Morphology Of Inclusions Research Articles

Experimental Determination of a Strain State in a Bulk Forming of a Low Carbon Steel

An experimental metallographic method for determining strain distribution in a cold formed workpiece is presented in this paper. The method, based on the dependence of recrystallized grain size on prior deformation, was applied to a bulk formed element made of low carbon steel. Strain distribution was obtained by the calibration curve which gives the relation between recrystallized grain size and prior deformation. To determine strain values, the average grain size was measured in the longitudinal cross-section of the formed element. To accurately differentiate deformation zones, additional observation of carbides and nonmetallic inclusions morphology was utilized, also. The grain size and strain noticeably differ through the cross-section. It is observed that in the middle part, material flows freely through the die opening without significant deformation. From this zone, strain increases gradually, reaching the highest value at the contact surface of the die slope, while the top part flows radially having intermediate values of strain.

Effects of Cerium Content on the Nonmetallic Inclusions and Impact Toughness of Transformation‐Induced Plasticity Steel

The effects of Ce treatment on the inclusion evolution and impact toughness of as‐cast transformation‐induced plasticity (TRIP) steel are systematically investigated by scanning electron microscope (SEM) and impact toughness testing. The results reveal that in Fe‐2Mn‐1.5Al‐1Si‐0.2C steel without Ce, the primary inclusions consist of AlN, MnS, and Al2O3. After Ce addition, the inclusions evolve into Ce‐Al‐O, Ce2O2S, CeS, and Ce2O3 inclusions. The evolution of inclusions exhibits an initial reduction in both quantity and size with increasing Ce content, followed by a subsequent increase. In cases of excessive Ce content, there is an observable rise in the overall inclusion count, marked by the emergence of CeAs, CeP, and CeC2 inclusions. The segregation model suggests that P‐containing inclusions predominantly precipitate in the late solidification process, while As‐ and C‐containing inclusions form during the solid phase. When the Ce content reaches 0.0075 wt%, the minimum values of the number density and average diameter are 96.7 mm−2 and 1.6 μm, respectively. Furthermore, the influence of the size, morphology, quantity, and type of inclusions on the impact toughness are analyzed. The highest recorded impact energy is 6.8 J with a Ce content of 0.0075 wt%.

Sulfide Inclusions in an Al‐Killed Nonoriented Electrical Steel with Lanthanum Addition

Herein, laboratory experiments are conducted to evaluate the effect of sulfur and lanthanum content in the steel on the modification of inclusions. The amount, composition, morphology, and size of nonmetallic inclusions in the steel are observed using an automatic scanning electron microscope. Results show that as the lanthanum content in the steel increased from 0 to 72 ppm, the inclusions in the steel with 12 ppm sulfur are modified in the following order: Al2O3–CaO–MgO → LaAlO3 → LaAlO3–La2O2S → La2O2S. Similarly, when the sulfur content is 27 ppm, inclusions transformed in the order of Al2O3–CaO–MgO → LaAlO3 → LaAlO3–La2O2S → La2O2S → La2O2S–LaxS → LaxS as the lanthanum content increases from 0 to 150 ppm. Thermodynamic analysis using FactSage based on a private database is employed to reveal the mechanism for the modification of inclusions. Additionally, a kinetic model is established to study the transformation rate of inclusions in the steel after the addition of lanthanum and sulfur. Liquid Al2O3–CaO–MgO inclusions disappear after 800 s when the steel contains 12 ppm sulfur and 12 ppm lanthanum. The composition of inclusions is 53%LaAlO3–47%La2O2S at 1800 s, while it is 100%La2O2S and 80%La2O2S–18%LaxS–2%CaS when the lanthanum content is 33 and 72 ppm, respectively.

