The aim of this research was to determine the factors affecting the metallurgical quality of cast iron during serial production of castings using a campaign cupola and a holding furnace. The problem ...to be solved, which was to obtain cast iron with the required mechanical properties while reducing the internal porosity, results from the foundry’s need to increase the metallurgical quality of the alloy. The increasing difficulty and complicated constructions of castings, for which it is not possible to introduce risers at the stage of technological design, make the stage of proper preparation of cast iron the only way to obtain castings without shrinkage defects. The article presents the results of the study of physicochemical and mechanical properties, microstructure and shrinkage tendency of ductile iron depending on the charge materials used, the amount of Mg used during spheroidization and the type of final inoculants. Step castings and wedge tests were produced on a vertical molding line. The spheroidization was carried out by injecting a core wire containing Mg alloy into the cast iron. The final inoculation of 0.2% was performed using a pneumatic dispenser equipped with a vision system to control the effectiveness of the inoculation. The ITACA Meltdeck thermal analysis system was used to study the physicochemical properties of the initial cast iron, and the ITACA X system to analyze the state of the final cast iron on the molding line. Mechanical tests were performed on samples cut from a stepped casting, and microstructure tests were carried out using a light microscope and a scanning electron microscope. The results of thermal analyses show that increasing the share of pig iron at the expense of steel increases the minimum solidification temperature of eutectic, and thus, increases the potential for graphite nucleation in cast iron. Increasing the nucleation potential can be obtained by adding anthracite, FeSi and SiC. A very important factor in obtaining cast iron of high metallurgical quality is the possible limitation during spheroidization of the length of the core wire containing Mg, which is a carbide-forming element. The lower the initial sulfur level, the greater the possibility of reducing the amount of cored wire. The inoculants containing Ce and Bi were the most advantageous final inoculants from the point of view of obtaining the best microstructure parameters and plastic properties of cast iron.
Heredity in the microstructure of cast iron produced solely from scrap (synthetic cast iron) was considered experimentally. The carbon deficiencies were adjusted using anthracite, synthetic graphite ...and petroleum coke as carburisers. The small flakes of anthracite resulted in smaller graphite flakes in the final microstructure, proving that heredity is affected by the carburiser as much as by the particular “pig iron-steel scrap-cast iron” combination.
Cu-based alloys are known for their high corrosion resistance but with a lack of processing ability and vice versa. Here we present a novel alloy design concept realizing Cu-rich high entropy ...conventional alloy (HECA) having exceptional corrosion resistance (Ecorr = - 0.27 V, icorr = 2.83 × 10−6 A/cm2) and work hardenability (strength = 413 MPa, total elongation = 28 %) synergy simultaneously in as-fabricated state. This cocktailing effect in HECA (Cu-12Fe-8Mn-7.5Co-2.5Cr, all in at%) is attributed to the formation of Fe-Mn-Co-Cr containing high entropy phase (HEP) in the Cu-rich matrix. A pronounced two-phase hardening by hetero-deformation induced (HDI) strengthening effect at the HEP/Cu matrix resulted in excellent work hardenability whereas, exceptional corrosion resistance was attributed to delayed corrosion kinetics owing to the preferential corrosion of the Cu-rich phase over HEP in HECA. Thus, Cu-rich HECA overcomes the corrosion-strength ductility dilemma in Cu-rich alloys when compared with classical binary Cu-Fe alloys in an as-fabricated state.
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•A novel alloy design concept realizing Cu rich high entropy conventional alloy (HECA) is realized.•Pronounced two-phase strengthening event at HEP/Cu matrix resulted in excellent strength and ductility.•Exceptional corrosion resistance is attributed to delayed corrosion kinetics by the preferential corrosion of Cu rich phase over high entropy phase (HEP) in HECA.
This study aims to systematically investigate the influence of boron (0–3.0 wt % B) on microstructure and abrasive wear characteristics of high chromium based multi-component white cast iron (Hi-Cr ...MWCI).
As result, the microstructure is mainly composed of martensite matrix and carborides such as M7(C, B)3, M2(C, B), M23(C, B)6. At low load, B can increase the wear resistance of Hi-Cr MWCI owing to the higher volume fraction of M2(C, B). However, it reduces the wear resistance of material due to low the fracture toughness of primary M7C3 or M7(C, B)3 at high load. Therefore it can be concluded that B addition can improve the abrasive wear resistance of Hi-Cr MWCI at low load, but, the opposite tendency will occur at high load.
