Backscattering X-ray Research Articles

Investigation on micro-mechanics properties of machined metamorphic layer based on crystal plasticity finite element method

Surface materials endure significant mechanical and thermal loads during machining, leading to microstructural changes and the formation of metamorphic layers. These layers exhibit altered crystallographic characteristics, such as grain size, misorientation angles, and dislocation density, resulting in mechanical properties that differ from the bulk material. This study examines the microstructural evolution of the metamorphic layer using electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). Based on microstructure characterization, a 3D reconstruction method was developed using a representative volume element (RVE). The crystal plasticity finite element method (CPFEM) was employed to establish the relationship between the microstructure and micromechanical properties, including microhardness, elastic modulus, and yield stress. The proposed method was validated by comparing simulation results with experimental data obtained from micro-pillar compression tests and nanoindentation tests. The results demonstrated a strong correlation in stress-strain curves, and the microhardness measurement error at indentation depths of 400 nm was less than 10 %.

Analysis of Stored Energy Distribution in Three Directions of Tantalum in Deformed and Annealed States

Microstructures in high-purity tantalum (Ta) were analyzed in three directions, focusing on the evolution of stored energy during rolling and heating processes. Results indicated significant fluctuation in the transaction direction (TD) surface, which was observed in both deformed and annealed states. This phenomenon is attributed to the alternately arranged {111}<uvw>(<111>//normal direction (ND)) and {100}<uvw>(<100>//ND) oriented grains, coupled with the substantial energy difference between them, even after 12 passes. Additionally, through the estimation and calculation of stored energy based on band contrast from electron backscatter diffraction and X-ray line profile analyses, the recovery kinetics for different directions and grain types were quantitatively assessed. Findings revealed that the dislocation density of {111} grains decreased significantly more than that of {100} grains when annealed at 1073 K. The degree of recovery was closely related to temperature, dislocation density, and dislocation type.

On the investigation of microstructure and mechanical properties of the AlCoCrFeNi2.1/316 L dissimilar spot-welded joint

This study receives a free-defect spot-welded joint, using the base metal of AlCoCrFeNi2.1/316 L, for the first time, by a resistance spot welding technique. Electron backscatter diffraction, X-ray diffraction, and scanning electron microscopy were used to analyze the microstructure of the nugget and heat-affected zone of the spot-welded joint. Mechanical experiments were conducted to gain mechanical properties such as micro-hardness and shear tensile strength. The nugget on the side of 316 L and AlCoCrFeNi2.1 is not fully symmetrical, and the nugget offset is observed on the AlCoCrFeNi2.1 side owing to dissimilar thermo-physical properties. Thermodynamic calculation and XRD diffraction analysis confirm that both austenite and (Fe, Ni) phases are existent in the nugget zone. Eventually, under a shear load, an interface fracture of the spot-welded joint was observed and the fracture morphology was examined. This work could serve as an initial basis for further research on high entropy alloy resistance spot welding.

Effect of cyclic loading on microstructure and plastic deformation in heat-treated Co–28Cr–6Mo alloy fabricated via laser powder bed fusion: An in situ synchrotron X-ray diffraction study

We present a systematic microstructure-oriented plasticity investigation of an additively manufactured cobalt-based alloy aiming to relate microstructural changes to the fatigue resistance. A load-controlled cyclic test in the low-cycle fatigue regime was utilized to study mechanical response and microstructural changes in the alloy after reverse phase transformation heat treatment. Deformation-induced FCC → HCP phase transformation was followed using in situ synchrotron X-ray diffraction combined with ex situ electron backscatter diffraction and scanning electron microscopy. Scanning transmission electron microscopy provided experimental evidence of the presence of precipitates in the solution annealed sample. It was found, that a stepwise increase in plastic deformation is attributed to nucleation and growth of different martensitic crystallographic variants. These insights into plasticity and microstructural changes suggest that the reverse phase transformation heat treatment is an effective approach for improving the fatigue resistance of low stacking fault energy alloys, that are susceptible to deformation-induced martensitic transformation.

