-based additive manufacturing (AM) of cemented carbide components. Due to their superior material properties compared to steels, tungsten carbide‑cobalt hardmetals are an exciting material for manufacturing tools. AM technologies' geometric freedom makes it possible to design more efficient tools compared to other manufacturing techniques. These technologies are known as resource-efficient and sustainable processes. The material that is not required for manufacturing is re-used for the production of additional components. The high energy input in laser powder bed-based AM processes leads to strong grain growth and brittle phases, so the achievable mechanical properties are significantly limited. Lithography-based additive manufacturing shows high potential due to the manufacturing of a polymer-bound green body and a subsequent heat treatment. Tungsten carbide‑cobalt (88–12 wt%) slurries were developed with a solid content of 40 vol%, based on the resin's reactive components. Dispersants made it possible to increase the maximum processable volume fraction of solid particles. A thixotropic agent helped stabilize the slurry. Rheological investigations characterized these effects. The influence of the photoinitiator concentration and the volume fraction of tungsten carbide and cobalt particles on the curing depth was analyzed. Prepared slurries and manufactured multi-layered green bodies were evaluated for homogeneity using quantitative microstructure analysis.

New Approach to Distinguish Copper Molten Marks Based on Quantitative Microstructure Analysis Using Electron Backscatter Diffraction

Molten marks identified at a fire site can aid in determining the cause of a fire. Quantitative analysis of such molten marks has not yet been reported, despite several identification methods for molten marks being proposed based on optical micrographs. Herein, we propose a new methodology to establish the quantitative microstructure parameters of the molten marks using electron backscatter diffraction (EBSD). The globules were generated by heating the copper conductor to 1100°C in a non-energized state. Then, the arc beads were prepared by shorting the copper wire at 25°C and 900°C in an energized state. The globules did not show evident demarcation lines and indicated that the microstructure consisted of globular or dendritic grains; this demonstrated that their characteristics were distinctly different from those of arc beads. However, the primary arc beads (PABs) shorted at 25°C exhibited a strong (001) texture perpendicular to the demarcation line and comprised large fractions of columnar grains with a small grain aspect ratio (GAR). The microstructure of secondary arc beads (SABs) shorted at 900°C presented a mixture of elongated and equiaxed grains with a large GAR and no specific development of texture. The GAR and (001) fraction perpendicular to the demarcation line could be discriminant parameters of PABs and SABs. Consequently, EBSD methods can be newly applied for the classification of globules, PABs, and SABs based on the quantitative microstructure information and orientation distribution.