•Boron can increase the volume fraction and size of carboride.•The shape and stoichiometry of M2(C,B) carboride is altered from fishbone-like to plate-like by 3.0 wt % B.•Boron addition reduce fracture toughness of M7(C,B)3 carboride but its hardness is improved.•The abrasive wear rate is influenced by the matrix and volume fraction of M2(C,B) carboride at low load.•The abrasive wear rate is strongly influenced by the fracture toughness of M7(C,B)3 carboride at high load.
Isomerism of nitratoalkylazoles Bauer, Lukas; Benz, Maximilian; Klapötke, Thomas M. ...
FirePhysChem,
September 2024, Volume:
4, Issue:
3
Journal Article
Peer reviewed
Open access
In the field of energetic materials, traditional materials with high toxicity or other disadvantages are mostly used. There is an urgent need for trinitrotoluene replacements (TNT), which itself is ...toxic and its production is problematic due to red wastewater. New materials should be safe to handle, have good performance, and be inexpensive to synthesize. Nitratoalkylazoles are known to have low melting points and good energetic properties compared to TNT. In this paper, seven energetic compounds are synthesized starting from 5-methyltetrazole, 5-hydroxymethyltetrazole and 4,5-bishydroxymethyltriazole. The nitrates are characterized in terms of their physical, chemical, and energetic properties. Of those seven compounds, five are solid, melting between 27 °C and 110 °C, and two are liquid. Methylation and hydroxyalkylation were performed and discussed extensively. The organic nitrate is introduced in the last step so that the synthesis remains safe and scalable. Correlations between the molecular geometry and the melting points are explained. Calculations indicate detonation velocities that are 6%–11% higher than those of TNT. A discussion of the effect of isomerism on the properties leads to surprising insights and should help focus and accelerate research on the replacement of TNT.
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Highly volatile solid additives have attracted much attention recently because they enhance molecular packing order and possibly solve the problems of poor reproducibility and instability of polymer ...solar cells (PSCs) with solvent additives. The shortcoming is that existing solid additives require thermal annealing (TA) to remove them from the active layer, leading to an increase in the complexity of the device fabrication process and morphology rearrangement problems. This study introduces a commercially available, low‐cost, and highly volatile material, naphthalene (NA), as a solid additive used in PSCs based on PM6: Y6. NA is well mixed with a non‐fullerene acceptor and can restrict excessive aggregation of the donor and acceptor, producing efficiencies comparable to PSCs processed by 1‐chloronaphthalene (CN) solvent additive. As a result, a maximum power conversion efficiency (PCE) of 16.52% for NA‐processed PSC is achieved, higher than that of a PCE of 16.07% for CN‐processed PSC with TA. NA‐processed PSCs exhibit comparable efficiencies (PCE of 16.10%) without TA treatment and higher reproducibility/stability than CN‐processed PSCs. This study demonstrates a low‐cost and excellent volatile solid additive to improve the device performance and the potential for exploring new solid additives that can readily be made volatile without TA.
This work presents a study on commercially available, low‐cost, and highly volatile naphthalene as a solid additive used in polymer solar cells (PSCs). Naphthalene is a promising processing solid additive that can be entirely volatilized without thermal annealing treatment and achieve higher efficiency with improved reproducibility and stability of PSCs.
•Periodic micromechanical models are developed for the nodular cast iron system.•Concurrent ductile and shear damage models are implemented for the phases.•Stress triaxiality is demonstrated to ...deeply influence damage mechanism and failure strain.
This paper presents modeling of the tensile and failure behavior of different nodular cast iron microstructures under variable stress triaxialities. The model is based on a Representative Volume Element (RVE) approach, which reproduces periodic stochastic distributions of nodules within a 3-D cell. Three cast iron matrices, from fully ferritic to fully pearlitic, are considered as representing the various nodular cast iron classes in relation to strength and ductility. Ductile damage and shear damage models are used for ferrite and pearlite, respectively. Several values of stress triaxiality are applied within the RVE. It is found that numerical results support experimental findings in relation to the local strain distribution and damage initiation and accumulation, reproducing macroscopic tensile responses with good approximation. As highlighted by experiments, triaxiality is found to have a strong effect on material ductility and void volume fraction growth.