AI assisted steel cleanness evaluation: Predicting the morphology of La-traced non-metallic inclusions using backscattered-electron images

This study shows how computer vision, a field of artificial intelligence (AI), can be used to gain access to morphological information for a better process understanding and furthermore, how it can be implemented in the evaluation of active tracing experiments. Non-metallic inclusions (NMIs) play a crucial role in determining the chemical and physical properties of the final steel product. The active tracing technique allows for tracking the formation and modification mechanisms of detrimental NMIs throughout the steelmaking process by adding rare earth elements (REEs) to the melt. The interaction of REEs with NMIs results in the formation of traced multiphase particles and, therefore, lead to challenges for accurate evaluation by automated scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). However, obtaining information about the REE distribution in traced NMIs without extensive, time-consuming human effort is not feasible using the existing method. A two-step classification process with AI was established, which included training and testing of two random forest classifiers (RFC). The first RFC achieved for the binary NMI/non-NMI classification an accuracy of 94.8 %. Four different morphology-based classes were considered in the second classification, whereas traced homogeneous NMIs and NMIs with a high La content got classified with a precision exceeding 90 %. However, caution is required in interpreting results for traced heterogeneous NMIs, as they have a higher prediction error of 37.2 %.

Investigation on the formation mechanism of composite inclusions by multi-scale characterization in high manganese steel with yttrium addition

The rare earth modification of inclusions is an effective method to solve the critical issue of brittle inclusions leading to the failure of high manganese steel railway frog as one of the most essential assemble units of the railway operating system. The high manganese steel with rare earth yttrium was produced using a vacuum induction furnace. The multi-dimensional structural analysis of composite inclusions in the high manganese steel was performed to clarify the composition, crystal structure, and interface structure of the composite inclusions at multi-scales ranging from micrometers and nanometers to atoms and electrons. The chemical composition and morphology of composite inclusions were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy. After modification with rare earth yttrium, the MnS-Al2O3 composite inclusions in the steel transform into Y2S3-Y2O2S composite inclusions with smaller dimensions and approximately spherical shapes. The interface structure and crystallographic orientation of the Y2S3-Y2O2S composite inclusions were revealed as Y2O2S (100) // Y2S3 (5 0 3) by the focused ion beams scanning electron microscopy and the high-resolution transmission electron microscopy analysis. Moreover, the first-principles calculations were performed to obtain the adsorption energies and electronic structures of Y and S atoms at various positions on different terminations of the three low-index surfaces ((1 0 0), (110), and (111)) of Y2O2S, which reveals the adsorption pathway of Y and S atoms and formation mechanism of enclosed phase Y2S3 on the core phase Y2O2S that the adsorbate Y and S atoms grew parallel to the Y2O2S (1 0 0) surface and formed specific hexagonal ring structures of Y2S3 crystal.

Control of the Composition and Morphology of Non-Metallic Inclusions in Superduplex Stainless Steel

Duplex stainless steel is a unique material for cast products, the use of which is possible in various fields. With the same chemical composition, melting, casting and heat treatment technology, pitting and crevice corrosion were observed at the interphase boundaries of non-metallic inclusions and the steel matrix. To increase the cleanliness of steel, it is necessary to carefully select the technology for deoxidizing with titanium or aluminum, as the most common deoxidizers, and the technology for modifying with rare earth metals. In this work, a comprehensive analysis of the thermodynamic data in the literature on the behavior of oxides and sulfides in this highly alloyed system under consideration was performed. Based on this analysis, a thermodynamic model was developed to describe their behavior in liquid and solidified duplex stainless steels. The critical concentrations at which the existence of certain phases is possible during the deoxidation of DSS with titanium, aluminum and modification by rare earth metals, including the simultaneous contribution of lanthanum and cerium, was determined. Experimental ingots were produced, the cleanliness of experimental steels was assessed, and the key metric parameters of non-metallic inclusions were described. In steels deoxidized using titanium, clusters of inclusions with a diameter of 84 microns with a volume fraction of 0.066% were formed, the volume fraction of which was decreased to 0.01% with the subsequent addition of aluminum. The clusters completely disappeared when REMs were added. The reason for this behavior of inclusions was interpreted using thermodynamic modeling and explained by the difference in temperature at which specific types of NMIs begin to form. A comparison of experimental and calculated results showed that the proposed model adequately describes the process of formation of non-metallic inclusions in the steel under consideration and can be used for the development of industrial technology.

