查看更多>>摘要：Abstract In general, many cast parts require a final surface finish which could be sand blasting, grinding, or machining. In such applications, the cutting tool life is a critical parameter where the mass production rate becomes important. Therefore, in this work, the correlation between melt quality and machinability of the high-pressure die-cast Al9Si3Cu alloy was investigated. Prior to casting, reduced pressure test samples were collected to quantify the melt cleanliness by means of bifilm index. The tool life was measured based on the fracture of the PCD (polycrystalline diamond) cutting tools. It was found that, when the bifilm index was high (i.e., bad quality), 16 cutting tools were used for the machining of 10,000 parts. On the other hand, when the bifilm index was low (good quality melt), only 4 tools were used for 12,000 machined parts.
查看更多>>摘要：Abstract How to obtain an efficient dealkalization process is a key issue for the resource treatment process of red mud. In this work, CaO was added to red mud and then mixed by ball milling after the mixture had been microwave roasted and water leached to achieve efficient dealkalization. The comparative investigation between the conventional roasting and microwave roasting-water leaching process was conducted. After that, the main factors and the mechanism of dealkalization of red mud under microwave roasting conditions were discussed. The results show that microwave roasting has better dealkalization efficiency and less energy consumption than conventional roasting under the same conditions. The dealkalization rate arrived at 84.04% under the optimum conditions, i.e., CaO/SiO2 molar ratio 2.4, microwave power 2.5 kW, roasting temperature 500°C, roasting time 45 min, liquid-solid ratio 8 mL/g, leaching temperature 90°C and leaching time 80 min. Ball milling promoted the mixing degree of red mud and CaO. The microwave roasting could effectively improve the crystal phase transformation of the alkali component in the red mud throughout the roasting process. The alkali metal component in the red mud was significantly extracted. The research can provide an idea for dealkalization and resource utilization of red mud.
查看更多>>摘要：Abstract Red mud based ceramic tiles were successfully fabricated by high-temperature sintering and the influence of the Fe2O3 content on their comprehensive performance, mineral phase, and microstructure were systematically investigated. The results indicate that iron is involved in the structural reorganization of mullite during the nucleating process. Adding 9% Fe2O3 elongated mullite crystals to an aspect ratio of 15.6 ± 2.1, and the crystals were successfully obtained at a sintering temperature of 1300°C for 2 h. In this case, the values for water absorption and compressive strength of the red mud based ceramics were 6.6% and 178.3 MPa, respectively, reaching the national standard for building materials. Putting the right amount of Fe2O3 into ceramics can not only promote the anisotropic growth of mullite crystals but can result in the formation of an interlocked network of mullite at lower temperatures. This work will contribute to a better understanding of the influence of Fe2O3 on basic material performance, such as structural, micro-analysis, and mechanical characteristics of ceramic tiles with iron-containing mullites.
查看更多>>摘要：Abstract A NH4HSO4 roasting and water leaching process has been proposed to efficiently extract aluminum from secondary aluminum dross (SAD). The aluminum was recovered in the form of?Al(OH)3 after precipitation by adjusting the PH of the leaching liquid. Al2O3 was prepared by roasting the Al(OH)3. The effects of the extracting behaviors of aluminum under different processing conditions were systematically studied. SEM, XRD, FT-IR, and TG/DTA have been used to elucidate the phase evolution during the whole process. After the NH4HSO4 roasting and water leaching, 94.9% of the aluminum was extracted with a m(NH4HSO4)/m(Al) mass ratio of 7, roasted at 400°C, and maintained for 90?min. Optimal leaching conditions were a leaching temperature of 90°C, a ratio of liquid to solid (L/S:g/g) of 10 and a leaching time of 80 min. During roasting, the NH4HSO4 reacted with the aluminum and formed NH4Al(SO4)2 dissolved in water, and 98.4% of the aluminum was precipitated from the leaching liquid by adjusting the pH value of 6.0, a precipitation time of 120?min, and a precipitation temperature of 60°C. The purity of the Al2O3 was 98. 8% by roasting Al(OH)3 at 1200°C.
查看更多>>摘要：Abstract A novel hybrid manufacturing technique combining friction stir welding and spinning provides a promising approach to forming large-diameter thin-walled axisymmetric components while minimizing process scrap. By integrating experimental and numerical methods, the feasibility of the hybrid manufacturing technique for producing thin-walled axisymmetric components with the 2195 Al-Li alloy was explored. The results indicate that the welding seam of the spun components restricts plastic deformation, which leads to flange swing. The movement of the welding seam occurs during spinning, and the movement direction is consistent with the rotation direction of the spun components. The microhardness of the components in the welding zone was found to increase by 21% on average after spinning. Moreover, the yield strength in the welding zone increased by over 60% and the tensile strength by over 12%. These results suggest that the hybrid manufacturing technique is a feasible way to produce large-diameter thin-walled axisymmetric components. Since the process scraps can be re-utilized using this method, it thus provides a potential route for sustainability in the recycling and remanufacturing of aluminum alloys.
Aune Ragnhild ElizabethClos Daniel PerezZedel HannesJohnsen Sverre Gullikstad...
12页
查看更多>>摘要：Abstract Hard grey scale (HGS) is a strongly adhering fouling material forming on solid surfaces impinged by off-gas generated in the pot cells of primary aluminium production plants. Even though associated maintenance costs have a significant economic impact, the mechanisms behind HGS formation are not well understood. In the present work, a cooled fouling probe or “cold finger” placed in the off-gas duct, upstream of the gas treatment centre (GTC), at a Norwegian aluminium production site was used to study the formation mechanisms of HGS. Fouling experiments were performed with durations ranging from a few hours to several months. HGS formed on the windward side of the probe, whereas dusty and loosely attached deposits accumulated on the leeward side. The chemical composition and crystal phase evolution of the different deposits and off-gas particle samples were analysed by electron probe micro-analyser equipped with an energy-dispersive spectrometer (EPMA-EDS), quantitative x-ray diffraction (Q-XRD), LECO-C and transmission electron microscopy (TEM). Moreover, image analysis (IA) was used to investigate the particle size distribution and deposition properties of particles with different compositions. Inertial deposition of atmolite (NaAlF4) nanoparticles, produced by pot cell electrolyte vapour condensation, has been identified as the key mechanism in the formation of HGS.
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Springer Nature