Papers by Keyword: Recovery

Abstract: Industrial wastes contribute significantly to environmental pollution following the directives of European environmental policies, we must look for alternatives for minimization, treatment and / or recovery of wastes [1]. Several studies have found that basic materials such as polymers, cements and ceramics are better suited to inerting and neutralization of the waste by encapsulation in your matrix [2]. They are also increasingly used more insulating bricks. One way to increase this capacity is introduce additives organics into the matrix [3]. This is the case presented below, where they have used sludge from water purification of the brewing industry for the manufacture of ceramics.

Abstract: Industrial residues generated by the modern society constitute an environmental problem and are harmful both to the health and to the environment (greenhouse effect). In addition, they can give place to leaching pollutants [1,2] more concretely in the European area; it tends to the politics of them 3R, recovery, recycling and reutilization. It is, in this frame, where the present work is included. On the other hand, like result of environmental regulations, bricks of clay are going to be demanded by an increase in the insulating capacity. A way of increasing the insulating capacity of the bricks is to generate porosity in the counterfoil of clay.

Abstract: In shape memory alloys (SMA), the texture can be an interesting factor influencing the anisotropic physical and mechanical characteristics during the phase transformations. It is well known that the texture significantly influences the stress-strain curve and shape memory strain of NiTi SMA. The aim of the present experiment was to analyze the textural modifications in the Ti-rich Ni-Ti SMA after annealing at moderate (500°C for 30 min) and subsequent low level of cold work reduction (10% thickness reduction). The textural results were obtained by X-Ray Diffraction (XRD) during thermal cycling in three points: (i) at room temperature (B19’ phase, after cold work), (ii) at 180°C (B2 phase), and (iii) at room temperature (B19’ phase, after cooling from 180°C). The phase transformations were characterized by Differential Scanning Calorimetry (DSC) and XRD.

Abstract: The investigated super duplex steel belongs to the group of stainless steels which exhibits an austenitic-ferritic microstructure with a phase fraction of about 50% austenite and 50% ferrite. The alloy shows excellent general corrosion resistance as well as a good resistance against stress corrosion cracking, corrosion fatigue and erosion corrosion. Due to these outstanding properties, the super duplex alloy is used in components for sea or waste water applications and in the offshore and chemical industry. In addition, the investigated super duplex steel exhibits a good weldability and a high strength in comparison to pure austenitic steel grades In order to optimize the production process and to provide a suitable microstructure to satisfy the customer’s requirements multiaxial forging test at various temperatures were performed in the Gleeble Maxstrain system. The force and the displacement after each anvil stroke were measured and used to distinguish the mechanical behaviour in the forging process at different thermal conditions. The recorded force and displacement is also compared with a multi step compression test to show the influence of change in the deformation direction. A certain number of samples were exposed an in-situ heat treatment after the deformation while other samples were immediately quenched after the forging to preserve the deformed microstructure, which was measured by optical microscopy and electron microscopy. Furthermore, electron back scatter diffractions scans were applied to characterize the degree of dynamic recrystallization during the forging process.

Abstract: New thermo-mechanical processes (TMPs) to produce ultrafine-grained copper alloys utilizing continuous recrystallization (cRX) were proposed. These methods stand on our hypothesis that the evolution of ultrafine grains can be evolved by a mechanism of cRX even during severe plastic deformation at ambient temperature. A TMP of warm compression of 10 to 20 % of Cu-1.7mass%Fe alloy followed by annealing was cyclically repeated. The slight reduction, low-temperature annealing and pinning of grain boundaries by precipitates efficiently impeded occurrence of discontinuous recrystallization (dRX). The evolved substructures with nodes of the Fe precipitates gradually changed to new grains surrounded by low- and high-angle boundaries with increasing number of the repeated processes. Ultrafine grains with average size of 0.7 m were successfully evolved. However, the onset of dRX triggered extended grain coarsening accompanied by grain-boundary migration under conditions of insufficient annealing temperature and large pass stain. Another TMP cycles of cold rolling and annealing also induced fine-grained structure of about 0.6 m. The above results improved that ultrafine grain refinement can be realized simply by a mechanism of cRX even in the metallic materials with low stacking fault energy.

