1,721,048 research outputs found
Ferritic Stainless Steels for High Temperature Applications in Oxidizing Environments
No full textFerritic stainless steel containing more than 7 wt. % of Al represents an interesting material for the production of components working at high temperature. To meet industrial needs of increased operating temperatures, many studies have been carried out to design FeCrAl(RE) alloys that are suitable for applications where the components have to work in oxidative environments for extended periods of operation, often at very high temperatures (>1000 °C) under cyclic operating conditions. Although a very good protectiveness against oxidation can be achieved for Al concentrations higher than 7 wt.%, mechanical properties of FeCrAl alloys are known to be poor at high temperature. High temperature strength and creep resistance can be improved by reducing grain boundary areas and by precipitating stable particles in the bulk alloy: this practice prevents grain boundary slip and dislocation movement. This paper reviews the patented progresses in the field of the production of FeCrAl alloys for high temperature applications such as heating elements and substrate of catalytic converters. © 2009 Bentham Science Publishers Ltd
Studio su scala pilota di laboratorio per la realizzazione di un processo idrometallurgico di trattamento delle polveri EAF
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Cold roll bonding and annealing process to produce an intermetallic layer on Ti substrate
No full textTitanium is characterized by poor resistance against oxidation at high temperature. Surface modification by formation of titanium aluminide coatings would be effective to improve oxidation resistance. In this study, a 100 μm aluminum foil was initially bonded with a 1 mm Ti sheet by means of cold roll bonding. The aluminum clad Ti foil was heat treated over the temperature range 600-1000°C in order to form an outer TiAl3 layer protecting the substrate from high temperature oxidation. Al and Ti concentration profiles, as well as microhardness profiles, were determined in order to investigate the relationship between heat treatment conditions and formation of intermetallic compounds. The morphology and the structure of TiAl3 layer formed at different temperatures were studied by means of SEM/EDS and X-ray diffraction
Reductive stripping in vacuum of Fe(III) from D2EHPA
No full textThe iron stripping from di(-2-ethylhexyl)phosphoric acid (D2EHPA) constitutes a problem in hydrometallurgical processes: whereas Fe(III) is easily extracted along with other elements such as zinc or cadmium, it is hard to strip it from the organic phase. It is well known that Fe(II) is readily stripped from D2EHPA, so a reduction of ferric to ferrous iron could be a way to solve this problem. In this work, the reductive stripping in vacuum of Fe(III) from D2EHPA has been studied by using SHG zinc powder as a reducing agent. The optimisation of operating conditions, such as degree of vacuum, acid concentration and quantity of added zinc, has been made. The experiments showed that a stripping yield greater than 89% in only one stage can be achieved, depending on A/O ratio, at 80 kPa of pressure. The iron reduction and stripping have been done simultaneously. (C) 2000 Elsevier Science B.V. Ail rights reserved
Effect of wall microstructure and morphometric parameters on the crush behaviour of Al alloy foams
Full text linkThree different aluminium foams, manufactured by compact powder technology starting from 7075, 6061 and AlSi7 alloys were studied by performing microstructural and morphometric analyses, with the aim of explaining their different behaviour during axial crushing. Void distribution coupled with material microstructure justifies the behaviour of load-displacement curves obtained during axial crushing of the foams. The results show that 7075 alloy seems to be the material having the best behaviour during crushing, at least when the foam is removed of the external walls. Despite that outer skin presence coupled with the intrinsic brittle behaviour of this alloy may cause instability, if it is used to fill hollow components like crashboxes. During deformation process 6061 and AlSi7 alloys that are more ductile, give in and maintain contact adapting to the encasement deformation. (c) 2007 Elsevier B.V. All rights reserved
Electrodeposition of nickel-cobalt alloys from sulfate acid baths
No full textIn this work, nickel-cobalt electrodeposition under galvanostatic conditions was investigated. Ni-Co alloy was electrowon from an acid sulphate bath containing 40 g/L Ni and 2-8 g/L Co. The effect of electrolyte composition, current density, temperature, solution pH and presence of buffers such as H3BO3 and (NH4)(2)SO4 on Co content of the binary alloy has been investigated. In particular, current densities ranging from 180 to 400 A/m(2) and temperatures ranging from 27 to 60degreesC were tested. The composition of Ni-Co alloys may be diversified through the selection of process parameters. The experiments show that the highest cobalt content of the alloy is reached by using a buffer free electrolyte without solution pH control. Though, in these conditions, the most homogeneous, fine and regular deposit morphology is obtained, energy requirements are the highest in tests lasting just two hours
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