Metallic Inclusions Research Articles

The Toughness of High-Strength Steel Weld Metals

Low-temperature phase transformation (LTPT) welding consumables are a new class of welding wires developed to mitigate hydrogen-induced cracking in the welding of high-strength steels without preheating or postweld heat treatment. LTPT weld metals have a high strength, but their toughness needs further investigation. LTPT weld metals predominately contain a martensite microstructure, which is necessary to achieve high strength; however, martensitic weld metals containing oxide inclusions have relatively poor toughness. Three welding processes — gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and hot wire GTAW — were investigated. Optical microscopy, scanning electron microscopes, and transmission electron microscopes were employed for characterization. The role of the shielding gas in the formation of oxide inclusions in LTPT weld metals was investigated. The formation of oxide inclusions in the weld metals was related to the CO2 in the shielding gas. When 100% Ar or a pure inert shielding gas mixture was used for all three welding processes, oxide inclusions were greatly reduced, and the weld metal toughness improved considerably, matching the base metal toughness. The mechanism by which inclusions promote fracture propagation in the weld metal was proposed.

Metallic networks and hydrogen compensation in highly nonstoichiometric amorphous In2O3−x

The unique response of amorphous ionic oxides to changes in oxygen stoichiometry is investigated using computationally intensive ab initio molecular dynamics simulations, comprehensive structural analysis, and hybrid density-functional calculations for the oxygen defect formation energy and electronic properties of amorphous ${\mathrm{In}}_{2}{\mathrm{O}}_{3\ensuremath{-}x}$ with $x=0$--0.185. In marked contrast to nonstoichiometric crystalline nanocomposites with clusters of metallic inclusions inside an insulating matrix, the lack of oxygen in amorphous indium oxide is distributed between a large fraction of undercoordinated In atoms, leading to an extended shallow state for $x<0.037$, a variety of weakly and strongly localized states for $0.074<x<0.148$, and a percolation-like network of single-atom chains of metallic In-In bonds for $x>0.185$. The calculated carrier concentration increases from $3.3\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.037$ to $6.6\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.074$ and decreases only slightly at lower oxygen content. At the same time, the density of deep defects located between 1 and 2.5 eV below the Fermi level increases from $0.4\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.074$ to $2.2\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.185$. The wide range of localized gap states associated with various spatial distributions and individual structural characteristics of undercoordinated In is passivated by hydrogen that helps enhance electron velocity from $7.6\ifmmode\times\else\texttimes\fi{}{10}^{4}$ to $9.7\ifmmode\times\else\texttimes\fi{}{10}^{4}$ m/s and restore optical transparency within the visible range; H doping is also expected to improve the material's stability under thermal and bias stress.

Multifunctional liquid metal polymer composites

AbstractLiquid metal polymer composites are an emerging class of functional materials with potentially transformative impacts in wearable electronics, soft robotics, and human‐computer interactions. By employing different processing methods, room temperature liquid metal inclusions can be embedded in insulating polymers like elastomers to incorporate functional properties of metals while the matrix remains soft and stretchable. These solid–liquid composites offer an interesting, yet complex multifunctional material system. In this review, we present an exclusive overview of the synthesis methods, structural and functional properties, and applications of gallium‐based liquid metal polymer composites. Common methods to control the size of liquid metal inclusions and their interaction in polymers are discussed. Moreover, the effect of liquid metal microstructures on the overall properties of the composites is summarized. We also highlight the new trends in terms of material composition, printing process, and novel applications of liquid metal polymer composites in intelligent systems.

Individual and Binary Mixture Toxicity of Five Nanoparticles in Marine Microalga Heterosigma akashiwo.