α-Synuclein aggregates amplified from patient-derived Lewy bodies recapitulate Lewy body diseases in mice

Extraction of α-Synuclein (αSyn) aggregates from Lewy body disease (LBD) brains has been widely described yet templated fibrillization of LB-αSyn often fails to propagate its structural and functional properties. We recently demonstrated that aggregates amplified from LB-αSyn (ampLB) show distinct biological activities in vitro compared to human αSyn preformed fibrils (hPFF) formed de novo. Here we compare the in vivo biological activities of hPFF and ampLB regarding seeding activity, latency in inducing pathology, distribution of pathology, inclusion morphology, and cell-type preference. Injection of ampLB into mice expressing only human αSyn (male Thy1:SNCA/Snca–/– mice) induced pathologies similar to those of LBD subjects that were distinct from those induced by hPFF-injection or developing spontaneously with aging. Importantly, αSyn aggregates in ampLB-injected Thy1:SNCA/Snca–/– mice maintained the unique biological and conformational features of original LB-αSyn. These results indicate that ampLB-injection, rather than conventional PFF-injection or αSyn overexpression, faithfully models key aspects of LBD.

Influence of MnS inclusion characteristics on generation of white etching cracks in 100Cr6 bearing steel

Wind turbine gearbox (WTGB) bearings suffer from premature failures through white etching cracks (WECs). To investigate causes of this failure mechanism, we tested two types of 100Cr6 bearing steel components. We carried out rolling contact fatigue experiments on standard washers and material extracted from a WTGB bearing. These differed strongly in morphology and orientation of non-metallic inclusions (NMIs) with respect to the raceway, especially of MnS-type. While the standard washer did not exhibit WECs formation, the WTGB bearing did - even under moderate conditions (1.9 GPa Hertzian pressure, 107 cycles). We therefore conclude that MnS-inclusions are a key factor in initiation of WECs in WTGB bearings.

Automated feature analysis as a tool for non-metallic inclusion analysis in solidified metals

In-depth analysis of the non-metallic inclusion population in solidified metals is essential considering the high cleanliness requirements for metallic components. For this purpose, automated feature analysis (AFA) is a powerful inclusion analysis tool, providing statistical supported information about quantity, elemental composition, morphology and size of inclusions. However, thorough data evaluation is imperative to ensure accurate and reliable results. The paper introduces the key principles of evaluating AFA data, emphasizing its capabilities and constraints by utilizing four large datasets obtained from solidified steel blocks, each containing a minimum of 4000 features. Additionally, methodologies for identifying characteristic inclusion species within a dataset, constructing suitable rulefiles for inclusion classification through statistical analyzes, and interpreting the resulting outcomes are presented. The size distribution of inclusions is analyzed using population density functions, focusing on the absolute inclusion count within specific size ranges. Cluster analysis is presented considering the inclusions‘ positional parameters.

Designing FeCr0.7NiCu0.5Ti0.5 high-entropy alloy doped with rare earth yttrium: Effects on microstructure and passive film

After constant potential passivation (CPP), the effect of rare earth yttrium (Y) on the corrosion resistance of the passive film on the surface of FeCr0.7NiCu0.5Ti0.5 alloy in H2SO4 was investigated. The results manifested that when Y content exceeded 0.04, the microstructure of Ni3Ti transformed into Cu5Y phase, and gradually expanded with the addition of Y. XPS etching analysis of passive film composition with changing etching depth and cyclic polarization analysis of passive film pitting corrosion sensitivity are two methods used to assess the corrosion resistance of alloy. Compared with FeCr0.7NiCu0.5Ti0.5 alloy and FeCr0.7NiCu0.5Ti0.5Y0.06 alloy, the passivation current density after CPP reduced from 5.682 × 10−3 to 4.630 × 10−4 A/cm2. With the addition of Y, the protection and density of the passive film was enhanced, resulting in an improvement in the corrosion resistance of the alloy. The pitting corrosion behavior was related to the changes in inclusion content and morphology caused by Y, and rare earth was advantageous to boost the passivation capability of FeCr0.7NiCu0.5Ti0.5 series alloy.

