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[en] An innovative spray-deposition technique has been applied to produce in situ TiC/Al and TiC/Al-20Si-5Fe-3Cu-1Mg composites. This technique provides a new route to solve the problems of losses and agglomeration of the reinforcement particles when they are injected into the spray cone of molten droplets during spray forming process. Experimental results have shown that the presence of needle-like Al₃Ti and Al-Si-Fe compounds, which are detrimental not only to the fracture toughness, but also to the stability of the microstructure, can be eliminated completely from the final product by using a proper Ti:C molar ratio of 1:1.3 in the Ti-C-Al preforms and adding 5 wt% TiC particles to Al-20Si-5Fe-3Cu-1Mg alloy. Moreover, another major problem of coarsening of silicon particles usually encountered in the hypereutectic Al-Si alloys has also been solved by the technique. The silicon particles in the spray-deposited 5 wt% TiC/Al-20Si-5Fe-3Cu-1Mg composite were much refined (∼2 μm) compared to those (∼5 μm) obtained in the matrix alloy without TiC addition. The formation and elimination mechanisms of Al₃Ti phase in TiC/Al composites can be explained based on thermodynamic theory. The modification of the microstructures in the spray-deposited Al-20Si-5Fe-3Cu-1Mg alloy can be interpreted in the light of the knowledge of atomic diffusion. The experimental results also showed that the ultimate tensile strength of the TiC/Al composites was improved over that of the unreinforced Al matrix

[en] Highlights: • Thermal response for brick filled with PCMs can be divided into three periods. • Temperature control times for brick with PCMs are 2.5 times than that without PCMs. • Temperature uniformity of aluminum base is better in latent heat period. • Holes closer to the bottom of sample behave the stronger natural convection. -- Abstract: Based on the thermal management requirements of bearing structures in the thermal protection system of aircrafts, a group of aluminium hollowed bricks with low porosity is manufactured. The thermal response characteristics of these bricks filled with 48.3–57.8 °C paraffin are experimentally studied. The results show that the infilling of PCMs may significantly retard the heat transfer through the bricks due to the large latent heat absorption, and the temperature control time is thus 2.5 times that for the case without PCMs. The samples with higher porosity have longer melting duration times and lower entire temperatures after completely melting. A higher porosity or larger hole diameter is more beneficial for the thermal control at the cold end because of the lower effective thermal diffusivity. A numerical model is also established to further analyse the field distributions of the samples. The simulation shows that the natural convection of the liquid PCMs in holes is a laminar flow. In contrast to the sensible heat period, the temperature uniformity of the aluminium base is better in the latent heat period, and the corresponding temperature fluctuation amplitudes along the centre-lines of the holes are larger. Furthermore, whether for bottom heating or top heating, the holes that are closer to the bottom of the sample have stronger natural convection. These findings can provide beneficial guidance for the design of a thermal control system with metallic hollowed geometries.

[en] Corrosion of the reduction vessel induced by molten LiCl-Li₂O is an important problem in the lithium reduction technique for the spent nuclear fuel management. This study investigates the corrosion of nickel in molten LiCl-10 wt% Li₂O at 750 deg. C by immersion experiments, with the aim of unraveling the corrosion behavior. Nickel corrodes very fast in the melt, forming a layer of NiO, which is converted to Li₂Ni₈O₁₀ and then to LiNiO₂. The weight loss curve shows a linear rate law, which is owing to the harmful reaction between oxides and melt at the melt/scale boundary with the formation of the porous corrosion scale. The corrosion mechanism of nickel is also discussed

[en] Sb-substituted Nd₂Fe_17-xSb_x and Sm₂Fe_17-xSb_x materials were synthesized using a modified reduction-diffusion process with superfine Fe metal powder as starting material. Sb is a volatile element at high temperature and Sb-substituted intermetallic materials cannot be prepared using a conventional metallurgical method. The substitution of Sb in Nd₂Fe₁₇ and Sm₂Fe₁₇ enhances significantly the magnetic interaction between Fe atoms and improves their chemical stability, particularly for Sm₂Fe₁₇-related materials. (orig.)

[en] At Korea Atomic Energy Research Institute (KAERI), we investigated the corrosion behavior of a series of Fe-Cr-Ni alloys with different chromium contents in molten LiCl and molten LiCl-25wt%Li₂O mixture at temperatures ranging from 923 to 1123 K. In molten LiCl, dense protective scale of LiCrO₂ grows outwardly while corrosion is accelerated by addition of Li₂O to LiCl. The basic fluxing of Cr₂O₃ by Li₂O would be the cause of accelerated corrosion. Because of low oxygen solubility and very high Li₂O activity in the molten LiCl-Li₂O mixture, Cr is preferentially corroded while Ni remains stable and thus, corrosion rate of the alloys in molten LiCl-Li₂O mixture increases with an increase in Cr content

[en] The non-isothermal precipitation behaviors of Al–Mg–Si–Cu alloys with different Zn contents were investigated by differential scanning calorimetry (DSC) analysis, hardness measurement and high resolution transmission electron microscope characterization. The results show that Zn addition has a significant effect on the GP zone dissolution and precipitation of Al-Mg-Si-Cu alloys. And their activation energies change with the changes of Zn content and aging conditions. Precipitation kinetics can be improved by adding 0.5 wt% or 3.0 wt%Zn, while be suppressed after adding 1.5 wt%Zn. The Mg-Si precipitates (GP zones and β″) are still the main precipitates in the Al-Mg-Si-Cu alloys after heated up to 250 °C, and no Mg-Zn precipitates are observed in the Zn-added alloy due to the occurrence of Mg-Zn precipitates reversion. The measured age-hardening responses of the alloys are corresponding to the predicted results by the established precipitation kinetic equations. Additionally, a double-hump phenomenon of hardness appears in the artificial aging of pre-aged alloy with 3.0 wt% Zn addition, which resulted from the formation of pre-β″ and β″ precipitates. Finally, the precipitation mechanism of Al-Mg-Si-Cu alloys with different Zn contents was proposed based on the microstructure evolution and interaction forces between Mg, Si and Zn atoms.