Microstructure and crack propagation behavior of 2195 Al–Li alloy with different orientations in the friction stir welding nugget zone

The 2195 Al–Li alloy is widely used in the aerospace field, where using friction stir welding technology can achieve lightweight and reduced wear designs for components. Fatigue failure, as one of the main modes of damage affecting the life and reliability of structural components, is particularly significant. This paper thoroughly explores the differences in microstructure and fatigue crack propagation behavior between the advancing side and retreating side of the friction stir welded joint in different sampling directions, providing a theoretical basis for enhancing the fatigue performance of friction stir welds. Characterization of the microstructure of the samples was performed using Electron Backscatter Diffraction (EBSD) and X-Ray Diffraction (XRD), and the fatigue properties were investigated using fatigue crack propagation rate curves and crack growth rate curves. The results indicate that the longitudinal base material grains tend to a fibrous structure, while the axial base material grains are distributed in a lamellar fashion. Compared to the advancing side of weld nugget zone, the retreating side of weld nugget zone has significantly reduced grain size and texture types. The fatigue performance of the retreating side of the weld nugget zone is superior to that of the advancing side, and the circumferential welds outperform the longitudinal welds in terms of fatigue performance.

Effect of Mg on Plasticity and Microstructure of Al-Mg-Ga-Sn-In Soluble Aluminum Alloy.

Soluble aluminum alloy materials used in underground operational tools are synthesized via a high-temperature smelting process. The microstructure and composition distribution of the alloy were analyzed using X-ray diffraction, metallographic microscopy, and scanning electron microscopy with energy-dispersive X-ray and electron backscatter diffraction techniques. The mechanical properties were evaluated using a universal testing machine and hardness tester, while solubility assessments were conducted in a constant-temperature water bath. This study focuses on the plasticity and dissolution characteristics of Al-Mg-Ga-Sn-In alloys with varying Mg contents. The tensile strength (σb) of the alloy was 181.99 MPa, with an elongation (δ) of 27.49% and cross-sectional shrinkage (φ) of 11.67% at a magnesium content of 3.0 wt.%. Additionally, in the compressive test, the compressive yield strength (σsc) was recorded at 188.32 MPa, while the compression rate (δ) was 27.06% and the section expansion rate (φ) was 138.66%. Furthermore, the alloy demonstrated the ability to dissolve spontaneously in water at 90 °C, exhibiting an average dissolution rate of 1.0 g·h-1cm-2 and a maximum dissolution rate of 3.25 g·h-1cm-2 after 12.0 h. Consequently, this alloy composition not only satisfies the requirements for rapid solubility but also exhibits favorable plasticity, providing a novel reference for the selection of soluble aluminum alloy materials.

Application of Soft Magnetic Composite in XEV Motor Core Manufacturing: Process Effects and Performance Analysis

This study explores the application of AncorLam HR (Höganäs, Sweden), a soft magnetic composite material, in the stator core of an axial flux permanent magnet drive motor. Building on previous research that provided mechanical and thermal properties of the material, the focus is on analyzing how the manufacturing process affects the motor core’s shape. A bulk prototype was created based on case 3, which demonstrated the least deviation in density and internal stress. The prototypes were produced under the conditions of SPM 7 and 90 °C, and a heat treatment in a nitrogen atmosphere for 1 h, resulting in an average density error of 0.54%, confirming process effectiveness. A microstructural analysis using scanning electron microscopy (SEM) on Sample 2, with the highest density, confirmed consistency between simulation and prototype trends. Electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analyses revealed that the internal phase structure remained unchanged. Energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) identified the elimination of phosphorus (P) during molding, affecting the insulating layer, a critical factor for SMC materials. In motor simulations and actual measurements, the average torque was recorded as 37.7 N·m and 34.7 N·m at 1500 rpm and 27.7 N·m and 25.1 N·m at 2000 rpm, respectively. The torque comparison observed in the actual measurements compared to the simulation results indicates that the output loss increases in the actual measurements due to the deterioration of the insulation performance judged based on the microstructure evaluation. This study confirms the viability of using AncorLam HR in motor cores for electric vehicles and provides key data for improving the performance.

