Papers by Keyword: Bronze

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Authors: José M. Gallardo, Francicso Gomez Cuevas, Jesus Cintas, Juan M. Montes
Abstract: As the first step in the restoration process of a Renaissance bronze statue, a comprehensive study of the metallic product was carried out. This paper reports metallographic features and their possible relation to the casting process. Tensile properties are also discussed as they depend on porosity and lead content, what can be useful in the restoration process.
Authors: Ali Gholinia, Ian Brough, John F. Humphreys, Pete S. Bate
Abstract: A combination of electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques were used to obtain 3D EBSD data in an investigation of dynamic recrystallization in a Cu-2%Sn bronze alloy. The results of this investigation show the origin of the nucleation sites for dynamic recrystallization and also elucidates the orientation relationship of the recrystallized grains to the deformed, prior grains and between the dynamically recrystallized grains.
Authors: Nikita Martyushev
Abstract: This paper reports on the use of nanopowders in the coating composition forms in casting blanks from lead bronzes for the petrochemical industry. Influence of composition of used protective separating coating of casting mold on the microstructure castings was investigated. For experimental investigations following coating were selected [1]: the mixture of zirconium dioxide nanopowder with industrial oil and the same composition as it’s, but on the basis of aluminum oxide nanopowder. As the test material multicomponent and lead bronzes were selected. The cooling curves castings using coatings of different compositions by means the developed device thermograph were constructed using techniques developed by the authors. The study results showed that the greatest reduction in the cooling rate at the time of crystallization bronze corresponds to coating casting mold based on powder of zirconium dioxide (45 °C/c). The cooling rate is reduced only to 65 °C/c when coating based on aluminum oxide. Decrease the cooling rate of castings using these coatings can change the shape and size of lead inclusions and align the casting structure in section. Form inclusions lead is becoming more spherical and their interfacial surface is leveled. The greatest changes occur in the surface layers of castings. Is shown that the multicomponent bronzes decreased speed the cooling due to the use plasters leads not only to changes in the morphology of inclusions but also to lead the change in the phase composition. Decrease of cooling rate leads to increasing the amount of eutectoid and growth of hardness casting.
Authors: N.V. Martyushev, E.N. Pashkov
Abstract: In the article data about application nanopowder on a structure of coatings of the form are submitted at a casting of lead-tin bronzes. Elimination of gas porosity on a surface bronze cast preparations of high pressure compressors piston rings was the primary goal of such application protectively-dividing coverings. For experimental works mark of multicomponent bronze has been chosen. Its structure includes tin, lead, zinc and nickel. Casting from this bronze received a method of centrifugal molding. Influence of a structure of used protective - separating coating of a foundry core on a surface smoothness was probeed. Was compared action of coatings of a following composition: anti-burning-in coating (a blend of a low dispersible powder of chromium oxide with calcinated vegetable oil); anti-burning-in material ASPF-2/RgU (on the basis a low dispersible powder of graphite and the calcinated vegetable oil); the patent № 2297300 (blend of a ultradispersible powder of dioxide of zirconium with inpowderrial oil. Molding without use of coverings leads porosity depth to 4-5 mm and to a marriage significant amount (to 50 %). Use ASPF-2/RgU completely eliminates welding casting to a casting mold, but porosity on a surface remains. Application of coverings of a casting mold containing in quality of a filler ultradisperse powders oxide metals with low heat conductivity allows in to lower much a roughness and to eliminate gas porosity on a cast surface from lead-tin bronze. A gas time of a surface still remains, but them becomes much less and their form changes. Depth of defects doesn't exceed 1-1,5 mm that doesn't fall outside the limits the admission.
Authors: B. De Filippo, L. Campanella, A. Brotzu, S. Natali, D. Ferro
Abstract: In the main frame of the research aimed to model the corrosion growth on bronze surface, the objective of the work here reported has been to characterize the corrosion products formed on laboratory samples of bronze alloy (Cu Sn12), during the early stage of exposure to moist air with sulfur dioxide. A cycling corrosion cabinet was used to control 200 ppm gas concentration, relative humidity (RH) and temperature, according to the DIN 50018 (Kesternich test).The method is designed to evaluate how well the surface resists to sulfur dioxide corrosion; the test cycle consists of 8 hours exposure to sulfur dioxide at 40°C temperature and 100% relative humidity, followed by 12 hours drying at room condition. Weight variation, Spectrophotometer, Scanning Electron Microscopy with X-ray microanalysis (SEM-EDS), X-ray Diffraction (XRD) analysis were carried out for the tarnish products characterization. Some of the compound identified were brochantite (Cu4(OH)6SO4), chalcanthite (CuSO4•5H2O) cuprite (Cu2O), cassiterite (SnO2) and ottemannite (Sn2O3).