Effect of electromagnetic stirring on the transient flow, solidification and inclusion movements in the continuous casting slab mold

PurposeThe purpose of this study is to explore how a time-varying electromagnetic stirring (EMS) affects the fluid flow and solidification behavior in a slab caster continuous casting mold. Further, the study of inclusion movements in the mold is carried out under the effect of a time-varying electromagnetic field.Design/methodology/approachA three-dimensional coupled numerical model of solidification and magnetohydrodynamics has been developed for slab caster mold to investigate the inclusions transport by discrete phase model with the use of user-defined functions. Enthalpy porosity and the Lagrangian approach are applied to analyze the behavior of solidification and inclusion.FindingsThe study shows that the magnetic field density distribution has a radial symmetry in relation to the stirrer’s center. As the EMS current intensity increases, the strength of the lower recirculation zone gradually decreases and nearly disappears at higher intensities. Additionally, the area of localized remelting zone expands in the solidification front with rising current intensity. The morphology of inclusions and EMS current intensity have a significant impact on the behavior and movement of inclusions within the molten steel.Practical implicationsBy using the model, one can optimize the EMS parameter to enhance the quality of steel casting through the elimination of impurities and by improving the microstructure of cast that mainly depend on solidification and flow patterns of molten steel.Originality/valueUntil now, the use of time-varying EMS in the slab caster mold to study solidification and inclusion behavior has not been explored.

Gemological and Chemical Composition Characteristics of Basalt-Related Rubies from Chanthaburi-Trat, Thailand

The geographic origin determination of ruby is increasingly important in the gem trade and geological research. Unlike metamorphic-related ruby, the rarer basalt-related ruby has gained significant attention, especially from Thailand, a major producer of such gems. Thai rubies are classified as magmatic-related origin rubies, which can be found as xenocrysts (xenoliths) hosted by alkali basalts. This paper focuses on the gemological characteristics, inclusion morphology, identification, and geochemistry of basalt-hosted ruby from the Chanthaburi-Trat area in Thailand. Various instruments, including gemological conventional ones, Raman Spectrometer, EPMA, and LA-ICP-MS were used for the analysis. This study aimed to identify the distinctive characteristics of rubies from Thailand and find feasible methods for their geographic origin determination, in comparison with rubies from Cambodia, Myanmar, and Mozambique. Thailand samples exhibit diverse inclusion scenes and contain a variety of crystal or mineral inclusions. Raman spectroscopy results indicate the presence of anorthite, titanium oxide, and gypsum inclusions. The main chemical composition of the ruby consists of Al2O3, with trace elements including Fe, Cr, Si, Mg, Ti, Ga, V, Ca, and Ni. The color of Thailand ruby is correlated with the content of Cr and Fe. Chemical diagrams illustrating the contents of Fe, Mg, Cr, V, Ti, and Ga offer reasonable discrimination tools for differentiating rubies from various deposit types. The chemical compositions and inclusion characteristics of rubies from Thailand serve as reliable indicators for their origin identification. This study is an advantageous supplement to the research on Thailand rubies.

Effects of Na2O, K2O and B2O3 on Deformability of SiO2-MnO-Al2O3 Inclusion in High-Carbon Steel

Cord steel is used for making tire frames and wire saws for cutting silicon wafers. The diameter of mainstream cutting wire has been developed to be lower than 100 μm. The size and deformation ability of inclusions are very important to the wire breaking rate of cord steel during the drawing process. In order to improve the deformation ability of the inclusions in cord steel, alkali metal oxide was added into the molten steel to improve the inclusions in the steel so as to obtain good, plastic, low-melting-point inclusions. Mass fractions of 0.3%, 0.5% and 1.0% K2CO3, Na2CO3 and B2O3 were added into cord steel, which were melted in 10 furnaces (including 0% alkali metal oxides, mass fractions of 0.3%/0.5%/1.0% K2CO3, Na2CO3 and B2O3). The morphology and composition of inclusions were observed by SEM-EDS. Factsage phase diagram calculations and experimental results show that, with the increase in Na2CO3 content in cord steel, the aluminum content in the inclusions gradually decreased. When the mass fraction of Na2CO3 was 0.5% per ton, most of the inclusions in the steel fell in the low melting point region (less than 1300 °C). With the increase in K2CO3 content in cord steel, the silicon content in the inclusions decreased gradually. When the mass fraction of K2CO3 was 0.5% per ton, most of the inclusions in the steel fell in the low melting point region. The deformation ability of the inclusions added with 0.5% Na2CO3 in the steel during forging was better than that of the inclusions added with 0.5% K2CO3. After adding B2O3, the inclusions in the steel were SiO2-MnO-Al2O3 inclusions or inclusions with SiO2-MnO-Al2O3 as the core and BN wrapped around. Boron could not be dissolved into the inclusions for plastic modification.