The evolution and toughening mechanism of austenite in high Co–Ni ultrahigh strength steel

The austenite, as a “soft” phase, has a significant impact on the mechanical properties in ultrahigh strength steel. The morphology, size, and distribution of austenite play a critical role in toughness of steel. This study concentrates on morphology, size, and distribution of austenite subjected to solid solution, cryogenic, and aging treatments and explores its evolution characterized by transmission electron microscopy, scanning electron microscopy, electron backscatter diffraction and x-ray diffraction. The toughening mechanism of austenite with different characterization was investigated through charpy impact testing and fracture morphology analysis. The results indicate that filmy and blocky austenite existed at the lath boundary of martensite. Blocky austenite and some filmy austenite were eliminated after cryogenic treatment, while approximately less than 15 nm filmy reverted austenite was formed after aging treatment. Filmy reverted austenite at the boundary of martensite laths can enhance toughness. Retained austenite without cryogenic treatment can induce the formation of larger blocky austenite, which decreased toughness.

Investigation of corrosion resistance offered by the Fe-based clad layer under salt spray and electrochemical workstations

The present work aims to evaluate the electrochemical characteristics of the Fe–based alloy coating formed on the 27SiMn steel substrate under neutral salt spray and 3.5 wt% NaCl environments. By adopting the high-speed laser cladding technique, the Fe-based clad layer was fabricated to perform microstructural and electrochemical characterizations. The microstructure and phase of the coating were analyzed using a scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), and its corrosion performance was also discussed using the salt spray corrosion chamber and the electrochemical workstation. The results show that the microstructure of the coating surface contains equiaxed crystals and long dendritic crystals which arise due to the higher solidification rate after the cladding process. The Fe–based coating was rich in FeCr phase throughout its microstructure without the formation of the intermetallic compounds. Compared to the substrate, the corroded surface of the coating tends to be compact containing a few corrosion pits after different corrosion times, which is attributed to the formation of Cr oxide on it. The electrochemical tests on the potentiodynamic polarization curve (PPC) and electrochemical impedance spectrum (EIS) indicate that the corrosion resistance of the coating is superior to the substrate, presenting a higher corrosion potential (−0.298 V), lower passive current density (1.36 × 10−6 A•cm2), and higher charge transfer resistance (8.23 × 106 Ω·cm2). Additionally, the corrosion mechanism of coating in salt spray and electrochemical tests is the local pitting corrosion due to the autocatalytic effect on the localized region, which facilitates Cl− ions penetrating the coating and leads to the dissolution of Fe and Cr oxides.

Increased bone mass but delayed mineralization: in vivo and in vitro study for zoledronate in bone regeneration

BackgroundBisphosphonates (BPs) are widely used to inhibit excessive osteoclast activity. However, the potential to compromise bone defect healing has limited their broader application. To better understand the influence of BPs on bone regeneration, we established a bone grafting model with Zoledronate administration, aiming to deepen the understanding of bone remodeling and mineralization processes.MethodsA bone grafting model was established in the distal femurs of male Sprague–Dawley rats. The experimental group received systemic administration of Zoledronate (ZOL, 0.2 mg/kg, administered twice). Histological analysis and immunohistochemistry (IHC) were employed to assess osteoblastic and macrophage activity, tartrate-resistant acid phosphatase (TRAP) staining was used to evaluate osteoclastogenesis. Mineralization was assessed through Micro-CT analysis, Raman spectroscopy, and back-scatter scanning electron microscopy (BSE-SEM). Additionally, the in vitro effects of ZOL on osteoblast and osteoclast activity were investigated to further elucidate its impact on bone regeneration.ResultsIn vivo, the ZOL group showed increased bone mass, as observed in histological and radiological assessments. However, Micro-CT, Raman spectroscopy, and BSE-SEM detection revealed lower mineralization levels in ZOL group's regenerated bone. Acid-etched SEM analysis showed abnormal osteocyte characteristics in ZOL-group’s regenerated bone. Simultaneously, elevated osteopontin (OPN), F4/80 expression along with reduced TRAP expressing was found in the grafting region of ZOL group. In vitro, ZOL did not negatively impact osteogenetic activity (ALP, BMP4, OCN expression) at the tested concentrations (0.02–0.5 g/ml) but significantly impaired mineralization and inhibited osteoclast formation, even at the lowest concentration.ConclusionsThis study highlights a less recognized negative effect of ZOL on bone mineralization during bone regeneration. More research is needed to elucidate the underlying mechanism.