Abstract: The structural recrystallization mechanisms operating in an Fe – 27%Cr – 9% Ni dual-phase (ferrite-austenite) stainless steel after large strain processing to total strain of 4.4 were investigated in the temperature range of 400-700oC. The severe deformation resulted in the development of an ultrafine grained microstructure consisting of highly elongated grains/subgrains with transverse dimensions of 160 nm and 130 nm in ferrite and austenite, respectively. The annealing mechanism operating in ferrite phase was considered as continuous recrystallization, which involved recovery leading to the development of essentially polygonized microstructure. On the other hand, the mechanism of discontinuous nucleation took place at an early recrystallization stage in austenite phase.

Abstract: Forged and extruded TiAl products suffer from structural and chemical inhomogeneities that reduce the reliability of components. In an attempt to improve the homogeneity of the material, the feasibility of cyclic axial deformation and cyclic torsional deformation superimposed with compression, where much higher strains can be imparted into the material than during forging and extrusion, were investigated. Accordingly, during torsion superimposed with compression pronounced shear localization and cracking occurs. These difficulties can largely be overcome by cyclic axial deformation.

Abstract: The effects of strain, annealing time and temperature during the processing of an Al-Sn-based triboalloy were researched by response surface analysis. A second-degree polynomial in strain-time-temperature space was compared to a formulation based on generally accepted physical models for recrystallisation, recovery and grain growth, using the rule of mixtures for a microstructure consisting of recovered, recrystallised and second-phase grains. The polynomial approach provides interesting information on the role of rolling reduction in the optimisation of the alloy. The mechanism-based approach yields higher precision with less fitting parameters and provides insight into the relative importance of the physical phenomena involved in the processing of an alloy which has rarely been studied from the viewpoint of physical metallurgy.

Abstract: The run-of-mine of complex lead-zinc ores in Yunnan contains 3.26% lead and 2.54% zinc. When traditional selective flotation flowsheet was adopted, 3.77% yield and 61.92% grade of lead concentrate as well as 5.65% yield and 38.67% grade of zinc concentrate were achieved. Simultaneously, 72.39％ lead recovery and 3.83% zinc grade in lead concentrate as well as 80.64% zinc recovery and 6.39% lead grade in zinc concentrate were obtained. Lead concentrate and zinc concentrate obtained from selective flotation contain each other severely, resulting in low recovery of lead and zinc and severe loss of metal, which influences subsequent smelting flowsheet. In addition, due to requirement of large amount of depressant and activator while separating lead and zinc in the process of mineral processing, the cost is very high and the compositions of tail water which can not be recycled by the plant are very complicated. For the combined flowsheet of beneficiation and metallurgy, bulk flotation flowsheet was adopted. Therefore, 11.22% yield of combined lead and zinc concentrate with 25.55% lead grade, 18.33% zinc grade and 86.36% lead recovery were obtained. Gravity separation technology was utilized to separate combined concentrate of lead and zinc. After selecting out part of high quality lead concentrate, the remaining combined concentrate of lead and zinc was treated by acid leaching under high pressure. The final leaching efficiency of zinc was able to reach 97%. The new combined flowsheet has lots of advantages such as shorter flowsheet of beneficiation, simpler reagents, more direct reuse of backwater and higher recovery of metals.

Abstract: The thermal stability of equal channel angular extruded VT-6(Ti-6Al-4V) has been examined using micro-hardness, nano-hardness of the individual αand β phases backscattered scanning (BSEI) and transmission electron microscopy (TEM). After straining to an equivalent total equivalent of 6.5 samples were annealed for 1 h at temperatures between 175 and 800 o C followed by water quenching. Micro and nano-hardness measurements showed an initial hardness increase, the former rising to a maximum at 175°C, while the latter exhibited a maximum at 500°C. BSEI and TEM analysis showed that these observations can be understood by considering the microstructure changes occurring at different length scales. Annealing in the temperature range of 175 to 500°C did not significantly alter the α and β particle size, while TEM showed that recovery and continuous recrystallization occurred in the α phase, higher temperatures being required to activate the recovery and recrystallization processes within the β phase. Finally at temperatures above 600°C spheroidization and growth of the β phase occurred with the volume fraction of this phase increasing from 15 pct at lower temperature to 25 pct at 800°C, an equi-axed α+ β microstructure being observed at this temperature.