This study aims to investigate the effects of growing niobium carbide (NbC) particles into intermetallic iron-aluminide (FeAl) coatings on ductile cast iron (SGI) by thermo-reactive diffusion ...technique (TRD). The study compares the corrosion and oxidation behavior of the FeAl-NbC coatings with SGI, FeAl, and NbC coatings. Corrosion tests were conducted through polarization tests in a 3.5 wt% NaCl solution, while oxidation tests were performed at 900 °C for 4, 16, and 64 h. Before and after corrosion and oxidation tests, the coatings were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The findings show that FeAl coatings with NbC particles had lower graphite nodules, porosity, and surface roughness values compared to FeAl coatings. FeAl-NbC composite coatings provided better corrosion and oxidation resistance compared to untreated SGI, FeAl, and NbC coatings. The results of the comparative analysis of FeAl-NbC, FeAl, NbC, and untreated SGI specimens indicate that corrosion resistance in a 3.5 wt% NaCl solution and oxidation resistance at 900 °C followed the order FeAl-NbC > FeAl > NbC > SGI.
•Investigating NbC in FeAl coatings on SGI for corrosion and oxidation•Corrosion tests in 3.5 % NaCl and oxidation tests in air at 900 °C for 4, 16 and 64 h•NbC in FeAl coatings reduced graphite, porosity and improved performance.•Damage in FeAl and SGI started around graphite, while in NbC at grain boundaries.•Increasing oxidation time transformed SGI's Fe2O3 + Fe3O4 to Fe2O3, no change in FeAl-NbC.
The structural and elastic properties of (Fe, Cr, W)sub.7Csub.3 were investigated by first principles. Tungsten doping can improve the ductility and the indentation modulus of (Fe, Cr)sub.7Csub.3 ...carbides. The elastic anisotropy of Msub.7Csub.3 became weaker after tungsten doping. A new carbide (Fesub.3.27Crsub.2.99Wsub.0.74) Csub.3 was found to be a combination of mechanical properties. Tungsten doping is critical for the wear resistance and application of High-Chromium Cast Iron (HCCI). A series of investigations of (Fe, Cr, W)sub.7Csub.3 carbides were performed by first principles calculations and experimental analysis. The calculated results showed that with the increase in tungsten content in Msub.7Csub.3, the equilibrium cell volumes and the density gradually increased, and the formation energy of Msub.7Csub.3 carbides gradually decreased. The TEM results showed that the (Fe, Cr, W)sub.7Csub.3 carbides were (Fesub.3.27Crsub.2.99Wsub.0.74) Csub.3 with a hexagonal structure after adding 2.13 wt % tungsten into laser cladding coatings of High-Chromium Cast Iron with a composition of Fe-26.8 wt % Cr-3.62 wt % C. These results from calculations and in situ nanoindentation show that tungsten doping could improve the ductility and indentation modulus of (Fe, Cr)sub.7Csub.3 carbides, and the composition of (Fe, Cr, W)sub.7Csub.3 was expected to be a high hardness and softness material. The wear test results showed that the wear resistance of tungsten-bearing HCCI was better than ordinary HCCI.
In the present work, it is experimented to reinforce duralumin powder (3 to 7 wt %.)into Al7075 matrix by stir casting technique. Since matrix and reinforcement both have almost similar melting ...temperatures,theleast expensive additive manufacturing metallurgical route seems to be the best fit. In this study, an effort was made to produce the Al7075 matrix composite reinforced with duralumin by a novel stir casting method by coating duralumin powders with nickel which has high temperature melting point compared to reinforcement material. Nickel has goodwettability and avoids undesirable chemical reactions between the reinforcement and matrix at higher temperatures, acting as a protector for both the duralumin and matrix. Since, aging kinetics of duralumin (Al2024) and Al7075 are different, both positively respond to heat treatment in a single stretch for propertyalteration. During stir casting, even though duralumin melts along with the matrix, it will be under the solid protection barrier (coat) of nickel, avoiding dissolution with the Al7075 matrix.To verify the presence of reinforcement duralumin in the matrix and to decide the soundness of the casting produced by stir casting, confirmation tests are made like microstructures with EDS and micro hardness distribution. The microstructure analysis of the compositeshowedan even distribution of nickel coated duralumin in the matrix when the coating thickness of a nickel is greater than 8 µm. The hardness test analysis has shown an improvement in the hardness with the increase in the weight % of the reinforcement. Improvement in the hardness of composites is due to an increase in dislocation number, which shows higher resistance to plastic deformation 2.Statistical analysis has shown that the coating of reinforcement does not have any significant effect on the mechanical properties. The regression equation is fit to determine the hardness of the composite involving the factors within the range of values considered for this study.