Performances enhancing of supersulfated cement (SSC) using waste alkaline activators: Red mud and carbide slag

Supersulfated cement (SSC), since its invention, showed lower early-age strength gain, which has limited its practical applications. The urgent issue is how to regulate and enhance its early-age performance. In this context, solid waste materials such as bauxite residue-red mud (RM) and carbide slag residue (CS) from acetylene production by calcium carbide hydrolysis were used to improve the hydration and performance of SSC. By utilizing a range of analytical techniques such as isothermal calorimetry (IC), X-ray diffraction (XRD), backscatter scanning electron images (BSE), and thermogravimetric analysis (TGA), the hydration process, phase assemblages and microstructure of CS/RM-modified SSC were systematically investigated. It’s found that CS, as a calcareous alkaline activator, act as a regulator for adjusting the two main hydration reactions of C-A-S-H deposition and ettringite formation in SSC. The alkaline activator induces the hydration of slag and promotes the formation of hydration products. However, an excessively high dosage of carbide slag delays the primary ettringite formation reaction because it inhibits the dissolution of slag and promotes the formation of outer products. It leads to a looser and more porous paste matrix, resulting in higher expansion strain and poor strength gain at full curing ages. In contrast, red mud improves the hydration rate and enhances the hydration degree of SSC within the studied content (up to 30 wt%). With addition of red mud, SSC hydration is significantly advanced and deepened, resulting in more hydrates, particularly inner products. Red mud facilitates the depolymerization of the slag glass network and promotes the forming of nuclei and growth of hydration products. However, an excessively high red mud content would lead to a looser and more porous paste matrix due to the characteristics of red mud particle itself. An optimal red mud content has been identified as 20 wt%.

Increased cancellous bone mass accompanies decreased cortical bone mineral density and higher axial deformation in femurs of leptin-deficient obese mice

IntroductionLeptin is a pleiotropic hormone that regulates food intake and energy homeostasis with enigmatic effects on bone development. It is unclear if leptin promotes or inhibits bone growth. The aim of this study was to characterize the micro-architecture and mechanical competence of femur bones of leptin-deficient mice. Materials and methodsRight femur bones of 15-week old C57BL/6 (n = 9) and leptin-deficient (ob/ob, n = 9) mice were analyzed. Whole bones were scanned using micro-CT and morphometric parameters of the cortex and trabeculae were assessed. Elastic moduli were determined from microindentations in midshaft cross-sections. Mineral densities were determined using quantitative backscatter scanning electron microscopy. 3D models of the distal femur metaphysis, cleared from trabecular bone, were meshed and used for finite element simulations of axial loading to identify straining differences between ob/ob and C57BL/6 controls. ResultsCompared with C57BL/6 controls, ob/ob mice had significantly shorter bones. ob/ob mice showed significantly increased cancellous bone volume and trabecular thickness. qBEI quantified a ∼7% lower mineral density in ob/ob mice in the distal femur metaphysis. Indentation demonstrated a significantly reduced Young's modulus of 12.14 [9.67, 16.56 IQR] GPa for ob/ob mice compared to 23.12 [20.70, 26.57 IQR] GPa in C57BL/6 mice. FEA revealed greater deformation of cortical bone in ob/ob as compared to C57BL/6 mice. ConclusionLeptin deficient ob/ob mice have a softer cortical bone in the distal femur metaphysis but an excessive amount of cancellous bone, possibly as a response to increased deformation of the bones during axial loading. Both FEA and direct X-ray and electron microscopy imaging suggest that the morphology and micro-architecture of ob/ob mice have inferior biomechanical properties suggestive of a reduced mechanical competence.