The investigation of the combined toxic action of different types of nanoparticles (NPs) and their interaction between each other and with aquatic organisms is an important problem of modern ecotoxicology. In this study, we assessed the individual and mixture toxicities of cadmium and zinc sulfides (CdS and ZnS), titanium dioxide (TiO2), and two types of mesoporous silicon dioxide (with no inclusions (SMB3) and with metal inclusions (SMB24)) by a microalga growth inhibition bioassay. The counting and size measurement of microalga cells and NPs were performed by flow cytometry. The biochemical endpoints were measured by a UV-VIS microplate spectrophotometer. The highest toxicity was observed for SMB24 (EC50, 3.6 mg/L) and CdS (EC50, 21.3 mg/L). A combined toxicity bioassay demonstrated that TiO2 and the SMB3 NPs had a synergistic toxic effect in combinations with all the tested samples except SMB24, probably caused by a “Trojan horse effect”. Sample SMB24 had antagonistic toxic action with CdS and ZnS, which was probably caused by metal ion scavenging.

Eddy-current flow meter response to spherical non-conductive inclusions travelling in a liquid metal

In this paper, we address the problem of characterizing the size and position of a spherical non-conductive inclusion in a conductive material. The characterization is done using an Eddy-Current Flow Meter (ECFM), a device usually used to measure the flow rate of liquid metals, but which is also sensitive to the second gaseous phase. ECFM responses to the passage of inclusions in a quiescent liquid metal are computed numerically. The signal amplitude and phase variations are analyzed for inclusions of different radii and radial positions travelling in the pipe. Two parameters are introduced to characterize these variations: the maximum amplitude of the ECFM signal and its corresponding phase. It is shown that a unique relation exists between these parameters and the size and position of the inclusion. The ECFM signal thus provides enough information to determine the size and position of the inclusions by means of an inverse method. This provides valuable information for low void fraction measurement in industrial liquid metal flows. Tables 2, Figs 5, Refs 10.

Experience in the use of modern methods for the study of non-metallic inclusions in low-alloy rolled metal

Experience in the use of modern methods for the study of non-metallic inclusions in low-alloy rolled metal

Correlating electronegativity in bimetallic oxygen carriers for chemical looping combustion

Metallic tailoring of oxygen carrier plays a crucial role within chemical looping combustion (CLC) applications, which can be correlated to the redox reaction enhancement and sustainability. Such attributes arise from the electric valence of the material constituents, which can bring about superior oxygen vacancy and structural stability. In the concurrent study, the role of electronegativity of the bimetallic carriers upon CLC performance was scrutinized based on various bimetallic metal oxides composition. Two metallic systems were examined in the current study: Iron based oxides and copper-based oxides, where the secondary metallic element within each of the examined oxide carrier is composed of one of the 5 metallic elements, predefined for the purpose of electronegativity variation. The secondary metallic element include: Calcium, Lanthanum, Magnesium, Manganese, and Chromium. Several gas byproducts were monitored during the course of the CLC reaction, via mass spectrometer, in order to quantify the variations incurred as a result of different metallic composition inclusion. Additionally, electron microscopic techniques, such as the SEM, were utilized in the study, so as to visualize the structural alteration of sintered materials. The experimental results indicate a higher reactivity with the fuel at a higher electronegativity difference within the bimetallic structure, in the case of iron-based oxide system. Also, copper-based oxide system was associated with higher carbon dioxide production with higher selectivity, relative to iron-based oxide systems.

Magneto-Optical Spectra of Magnetic Photonic Crystal with Composite (SiO2-Au) Layer

The resonant enhancement of magneto-optical effects due to structure modes arising at the boundary of magnetic photonic crystal [TiO2 / SiO2] m / iron garnet / SiO2 / (SiO2-Au), in which the upper layer (SiO2-Au) is a composite layer of SiO2 with metallic Au nanoscale inclusions, and iron garnet is a bi-layer of composition Bi1.0Lu0.5Gd1.5Fe4.2Al0.8O12 / Bi2.3Dy0.7Fe4.2Ga0.8O12, has been considered by modelling of 4×4 transfer matrix method.

