Chemical Range of Stability for Self-Dusting Ladle Furnace Slags and Destabilizing Effect of Sulfur

Ladle furnace slags are characterized by volumetric expansions associated with the transition of dicalcium silicate (C2S) from β to γ phase, which generates fine dust during cooling, causing handling and storage issues that further reduce their recycling opportunities. The present work focuses on the effect of slag basicity on dusting and the role of sulfur on slag stability. Seven synthetic ladle slag precursors were made by mixing lime, magnesia, quartz and alumina in different proportions to match effective industrial compositions, increasing the binary basicity and keeping the ternary and quaternary indexes unchanged. Samples were heated to 1500 °C for 15 min and monitored during air cooling (< 5 °C/s) through thermocouples and camera to characterize the behavior, temperature, and time interval of dusting. The cooled samples were characterized chemically, mineralogically and morphologically. Starting from the chemistry of a self-stabilized slag, five additional slag precursors, characterized by increasing amounts of S, were created and analyzed using the same procedures. Experimental evidence showed the presence of three different dusting behaviors (stable, partial and complete) and stabilization of the slag once an optical basicity of 0.748 or higher was reached. In addition, mayenite was identified as the main phase capable of suppressing the β to γ transition by exerting hydrostatic pressure on C2S. Finally, although S can stabilize the β phase when dissolved in it, after saturation it precipitates as CaS, which can react with mayenite, locally decreasing the optical basicity and allowing dusting. Graphical Abstract: [Figure not available: see fulltext.]

Processing and characterization of dual phase steel foam

Porous materials featuring cellular structures are known to have many interesting combinations of physical and mechanical properties. Some of them have been extensively used in the transportation field (i.e. balsa wood). Steel foams presented promising theoretical properties for both functional and structural applications in transportation, but processing of such a kind of foams is complex due to their high melting point. Recently a technique for processing Cu-based alloys open-cell foams through the molten metal infiltration of a leachable bed of amorphous SiO2 particles was proposed. A variation of the proposed technique that uses SiC particles as space holder is now presented and was recently successfully applied for dual phase steel foam processing. Results from a processing of dual phase DP500 steel foams, including some morphological, micro-structural and mechanical characterization, are here presented

Characterization and Comparison of Single VAR-Remelted and Double VAR-Remelted Ingots of INCOLOY ® Alloy 925

Alloy 925 is a nickel-based superalloy usually produced by Electric Arc Furnace (EAF), followed by Argon Oxygen Decarburization (AOD) and Vacuum Arc Remelting (VAR). It can undergo to one VAR remelting (EAF-AOD-VAR) or, if necessary due to process instabilities, two VAR remelting (EAF-AOD-VAR-VAR). The characterization of A925 ingots remelted one or two times after forging and aging was carried out to enhance differences. The VAR remelting rate of single- or double-remelted samples was correlated to metallurgical and mechanical properties. The microstructure observation revealed a higher quantity of MC, M23C6 and TiN precipitates (both inter- and intragranular) in single-remelted samples: the intergranular ones increase in quantity going from the ingot center position to the external one where cluster of titanium nitrides were detected. The higher presence of intergranular precipitates causes a high deterioration of impact toughness (71.1 ± 12.7 vs 90.5 ± 7.1 J) and lateral expansion (0.91 ± 0.18 vs 1.14 ± 0.07 mm). On the other hand, the number of remelting does not affect other tensile properties and hardness. Therefore, the different behavior of forged ingots at single and double remelting are not related to the number of remelting and remelting rate. On the other hand, the slightly lower toughness of single-remelted forged ingots can be corelated to defects derived from casting

Mechanical and tribo-metallurgical behavior of 17-4 precipitation hardening stainless steel affected by severe cold plastic deformation: a comprehensive review article

This article comprehensively reviews the mechanical properties and tribo-metallurgical behavior of 17-4 precipitation hardening stainless steel (17-4PH SS) during and after cold plastic deformation. Referring to the scientific literature, stainless steels are one of the few types of ferrous alloys which could be appropriately set up through cold working processes in the forms of sheets or other shapes. Likewise, some other metal alloys such as mild low-carbon-based steels, copper and its alloys, aluminum alloys, and some others are the few types of metal alloys which have this capability. On the other hand, in engineering applications, there are several types of mechanical failures, which must be taken into account to investigate the mechanical behavior and tribo-metallurgical properties of any targeted materials. For example, corrosion resistance, wear resistance, and fatigue failure are investigated according to the microstructural studies, comprising of the grain size, grain boundaries, orientations, dislocations, and so on. Based on the published results, focusing on 17-4PH SS, one of the most main effective factors on mechanical and tribo-metallurgical performance is the grain size. Also, the favorable balance of two mechanical properties of strength and ductility has been reported as a dilemma in the materials science, and the problem delineates upon the limitations of numerous structural materials potentials. Following the failure analysis of the materials, in order to diminish the damages caused by fretting fatigue some methods such as ultrasonic processes are applied for the treatment of 17-4PH SS via changing the microstructure, residual stress, and other parameters. Also, through the other cold deformation technologies, the nanostructured surface layer with highly upgraded mechanical properties of several ultrasonic surface rolling process-treated 17-4PH SS has been obtained. To this end, such cold working processes on 17-4PH SS and their subsequent results are elaborated in this review paper. Graphical abstract: [Figure not available: see fulltext.