Mechanistic role of vanadium microalloying in improving corrosion resistance of low carbon bainitic steel

We here investigated the effect of vanadium microalloying on the microstructure, mechanical properties, especially corrosion performances of low carbon bainitic steels. The corrosion behaviors of the steels with different vanadium contents in 3.5 wt% NaCl solution were evaluated by electrochemical tests (including polarization curves and electrochemical impedance spectroscopic measurements) and alternating immersion test (including weight loss and rust layer observation). Results show that the mechanical properties and corrosion resistance of low carbon bainitic steels can be synergistically improved with vanadium microalloying. With help of the electron backscatter diffraction characterization and scanning Kelvin probe force microscopy, we first discovered that although the number of micro-galvanic couples increases because of grain refinement, the Volta potential gradient between the matrix and grain boundaries are decreased with vanadium microalloying, which can promote the formation of compact protective rust layers and improve the corrosion resistance of vanadium micro-alloyed low carbon bainitic steels.

Microstructures and wear properties of CoCrFexNi (x = 0, 1) medium-entropy alloy coatings prepared by laser cladding

PurposeHigh-nitrogen steel is a common material for the manufacture of drilling equipment such as drill collars. However, its poor surface properties often limit its applications. The purpose of this paper is to find a way to enhance the surface performance of high-nitrogen steel, which is expected to improve the wear resistance of high-nitrogen steel.Design/methodology/approachThe CoCrNi and CoCrFeNi medium-entropy alloy (MEA) coatings were prepared on high-nitrogen steel substrate by laser cladding technology. The microstructure, phase composition and element distribution of the fabricated coatings were investigated using scanning electronic microscopy, electron backscatter diffraction and X-ray diffraction. The phase structure, phase stability and structural stability of the CoCrNi and CoCrFeNi MEAs were investigated in combination with phase diagram calculation and molecular dynamics. Then the wear tests were carried out for coatings.FindingsThe results show that both prepared MEA coatings have good quality and contain a single face-centered cubic phase. The wear performance of MEA coatings is improved by the refinement of grain size and the increase of dislocation density. Due to the addition of Fe atoms, the lattice distortion of the CoCrFeNi system increased, resulting in a higher dislocation density of the coating. Cr atoms in the CoCrFeNi system are the largest, and the local lattice distortions induced by them are greater. Through this study, MEA coatings with high hardness can be expanded to drilling field applications.Originality/valueCoCrFeNi and CoCrNi MEA coatings were successfully prepared on the surface of high-nitrogen steel for the first time without obvious defects. The micromorphology and grain orientation of the different kinds of coatings were discussed in detail. The hardness-strengthening mechanism and structure stability of the coatings were illustrated by experiments and molecular dynamics simulations.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0116/

Interfacial bond behavior of steel fibers embedded in manufactured sand-based ultra-high performance concrete