Revealing the complexity of high temperature oxide formation in a 38Ni-21Cr-20Fe-13Ru-6Mo-2W (at. %) multi-principal element alloy

The oxide film formed on a corrosion-resistant multi-principal element alloy 38Ni-21Cr-20Fe-13Ru-6Mo-2W (at. %) was characterized via transmission electron microscopy and atom probe tomography. Oxidation in air at 600°C for 1080 minutes resulted in a complex, layered film with multiphase inner and outer oxide scales, and localized recrystallization in the underlying base alloy. The outer oxide scale is dominated by two phases: a Ni-Fe spinel (≈NiFe2O4) and a Ni-rich monoclinic phase (NiMoO4). The inner oxide consists of a near surface Ni-Fe-Cr spinel and RuO2, and semi-continuous Cr2O3 with oxygen-rich Ru-Mo metal inclusions. Local recrystallization and concomitant elemental partitioning in the base alloy was influenced by a high dislocation density in the as-prepared sample surface.

Microstructure features and formation mechanism in a newly developed electroslag welding

Electroslag welding (ESW) is known to show higher heat input than electrogas welding (EGW), resulting in poor low-temperature toughness. However, a newly developed ESW (dev. ESW) method using low-resistivity slag bath exhibited excellent low-temperature toughness as a result of lower effective heat input than conventional EGW, as demonstrated by the faster cooling rates measured in weld metals and estimated using finite element method analyses. This led to much shallower molten pool in the dev. ESW, resulting in much finer columnar grains and thinner centerline axial grains. High cooling speed in the dev. ESW method appeared to contribute to increased acicular ferrite proportion. The uniform microstructure with large acicular ferrite proportion and small number of inclusions in the weld metal permitted the dev. ESW weld metal to possess little variation in Charpy impact energy across the center of weld metal.

Modification of the remaining useful life equation for pipes and plate processing of offshore oil platforms

Incorporation of an adequate maintenance program related to the ageing of industrial facilities occurring in offshore oil platforms is vital to reduce costs and avoid catastrophic failures. In the present work, a set of components (i. e. pipes, plates, and elbows) were removed from offshore oil platforms from different processes with 20 years of uninterrupted operation. The component's characterization consisted of chemical composition, microstructure, and mechanical properties. A collection of results was made to evidence several indicators to keep track of crucial deviations of processing components. These indicators should be taken into account when actions must be taken to guarantee the mechanical integrity of the studied components. From 68 studied samples, 16 samples did not fulfill their chemical composition, 37 samples showed a banded microstructure, 36 samples did not fulfill their mechanical properties, and all of them showed the presence of non – metallic inclusions associated with a pitting corrosion mechanism. These results compilation allow for modification of the remaining useful life equation, RUL, (used to calculate the remaining useful life of a variety of asset types). Thus, the outcome of the modified equation indicates where and when it is necessary to remove components before its catastrophic failure.

Recognition of surface defects of rolled steel in sheets by application micro-X-ray spectral analysis

Surface defects of sheet rolled products have a significant impact on its quality, performance and further processing of products, for example, on application of a protective anticorrosive coating. Therefore, the elimination of such defects and their accurate identification is an important aspect of sheet rolling production. Reducing the rejection of metal for surface defects enables to get a significant technical and economic effect. Investigation of the causes of defectiveness of the surface of sheet rolled products will make it possible to determine the source of the appearance of the defects and methods to prevent them. Determination of the nature and morphology of surface defects, the sources of which being metallic and non-metallic inclusions, as well as remnants of slag surface layer, scales from metallurgical and rolling stages, rolled into the surface of a hot-rolled sheet, is often difficult, since the appearance of the defects is very similar. It was shown that application of a scanning electron microscope (SEM) with micro-X-ray spectral analysis (MXSA), thermodynamic analysis makes it possible to determine the chemical composition of micro-areas and associate it with the end-to-end technology of sheet production. The article presents the results of identifying surface defects of cold-rolled sheet steel.

