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Alloying Elements (alloying + element)
Selected AbstractsChemical composition of new copper alloys for machining and its effect on their susceptibility to corrosion crackingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2007B. Eremiá Zinc-containing copper alloys, the so-called ,,+,, brasses, are commonly used in contact with potable water. These materials are alloyed with lead to improve machinability. In wrought special brass alloys, reducing the content of this alloying element or replacing it with alternative alloying additions may give rise to a new type of machinable copper alloys which differ from the original alloys by their contents of other modifier elements such as Si (or possibly, Mg, Bi, and P). These alloys have a very low content of lead required for the break-up of chips during machining. Even though these types of brass exhibit a very good machinability, the effects of their chemical composition on the resistance of the alloy to corrosion cracking have not yet been given sufficient attention. This paper aims to present an assessment of three new types of machinable copper alloys regarding their susceptibility to stress corrosion cracking, in comparison to that of the lead-alloyed variety, in 0.05 M NaCl, NaNO2, and Na2SO4 solutions. The slow strain rate test has been used for this purpose, and its results were correlated with metallographic evaluation of the number and depth of the cracks observed on the test specimen surfaces on completion of the test. [source] Influence of the mode of introduction of a reactive element on the high temperature oxidation behavior of an alumina-forming alloy.MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2004Part I: Isothermal oxidation tests Abstract Different modes of introduction of yttrium have been tested with regard to the influence on the high temperature oxidation behavior of a FeCral alloy. Y2O3 sol-gel coatings, Y2O3 metal-organic chemical vapor deposition (MOCVD) coatings, implanted yttrium ions and yttrium as alloying element (0.1 wt.%) in the same Fe-20Cr-5Al alloy were oxidized at 1100°C in air under atmospheric pressure. Whatever the mode of introduction of the reactive element, the oxidation rates were not decreased compared to the oxidation rate of the blank specimen. The observation of the oxidized surface indicated that the alumina scale largely spalled from the blank alloy. Spallation was reduced for the Y2O3 sol-gel coated, the Y2O3 MOCVD coated alloys and the yttrium ion implanted steels. The Y-containing alloy did not exhibit any detachment of the oxide scale, indicating the best high temperature oxidation behavior, at least from the viewpoint of scale adherence. [source] The effect of alloying elements on the crystallization behaviour and on the properties of galvanized coatingsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2004G. Vourlias Abstract The influence of the alloying elements on the interface reactions of zinc coatings during the galvanization process was examined. These reactions affect the crystallization and the structure and properties of the outer layer of the coatings. Depending on the type and concentration of the alloying additions in the galvanizing bath differences were induced in the crystallization process of the Fe-Zn phases. It was found that both the concentration and the distribution of the alloying elements played an important role in the growth of the phases. The formation of the phases and the distribution of the alloying elements in the coatings were determined using X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) associated with an Energy Dispersive X-Ray Spectroscopy (EDS) analysis. Finally the behaviour of the galvanized coatings was examined under accelerated salt spray corrosion conditions. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influences of passivating elements on the corrosion and biocompatibility of super stainless steelsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Young-Ran Yoo Abstract Biometals need high corrosion resistance since metallic implants in the body should be biocompatible and metal ion release should be minimized. In this work, we designed three kinds of super stainless steel and adjusted the alloying elements to obtain different microstructures. Super stainless steels contain larger amounts of Cr, Mo, W, and N than commercial alloys. These elements play a very important role in localized corrosion and, thus, their effects can be represented by the "pitting resistance equivalent number (PREN)." This work focused on the behavior which can arise when the bare surface of an implant in the body is exposed during walking, heavy exercise, and so on. Among the experimental alloys examined herein, Alloy Al and 316L stainless steels were mildly cytotoxic, whereas the other super austenitic, duplex, and ferritic stainless steels were noncytotoxic. This behavior is primarily related to the passive current and pitting resistance of the alloys. When the PREN value was increased, the passivation behavior in simulated body solution was totally different from that in acidic chloride solution and, thus, the Cr2O3/Cr(OH)3 and [Metal oxide]/[Metal + Metal oxide] ratios of the passive film in the simulated body solution were larger than those in acidic chloride solution. Also, the critical current density in simulated body solution increased and, thus, active dissolution may induce metal ion release into the body when the PREN value and Ni content are increased. This behavior was closely related to the presence of EDTA in the simulated body solution. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Glass forming ability and nanocrystallization kinetics of Fe65Nb10B25 metallic glassesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010J. Torrens-Serra Abstract In this work the mechanisms controlling the nanocrystallization kinetics of the Fe65Nb10B25 metallic glasses have been determined by the combination of the analysis microstructural data from XRD and TEM, and the kinetic analysis performed using the Master Curve method of the continuous heating and isothermal calorimetric curves. The results show that the transformation starts by the nucleation and interface controlled growth of the Fe23B6 -type phase that changes to diffusion controlled growth as the transformation advances until is stopped by the soft-impingement effect. The transformation is modeled in the framework of the Kolmogorov,Johnson,Mehl,Avrami (KJMA) theory using constant activation energy expressions for the nucleation frequency and interface-controlled growth and taking into account the reduction of those quantities with the transformed fraction due to the change in the matrix composition using a mean-field approximation. The parameters of the modeling are determined from the coupling between the isothermal and constant heating rate calorimetric analysis and from the quantitative analysis of microstructural data. This is the outset for the determination of the viscosity, driving force for crystallization, and interfacial energy when replacing the constant activation energy expressions by the classical nucleation and growth ones. Both the glass forming ability in Fe,Nb,B based bulk metallic glasses and the temperature dependence of the interfacial energy are discussed in terms of the influence of the minor alloying elements. [source] Influence of alloying elements on the structure and corrosion resistance of galvanized coatingsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2004G. Vourlias Abstract Carbon steel samples were galvanized by the hot-dip method in zinc baths containing 0.5 or 1 wt% aluminum, copper, tin, nickel, and/or lead. Bath temperature ranged from 450 to 480 °C. The samples were examined using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of the alloying elements on the formation of the different phases and on the diffusion process is discussed. In order to study the kinetics and the mechanism of corrosion of these materials, corrosion experiments were carried out in a simulated environment of accelerated atmospheric corrosion conditions, for which a special chamber (Salt Spray Chamber , Alternative Climate Test Chamber) of type SC-450 was used. The corroded samples were examined using optical microscopy, SEM and XRD. Chloride and oxide phases, which penetrated the materials to different depths from the surface, were revealed. Finally, useful conclusions were drawn which help to control the factors of the corrosion behavior of the examined materials in a marine atmosphere. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||