The interfacial bond region between matrix and fibers is a non-negligible weak link that can significantly affect the mechanical properties of manufactured sand-based ultra-high-performance concrete (UHPMC). This study investigates the interfacial bond characteristics between steel fiber-UHPMC matrix using single-fiber pullout tests. Four variable parameters were considered: manufactured sand (MS) replacement ratio, stone powder content, fiber embedment length, and steel fiber geometry. Additionally, the microstructure of the steel fiber-UHPMC matrix interface was evaluated using backscattered electron microscopy (BSEM) and scanning electron microscopy (SEM). The results indicate that two typical failure modes including fiber pullout slip failure (in straight and hooked-end fibers) and fiber rupture failure (in corrugated fibers) were observed. The analysis of interfacial evaluation indicators shows that increasing the MS replacement ratio from 25 % to 100 % results in a decreasing trend in peak load, peak tensile stress, and energy consumption. Peak bond strength decreases with increasing embedment length. With the increase in stone powder content, the peak load, peak bond stress, and energy consumption increase initially and then decrease. Additionally, the interfacial failure mechanisms between straight/hooked-end steel fibers and the UHPMC matrix were further elucidated through bond-slip behavior characterization and microstructure analysis. Finally, a design-oriented bond-slip model was developed to predict the interfacial pull-out behavior of steel fiber -UHPMC matrix, showing favorable agreement between predicted and test results. These findings contribute to understanding the interfacial pullout behavior of steel fibers-UHPMC matrix, providing data reference for the performance optimization of UHPMC.

Decoding ceramic fracture: Atomic defects studies in multiscale simulations

Microstructural atomic defects, including voids, cleavage, and inclusions, are commonly observed in alumina materials, and their impact on mechanical properties, such as fracture stress and toughness, is significant. In this paper, we introduce novel alumina models that incorporate experimentally observed void features. An atomic model is established to study the effects of micro-structural void features on fracture properties and atomic structure changes using molecular dynamics simulations. The electron backscatter diffraction and scanning electronic microscopy analysis of experimental samples are used to evaluate microstructural features that are used as inputs to the simulations (e.g., void aspect ratio, void angle). We apply an innovative Atomistic-to-Continuum (ATC) method based on Riemann sums to bridge atomic and continuum mechanics theories, evaluating the resistance of materials with atomic defects to crack propagation. The results show the greatest effects of pore angles on weakening mechanical properties such as peak strength and fracture energy density. The accuracy and efficiency of the ATC method in evaluating stress intensity factors are used to calculate the mechanical responses. Additionally, we establish a multiple layer perceptron neural network to evaluate the complex relationship between void features (aspect ratio, pore angle, relative distance) and typical fracture properties (fracture stress, critical stress intensity factor). A meta-analysis of these results from both machine learning methods and molecular dynamics simulations reveals the significant impact of each void feature on the sensitivity of typical fracture properties (peak strength, critical stress intensity factor at peak strength) and highlights the critical role of aspect ratio on fracture properties.

Fragmentation /spheroidization of constituent phases and correlated flow softening during thermomechanical processing of AlCoCrFeNi2.1 eutectic high entropy alloy

The present study explores the morphological evolutions of constituent phases during the hot deformation process of a promising as-cast AlCoCrFeNi2.1 eutectic high-entropy alloy. Through which, a quasi-in-situ approach was employed using the Poliak-Jonas technique to carefully select interruption strains for conducting hot compression tests at 1000 °C. This approach allowed for tracking the sequence of microstructural evolutions. Furthermore, to understand the dominancy of shearing or thermally activated fragmentation mechanisms responsible for these evolutions, hot compression tests were conducted at different strain rates. Encountering an unexpected sharp softening behavior in the hot compression flow curve, its underlying micro-mechanisms were investigated using electron backscatter diffraction (EBSD) characterization and scanning electron microscopy (SEM) micrographs combined with detailed image processing and numerical calculations. It is shown that lamellar B2 eutectic regions underwent significant spheroidization with an increase in strain rate (from 12.6% ± 3.3%–64.5% ± 9%), while dendrites fragmentation was more pronounced in lower strain rates. These findings indicate that dynamic spheroidization and dendritic fragmentation mechanisms predominantly contribute to the aforementioned softening behavior observed in the alloy at high temperature.

Examining fish scale biomineral from Atlantic salmon populations.