Self‐Metalation of Porphyrins at the Solid–Gas Interface

AbstractSelf‐metalation is a promising route to include a single metal atom in a tetrapyrrolic macrocycle in organic frameworks supported by metal surfaces. The molecule–surface interaction may provide the charge transfer and the geometric distortion of the molecular plane necessary for metal inclusion. However, at a metal surface the presence of an activation barrier can represent an obstacle that cannot be compensated by a higher substrate temperature without affecting the layer integrity. The formation of the intermediate state can be facilitated in some cases by oxygen pre‐adsorption at the supporting metal surface, like in the case of 2H‐TPP/Pd(100). In such cases, the activation barrier can be overcome by mild annealing, yielding the formation of desorbing products and of the metalated tetrapyrrole. We show here that the self‐metalation of 2H‐TPP at the Pd(100) surface can be promoted already at room temperature by the presence of an oxygen gas phase at close‐to‐ambient conditions via an Eley–Rideal mechanism.

Self-Metalation of Porphyrins at the Solid-Gas Interface.

Self‐metalation is a promising route to include a single metal atom in a tetrapyrrolic macrocycle in organic frameworks supported by metal surfaces. The molecule–surface interaction may provide the charge transfer and the geometric distortion of the molecular plane necessary for metal inclusion. However, at a metal surface the presence of an activation barrier can represent an obstacle that cannot be compensated by a higher substrate temperature without affecting the layer integrity. The formation of the intermediate state can be facilitated in some cases by oxygen pre‐adsorption at the supporting metal surface, like in the case of 2H‐TPP/Pd(100). In such cases, the activation barrier can be overcome by mild annealing, yielding the formation of desorbing products and of the metalated tetrapyrrole. We show here that the self‐metalation of 2H‐TPP at the Pd(100) surface can be promoted already at room temperature by the presence of an oxygen gas phase at close‐to‐ambient conditions via an Eley–Rideal mechanism.

Stretchable, Soft, and Variable Stiffness Elastomer foam with Positive and Negative Piezoresistivity Enabled by Liquid Metal Inclusion

AbstractStretchable and soft piezoresistive composites are appealing for application to tactile sensors, artificial skin, and wearable electronics. The ability of the composites to deform the geometries when they are strained can allow the electrical behavior of the composites to be manipulated. Although rigid metal and semiconductor inclusions have been utilized to create piezoresistive composites, they limit the degree of mechanical deformation. Here, liquid metal (gallium, melting point ≈ 29.7 °C) inclusion into elastomeric foam substrate with 3D open cell morphologies is utilized. Gallium is a fluidic conductor, thus it is possible to infiltrate the liquid metal into the 3D interconnected pore, resulting in soft, stretchable, and shape reconfigurable conductive composites that can change shape and function in response to external stimuli. Applying strain can enable deformation of the liquid metal, generating changes of electrical resistance. Interestingly, it is found that this piezoresistivity of the composite can be positively and negatively manipulated by adjusting the geometries of the liquid metal in the foam. Furthermore, the liquid metal in the elastomeric foam can be reversibly actuated by applying compressive force, resulting in manipulation of the restorative electrical activity of the composites.

Computer Simulation of Composites Consisting of Piezoceramic Matrix with Metal Inclusions and Pores

Computer Simulation of Composites Consisting of Piezoceramic Matrix with Metal Inclusions and Pores

Solving the problems of underwater mecha-nized and automatic arc welding of various metal structures with a wet method

A complex of problems related to semi-automatic and automatic underwater wet welding, concerning both equipment and ways of implementation of arc process, has been considered. An analysis of existing developments in the considered field of welding has been carried out, and the most rational designs of semi-automatic machines for welding with flux-cored electrode wire have been revealed. It is shown that the semiautomatic device with a submerged block is the most rational design; the feeding mechanism, placed in the block, has its own additional body, filled with insulating-lubricating liquid, in which the drive motor is submerged. It is noted that a peculiarity of welding-in-fusion in aqueous medium is unpleasant formation of joints on the vertical plane. The most effective ways of improving semi-automatic and automatic machines related to modulated processes and processes with controlled pulse feeding of electrode wire are presented. It is shown that lately the most effective choice of electric motor is its valve design. At the same time, the feeding mechanism in the gearless version is possible. Specially designed computerized control and regulation system is used for realization of semiautomatic machine's work cycle and the chosen algorithm of electrode wire feeding. The results of electrode wire pulse feeding application on properties of welded joints are given. It is determined that characteristics of pulse feeding (frequency, duty cycle) influence geometric characteristics of the weld, as well as strength properties, in particular yield and time resistance limits, which, among other things, is caused by reduction of nonmetallic inclusions in the weld metal and the weld zone. External types of beads welded in aqueous medium on the vertical plane are given, it is obvious that formation when using pulse and modulated modes is significantly better than when conducting electric arc process with conventional feeding of the electrode wire. The ways of further improvement of the equipment for welding in aqueous medium by a wet method are shown. One of the most promising ways to improve technical and technological capabilities of mechanized equipment for welding in aqueous medium is the creation and application of systems with combined influence on the process.