Features and Restrictions of Electroslag Remelting with Silica‐Bearing Slags for Lightweight High Manganese Steel

Experiments are conducted to investigate the electroslag remelting process of Fe‐(20‐30)Mn‐(10‐12.0)Al‐(1‐2)C (wt%) steel in a short collar mold using a characteristic silica‐bearing slag to improve nonmetallic inclusion morphology. The effect of the “one‐slag melt” with silica on the changes in the chemical composition of the ESR ingot along its height is studied. The observed silicon pick‐up in metal at ESR is caused by the interaction of silica‐bearing slag with aluminum from metal composition (10%), stipulated by the ESR process nature and cannot be avoided. CALPHAD prediction of phase formation at observed changes of metal chemistry is proved by microstructure and EDS investigations of as‐cast metal of remelted ingot. Silicon pick‐up in obtained limits does not change the morphology of the main phases in the remelted Fe–Mn–Al–Cr‐C‐(Si) steel, but the microhardness of the phases becomes higher. Due to the low speed of remelting provided by ESR TC, the as‐cast metal structure and nonmetallic inclusions are refined. Experiments show that high silica‐bearing slag is not convenient for remelting high aluminum steels because of silicon transfer into ESR ingot at slag's silica reduction by aluminum.

Effect of La Content on Inclusion Morphology in Automobile Sulfur‐Containing Gear Steel SCr420H

The inclusion morphology of sulfur‐containing gear steel with different La addition (0, 0.08, 0.5, and 1%) is investigated in laboratory experiments. The La and S concentrations in steel melt significantly decrease with the holding time after La addition increases, leading to different types of inclusions with specific shapes. Inclusion transformation routes with the holding time increased under different La addition are summarized as follows: 1) 0%La addition: cluster‐like Al2O3 + cluster‐like MnS → irregular block‐like MgAl2O4 + cluster‐like MnS; 2) 0.08%La addition: cluster‐like LaAlO3 + spherical‐like La‐Al‐O‐S‐(MnS) → spherical‐like La‐Al‐O‐S‐(MnS) + spherical‐like La‐Al‐O‐S‐(MgO)‐(MnS) + cluster‐like MnS; 3) 0.5%La addition: flower‐like La‐O + spherical‐like La‐O‐S → spherical‐like La‐O‐S; and 4) 1%La addition: flower‐like La‐O + spherical‐like La‐O‐S → spherical‐like La‐O‐S + cubic‐like La‐O‐S‐N‐As. The results of hot compression suggest that La‐containing inclusions are less prone to the shape change than MnS; moreover, microcracks are formed at the surface of La‐containing inclusions. The nanoindentation test demonstrates that the hardness of La‐O‐S is higher than MnS. The high La addition has a remarkable effect on refractory degradation. For 0.5% and 1% La, dissolved La reacts with the MgAl2O4 phase in the MgO‐MgAl2O4 dual‐phase refractory and changes into LaAlO3.

High-temperature behaviour and interfacial damage of CGI: 3D numerical modelling

Superior mechanical and thermal properties, high wear resistance and a competitive price of compacted graphite iron (CGI) have made it an integral part of industry worldwide. In its applications in automotive engines, high-temperature environments cause thermal expansion that can result in emergence of interfacial damage in CGI. Although graphite-matrix interfacial damage is considered the main damage mechanism that can lead to total fracture of CGI, extensive research on CGI has not yet fully investigated this phenomenon at the microscale, especially under pure thermal loading. This paper focuses on the high-temperature performance of CGI and the onset of damage in graphite in thermal cycles. Three-dimensional numerical models are developed, with a single graphite inclusion embedded in a unit cell of the metallic matrix. Elastoplastic behaviour is considered for both phases in simulations. The effects of morphology and orientation of graphite inclusions on a response of an entire unit cell to thermal loading are investigated. Also, the influence of periodic and fully-fixed boundary conditions on the damage behaviour of CGI is discussed. The results can give a better understanding of the fracture mechanisms of CGI exposed to elevated temperatures.