Fish scale microchemistry can be used to make life-history inferences, although ecological studies examining scale composition are relatively rare. Salmon scales have an external layer of calcium phosphate hydroxyl apatite (HAP). The structure, hardness, and calcium content of this layer have been shown to vary within and between species. This variation may lead to misinterpretation of trace element profiles. This study uses backscatter scanning electron microscopy with electron dispersive spectrometry to compare scales from salmon populations and to present a more detailed analysis of scale HAP than was previously available. Our findings extend the range of salmon populations for which HAP Ca is available and confirm previous findings that the HAP Ca is relatively invariable within this species.

Low temperature tensile behavior and microstructure analysis of copper containing antibacterial stainless steel

Using Shimadzu AGS-100KN universal tensile testing machine, tensile tests were conducted on copper containing antibacterial stainless steel at 25 °C, −20 °C, −60 °C, −100 °C, and −140 °C. The fracture morphology and microstructure evolution of the material were then analyzed using various techniques including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The experimental findings showed that with the decrease of deformation temperature, the ultimate tensile strength(UTS) increased by about 49.7 %, the yield strength (YS) increased by about 35.5 %, and the elongation(EI) decreased by about 27.3 %, showed obvious low temperature strengthening effect. The High-angle grain boundaries (HAGBs) increased with decreasing temperature, while low-angle grain boundaries (LAGBs) decreased. The plasticity gradually decreased and the strength gradually increased, resulting in an increase in its ability to resist deformation. The number of precipitated phases gradually increased, and the size also gradually becomes larger, and the interaction between the diffusely distributed precipitated phases and dislocations led to precipitation strengthening. With the decrease of temperature, the stacking fault energy gradually decreased, the SFE was 21.26 mJ/m2 at the temperature of −140 °C. The main plastic deformation mechanism of copper-containing austenitic stainless steel in the low-temperature tensile process was transformed from deformation twins to strain-induced martensitic phase transformation.

Potential of diagnostic electron microscopy of calcification, pathological neovascularization and elastolysis in combination with phenotyping of cell populations in large arteries

Aim. To determine the potential of diagnostic electron microscopy of intraplaque processes (severity of lipid damage, fibrous cap thickness and condition, severity of pathological neovascularization, presence, nature and severity of calcification, ratio and distribution of various cell populations).Material and methods. The study objects were plaques removed during endar­terectomy from the human carotid artery and segments of the human internal mammary artery removed during coronary bypass surgery. Whole specimens were subjected to chemical fixation, staining with heavy metal salts, embedding in epoxy resin followed by layer-by-layer grinding, polishing, contrasting, visualization using back-scattered electron scanning electron microscopy and three-dimensional reconstruction with color mapping (modified EM-BSEM).Results. The use of a modified EM-BSEM made it possible to: 1) visualize the fibrous cap thickness and assess the extracellular matrix; 2) analyze the neointimal lipid distribution; 3) perform three-dimensional reconstruction and analyze the microenvironment of calcifications of various sizes; 4) visualize endothelial cells, defects in interendothelial contacts and the basement membrane of neointimal capillaries with their subsequent three-dimensional reconstruction; 5) perform an analysis of age-dependent defects in the basement membrane and internal elastic membrane of the internal mammary artery. The resolution of the obtained images was significantly superior to intravascular imaging methods (intravascular ultrasound and optical coherence tomography), allowing additional assessment of capillary fluidity, the degree of calcification encapsulation and the condition of elastic fibers. Three-dimensional reconstruction of calcifications, neointimal capillaries and elastic fibers made it possible to assess their spatial density and heterogeneity. Simultaneously with the identification and assessment of these histological structures, objective phenotyping of cell populations was performed, which made it possible to isolate macrophages and foam cells, vascular smooth muscle cells, fibroblasts and endothelial cells in atherosclerotic plaques and automatically identify them through color mapping determined by their electronic contrast distribution signatures.Conclusion. The modified EM-BSEM method allows for universal electron microscopic diagnosis of atherosclerotic and elastolytic lesions of large arteries with high information content about vascular remodeling and high accuracy. Electronic contrast distribution signatures unique for each cell population indicate the possibility of their automated phenotyping using specialized neural network algorithms.