Authors: Paul S. Prevey, Douglas J. Hornbach, N. Jayaraman
Abstract: Friction stir welding (FSW) allows the joining of aluminum alloys in ways previously unattainable offering new manufacturing technology. Friction stir processing (FSP) of cast alloys such as Ni-Al bronze eliminates casting voids and improves the properties to that of wrought material. However, the local heating produced by both FSW and FSP can leave a fusion zone with reduced mechanical properties and a heat-affected zone with tensile residual stresses that can be deleterious to fatigue performance. Controlled plasticity burnishing (CPB) is an established surface treatment technology that has been investigated and described extensively for the improvement of damage tolerance, corrosion fatigue, and stress corrosion cracking performance in a variety of alloys. Mechanical CPB processing in conventional CNC machine tools or with robotic tool positioning is readily adapted to industrial FSW and FSP fabrication of components, either simultaneously or as a post process. CPB was applied to FSP Ni-Al Bronze to produce a depth of compression of 2.5 mm and a maximum subsurface magnitude of –150 ksi. The effect of FSP on the fatigue performance in a saltwater marine environment and in the presence of foreign object damage (FOD) was documented with and without CPB processing. FSP was found to increase the fatigue strength of the Ni-Al Bronze by 70% without affecting the corrosion behavior of neutral salt solution. FSW actually produced a more noble material in the acidic salt solution. CPB after FSP mitigated damage 1 mm deep.
Authors: Nikita Martyushev
Abstract: In this research it was examined the influence of crystallisation conditions binary leaded bronze on parametres of a received microstructure. Change of crystallisation conditions was carried out by change of cooling melt speed, through preliminary heating of casting moulds. Quantitative regularities of influence of cooling rate of explored bronze on parametres dendritic cells, grain size are presented. The data about formation of lead inclusions between dendrites of a copper matrix are published as well. It is shown that high rates of cooling of an order 100-150°С/c lead to dendritic structures formation containing only axes of the first and second order. Decrease of cooling rate at the moment of crystallisation to the values less 15°C/c leads to appearance and growth of axes of 3rd order at dendrites matrix.
Authors: Šárka Msallamová, Jiří Kmošek
Abstract: The study deals with a material survey and determination of the corrosion character of a Roman bronze vessel from an early Tiberian period. The ancient technology of the bronze vessel production was determined based on the evaluation of structural properties of the material using the prepared metallographic sections. The vessel was produced by combining the technologies of beating and metal embossing in a pre-cast bronze piece, side ornaments were cast from bronze. Chloride anions were identified along the material grains. It was identified that the mixture of corrosion products covering the surface of the vessel contained, in addition to other elements, basic copper chloride. The presence of chloride anions, atmospheric humidity and mechanical stress lead to corrosion of the bronze vessel called the bronze disease. The material in the upper part of the vessels lost cohesion completely and the neck of the vessel broke as a result of the corrosion process. The vessel was desalinated and reconstructed in a relatively unique way. At present, the vessel is a property of the National Museum in Prague.
Authors: D.T. McDonald, John F. Humphreys, Pete S. Bate, Ian Brough
Abstract: Copper, Cu-2%Sn and Cu-4.5%Sn alloys have been deformed in plane strain compression at temperatures up to 700oC and the evolution of the microstructures and textures determined by high resolution EBSD. The effect of the solute is to raise the temperature at which dynamic recrystallization occurs and to significantly reduce the size of the dynamically recrystallized grains. In all the materials, there is a small increase in the cube texture component on dynamic recrystallization. The boundary bulges which precede recrystallization are different in the copper and Cu-Sn alloys, although in both materials there is evidence that local deformation in the boundary regions plays a significant role in dynamic recrystallization.
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