Formation and Modification of Al2O3 and MnS Inclusions in Al-Killed Gear Steels via Ca Treatment

A laboratory study was carried out to better understand the factors that contribute to the formation of complex inclusions, as inclusions play an important role during steel production; if not properly managed, inclusions can cause nozzle clogging during continuous casting and also damage the steel’s mechanical properties and machineability. To determine the chemical composition of inclusions that are less detrimental to the machineability of Al-deoxidized and Ca-treated gear steels, thermodynamic calculations and automated scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), as well as electron probe micro-X-ray analysis (EPMA) with the wavelength dispersive spectroscopy (WDS) technique, were utilized. The findings demonstrated that the morphology of inclusions changed from irregular to a more spherical type and the composition also changed to dual oxy-sulfides from pure oxides and sulfides as the Ca concentration in the steel was increased up to 36 ppm. The amount of Pure MnS sulfides also reduced significantly after Ca treatment. The ternary phase diagram and stability diagram for the inclusions revealed that 15–25 ppm Ca is the optimal range for the modification of both oxides and sulfides into the desired morphology and composition under the stipulation that the concentration of O in the steel is maintained at or below 50 ppm.

Thermodynamic Formation and Three-dimensional Characterization of MnS–MgAl<sub>2</sub>O<sub>4</sub> Composite Inclusions in Steel

The distribution and morphology of inclusions in steel have an important effect on the quality of steel. It has been proved that the oxide inclusions can be modified into small and dispersed spinel inclusions by adding proper amount of Mg in steel. The MnS-MgAl2O4 composite inclusions are formed with the core of MgAl2O4 inclusions during the solidification process of molten steel, which has deforming ability and can improve the properties of materials steel. However, the investigation of the control of the composite inclusions is limited by the lack of understanding structure of the inclusions. In this study, the Mg treated steel samples were prepared by induction furnace in this study. In the experiment, SEM-EDS was used to characterize the samples, and thermodynamic calculations were used to describe the evolution mechanism of inclusions and MnS-MgAl2O4 composite inclusions formed in steel samples with different Mg contents. The atomic mismatch calculated between MnS and MgAl2O4 proves that they can nucleate effectively. The three-dimensional (3D) morphology of the composite inclusion of MnS-MgAl2O4 in steel samples were observed by using the X-ray Micro-CT in the beamline of BL16U2 at Shanghai Synchrotron Radiation Facility (SSRF). It is proved that MnS and MgAl2O4 phases exist in the form of co-associated, which is valuable for the control of composite inclusions in steel. The current work provide a powerful method to analyze the detailed structure of the composite inclusions in the steel.

Effect of Manganese Sulfide Inclusion Morphology on the Corrosion Resistance and Pitting Corrosion Behavior of Free-Cutting Austenitic Stainless Steel

Effect of Manganese Sulfide Inclusion Morphology on the Corrosion Resistance and Pitting Corrosion Behavior of Free-Cutting Austenitic Stainless Steel

Morphology and Composition Changes in Fluid Inclusions from Quartz under Progressive Deformation: Case Study of a Vein System in the Western Kelyan-Irokinda Fold Zone (Western Transbaikalia)

Abstract —The behavior of fluids during plastic deformation is studied from the morphology and distribution of fluid inclusions in quartz grains of different microstructure types from a vein system controlled by thrusting and strike-slip faulting in the eastern Sayan–Baikal fold area. The analytical work includes electron backscatter diffraction (EBSD) for quartz microstructure and crystallography, as well as Linkam heating-and-freezing analysis and Raman spectroscopy for the composition of fluid inclusions. The studied fluid inclusions are of seven types that differ in morphology and position in the deformed quartz structure. A model is suggested to describe successive structural changes of quartz aggregates during dislocation sliding and subsequent creep-related recrystallization associated with redistribution of fluid. Fluid inclusions undergo qualitative and quantitative changes due to water leakage at all stages of plastic deformation. The changes occur by two main mechanisms: (i) mass transfer during dislocation sliding at medium temperatures and strain rates and (ii) diffusion creep at low strain rates and high temperatures. The contribution of creep increases gradually with temperature, which maintains the interaction of inclusions with migrating grain boundaries.