Fracture failure analysis of metal materials by visual inspection and destructive testing

A methodology is presented to perform fault analysis in metal materials that have failed due to fracture. The proposed method was applied to the study of a fracture presented in the jaw supporting the test pieces in a universal machine used for mechanical tests on materials. The analysis was structured in two stages, initially a visual inspection of the failed element, followed by a series of destructive tests to identify the characteristics of the material and the occurrence of the failure. Visual inspection identified the morphology of the material in the fault zone with gloss and with a characteristic cleavage fracture shape corresponding to a fragile and brittle material. With arc and spark spectrometry the composition of the material was identified, Metallography showed the formation of martensite typical of medium-carbon steels subjected to thermal hardening and scanning electron microscopy identified the precipitation of carbides at the grain boundary, as well as the presence of gaps and other metallic and non-metallic inclusions in the microstructure. The proposed methodology allowed to characterize the fault and propose an appropriate solution by identifying possible hidden faults solving the root of the problem.

Diamond growth and characteristics in the metal-silicate-H2O-C system at HPHT conditions

The detailed phase composition and characteristics of diamond crystals grown in the metal-silicate-H2O-C system at 5.5 GPa and 1385 °C are reported in this paper. The conversion efficiency of the graphite-to-diamond in the metal-silicate-C system is lower than that in the metal-C system, which significantly decreases the growth rate of crystal. As the Mg2Si3O8·5H2O content increases to 1.5 wt%, growth pits and {110} related features of trigonal pyramids, skeletal structure, rhombic dodecahedron, and {110} dendrites exhibit in sequence. Simultaneously, the content of graphite and metal inclusions inside the crystal increases. These systematic changes are accompanied by the appearance of CH, CO, and CO bonds and a decrease of nitrogen content from ⁓210 ppm to ⁓60 ppm. It is speculated that H2O will further decompose and bond with carbon atoms and finally enter the diamond structure. The formation of CH and CO bonds will terminate the extension of the three-dimensional network of CC bonds. These defects will accumulate along the [111] direction and form {110} related characteristics. These chemical bonds also compete with the nitrogen in the system during entering into the diamond lattice. Our experimental model may provide implications for the morphology and formation environment of natural diamonds.

Numerical investigation of the effects of partial metallization at the pore surface on the effective properties of a porous piezoceramic composite

This paper presents a numerical homogenization analysis of a porous piezoelectric composite with a partially metalized pore surface. The metal layers can be added to the pore surfaces to improve the mechanical and electromechanical properties of ordinary porous piezocomposites. Physically, constructing that composite with completely metalized pore surfaces is a challenging process, and imperfect metallization is more expected. Here, we investigate the effects of possible incomplete metallization of pore surfaces on the composite’s equivalent properties. We applied the effective moduli theory, which was developed for the piezoelectric medium based on the Hill–Mandel principle, and the finite element method to compute the effective moduli of the considered composites. Using specific algorithms and programs in the ANSYS APDL programming language, we constructed the representative unit cell element models and performed various computational experiments. Due to the presence of metal inclusion, we found that the dielectric and piezoelectric properties of the considered composites differ dramatically from the corresponding properties of the ordinary porous piezocomposites. The results of this work showed that piezocomposites with partially metallized pore surfaces can have a higher anisotropy, compared to the pure piezoceramic matrix, due to the defects in metal coatings.