Therapeutic effects of chlorhexidine digluconate (CHX) in laborers with untreated gingivitis

published_or_final_versio

Presence of A. actinomycetemcomitans and P. gingivalis in young Chinese adults

published_or_final_versio

Microstructural investigation on an Al 6061 T6 alloy subjected to ballistic impact C

Ballistic impact generates significant modifications in the microstructural patterns. High strain rate and local high temperature conditions work together in opposite way: the first causes strain hardening, while the second factor produces softening. Moreover, after the impact, the cooling process is responsible of other local modifications on the arrangement of dislocations and precipitates. Therefore an experimental analysis on Al 6061 T6 cut from the edge of a component subjected to ballistic impact has been carried on in order to investigate on the microstructural modifications. Considerations about the influence on the mechanical behavior and on the fracture propagation are reported. The crystallographic textures and the misorientation featuring the grains play in fact a significant role in the fracture mechanism. The comparison between the texture situation before and after the impact can allow to evaluate the localized straining of the material and to point out its dissipation efficiency as a function of the distance from the damaged surfaces © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM1

Effect of cold drawing reduction rate on edge-to-center-characterized microstructure and orientation alongside residual stresses in conjunction with magnetic properties of low-carbon high-alloy ferromagnetic steel

In the current research, the effect of cold drawing reduction rate (CDRR) of 15% and 45% and the required subsequent isothermal static recrystallization annealing heat treatment (ISRAHT) on the microstructures, textures, residual stresses, and magnetic properties of ferritic/ferromagnetic stainless steel (FSS), EN 1.4106, are investigated by a series of experimental analyses. The study is carried out by the theoretical well-known model of Johnson-Mehl-Avrami-Kolmogorov (JMAK) in conjunction with aforesaid properties. According to the results, by increasing the CDRR, the recrystallization fractions (RF) become faster in accordance with the JMAK theory. Such an increment also affects more fragmented and elongated grains, which leads to provide smaller grains in size. However, by the effect of slow cooling process (SCP), the grain growth is another noticeable part of study. Likewise, the effects of CDRR and the subsequent ISRAHT find to be beneficial for the evolution of microstructures, textures, and relief of residual stresses, and better performance of magnetic behavior. For instance, higher relative magnetic permeabilities approximately above 1000 causes to reach residual stresses closer to zero. The cold-drawn FSSs are consisted of the α-fibre texture, which is close to {2 2 3} 〈1 1 0〉 and {1 1 1} 〈1 1 0〉, with higher intensity while by gradual higher recrystallization, the orientation tendency to {1 1 1} 〈0 1 1〉 of γ-fibre are formed following to the more distributed texture with lesser intensity. The findings display that while the recrystallization process addresses the formation of new grains, resulting in the more equiaxed grains, more well-aligned textures are also achieved in respect to the lower misorientation uniformity density and even with more distributed clusters

Thermodynamics of a mixed quantum-classical Heisenberg model in two dimensions

We study the planar antiferromagnetic Heisenberg model on a decorated hexagonal lattice, involving both classical spins (occupying the vertices) and quantum spins (occupying the middle of the links). This study is motivated by the description of a recently synthesized molecular magnetic compound. First, we trace out the spin 1/2 degrees of freedom to obtain a fully classical model with an effective ferromagnetic interaction. Then, using high temperature expansions and Monte Carlo simulations, we analyse its thermal and magnetic properties. We show that it provides a good quantitative description of the magnetic susceptibility of the molecular magnet in its paramagnetic phase.Comment: Revtex, 6 pages, 4 included postscript figures, fig.1 upon request to [email protected] . To appear in J. of Physic C (condensed matter

Mechanical-metallurgical-corrosion behavior of Cr-Si-S-C ferritic/ferromagnetic stainless steel, known as AISI 430F, before and after isothermal recrystallization annealing

The research investigates the mechanical and corrosion behavior of Cr-Si-S-C ferritic stainless steel (FSS), known as EN1.4105, which is equivalent to AISI430F. The static isothermal recrystallization annealing is applied to the cold-drawn (CD) materials with two different reduction rates (RRs) of 20 and 35%, under various conditions of soaking temperature and incubation time, which provide 42 unique specimens. The microstructures of CD and annealed materials are characterized by using the electron backscatter diffraction method. X-Ray diffraction analysis alongside scanning electron microscopy linked with energy-dispersive X-ray spectroscopy are also employed to scrutinize the precipitation of any secondary phases, morphologies, and the related chemical compositions. Two different corrosive chlorinated and acidic electrolyte solutions are used for the potentiostatic-based corrosion tests to investigate the passivation kinetics. The results show that the higher RR, which provides faster recrystallization, results in a higher scale of non-hardenable materials. In addition, the effects of RR and annealing conditions are found to have an impact on the corrosion resistance. Moreover, the material exhibits varied behavior in terms of both passivation layer formation as the immersion in the sulfuric acid electrolyte solution (SAES) and active electrochemical behavior immersing in sodium chloride electrolyte solution (SCES). However, this material shows lower corrosion current density and higher corrosion potential in the SCES compared to the SAES medium. The comprehensive findings underscore the intricate relationship between reduction rates, annealing conditions, microstructural evolution, and corrosion behavior in this FSS. The observed trends provide valuable insights for optimizing material performance and corrosion resistance in practical applications. Graphical abstract: [Figure not available: see fulltext.]