• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.356-364
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• 1997

In order to study effects of Cu and Be on the microstructure and tensile properties of rapidly solidified Al-Mg alloys, Al-Mg-Cu-Be alloys have been rapidly solidified by inert gas atomization process. Microstructure of rapidly solidified Al-Mg-Cu-Be powders exhibited refinement and good dispersion of Be particles as increasing of solidification rate. Solidification rate of atomized powders was estimated to be about $5{\times}10^{3{\circ}}C/s$. Inert gas atomized Al-Mg-Cu-Be powders were hot-processed by vacuum hot pressing at $450^{\circ}C$ under 100 MPa and hot extruded with reduction ratio in area of 25: 1 at $450^{\circ}C$. The extruded Al-Mg-Cu-Be powders consisted of recrystallized fine Al grains and homogeneously dispersed fine Be particles, and exhibited improved tensile properties with increase in Cu content. $Al_2CuMg$ compounds precipitated in grain and grain boundaries of Al-Mg-Cu-Be alloys with aging heat treatment after solution treatment. Hardness and tensile properties were improved by increasing Cu content and Be addition. Compared with extruded Al-Mg-Cu powders, the extruded Al-Mg-Cu-Be powders exhibited finer recrystallized grains and improved tensile properties by dispersion hardening of Be and subgrain boundaries pinned by fine Be particles. After aging treatment, hardness and tensile properties were improved due to restricted precipitation by increasing of dislocation density around Be particles in matrix.

• Metals and materials international
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• v.24 no.6
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• pp.1394-1402
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• 2018

This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.

• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.634-645
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• 2008

In this study, surface composites were fabricated with Fe-based amorphous alloy powders and VC powders by high-energy electron beam irradiation, and the correlation of their microstructure with hardness and fracture toughness was investigated. Mixture of Fe-based metamorphic powders and VC powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders without flux to fabricate surface composites. The composite layers of 1.3~1.8 mm in thickness were homogeneously formed without defects and contained a large amount (up to 47 vol.%) of hard $Cr_2B$ and $V_8C_7$ crystalline particles precipitated in the solidification cell region and austenite matrix, respectively. The hardness of the surface composites was directly influenced by hard $Cr_2B$ and $V_8C_7$ particles, and thus was about 2 to 4 times greater than that of the steel substrate. Observation of the microfracture process and measurement of fracture toughness of the surface composites indicated that the fracture toughness increased with increasing additional volume fraction of $V_8C_7$ particles because $V_8C_7$ particles effectively played a role in blocking the crack propagation along the solidification cell region heavily populated with $Cr_2B$ particles. Particularly in the surface composite fabricated with Fe-based metamorphic powders and 30 % of VC powders, the hardness and fracture toughness were twice higher than those of the surface composite fabricated without mixing of VC powders.

• Journal of Korea Foundry Society
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• v.43 no.4
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• pp.187-193
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• 2023

Shell core making is an excellent process in terms of formability and desanding, but when the molten aluminum comes into con- tact with the shell core, gas generation by pyrolysis of the resin is inevitable. In addition, when the ventilation is inadequate, pores will remain inside the casting, which can directly lead to defects of the casting. While studies on the gas generation behavior of shell core making have been reported, the modeling of gas generation has not been extensively investigated. We will develop a gas evolution analysis method that considers the relationship between temperature and gas quantity for the core to be developed. We then use the developed method to analyze the flow and solidification behavior of metal molten metal during core mold design and low-pressure casting of cylinder head products, and predict the occurrence of casting defects to derive a casting method that min- imizes the occurrence of defects.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.59-65
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• 2012

Solidification/Stabilization(S/S) is one of the remediation technologies that have been applied for treating inorganic hazardous wastes. This study investigated the reduction of arsenic concentration of arsenic-contaminated soil using by S/S. The binder plays a role in controlling the mobility and solubility of the contaminants in S/S process, so it is important to determine the optimum binder content. Therefore, this study evaluated the effectiveness of S/S using four different binders(cement, zero valent iron, and monosulfate and ettringite(cement-based synthesized materials) at the binder content ranged between 5%(wt.) and 20%(wt.). The leachability of arsenic in 1 N HCl was different depending on the types of binders: cement(71.41%) > monosulfate(47.45%) > ettringite(46.36%) > ZVI(33.08%) at the binder content of 20%. Additionally, three kinds of a mixture binder were prepared using cement and additives(monosulfate, ettringite, calcium sulfoaluminate(CSA)) and tested for arsenic reduction. The highest arsenic removal capacity was found at the mass ratio of cement to the additive, 4:1 in all experiments using a mixture binder, regardless of the additives types. A mixture binder(cement and additives) resulted in higher arsenic removal relative to the arsenic removal when cement was used alone.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.27-40
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• 2014

So far, studies on the settlement of breakwater have mainly been conducted through numerical model tests focusing on an analysis or through the laboratory wave tank tests using a scaled model. There has not been a study on the settlement that is measured in an actual breakwater structure. This study analyzed the data of settlement that has been measured in an actual caisson breakwater for a long time and the characteristics and causes of wave-induced settlement in the caisson (including beneath ground), based on qualitative aspect, were examined. The analysis revealed that wave clearly has an effect on the settlement in caisson, especially in the condition of high wave such as typhoon. Caisson settlement is caused by the liquefaction of ground, which is due to the increase of excess pore pressure, the combination of oscillatory excess pore pressure and residual excess pore water pressure, and the solidification process of ground due to dissipation of the accumulated excess pore pressure. The behavior of excess pore pressure in the ground beneath the caisson is entirely governed by the behavior of the caisson. Ground that has gone through solidification is not likely to go through liquefaction in a similar or a smaller wave condition and consequently, the possibility of settlement is reduced.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.213-213
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• 2000

This study was performed to investigate types and formation mechanism of cracks in two Al alloy welds, A5083 and A7NO1 spot-welded by pulse Nd: YAG laser, using SEM, EPMA and Micro-XRD. In the weld zone, three types of crack were observed: center line crack($C_{C}$), diagonal crack($C_{D}$), and U shape crack($C_{U}$). Also, HAZ crack($C_{H}$), was observed in the HAZ region, furthermore, mixing crack($C_{M}$), consisting of diagonal crack and HAZ crack was observed.White film was formed at the hot crack region in the fractured surface after it was immersed to 10%NaOH water. In the case of A5083 alloy, white films in C crack and $C_D crack region were composed of low melting phases, Fe₂Si$Al_8$ and eutectic phases, Mg₂Al₃ and Mg₂Si. Such films observed near HAZ crack were also consist of eutectic Mg₂Al₃. In the case of A7N01 alloy, eutectic phases of CuAl₂, $Mg_{32}$ (Al,Zn) ₃, MgZn₂, Al₂CuMg and Mg₂Si were observed in the whitely etched films near $C_{C}$ crack and $C_{D}$ crack regions. The formation of liquid films was due to the segregation of Mg, Si, Fe in the case of A5083 alloy and Zn, Mg, Cu, Si in the case of A7N01 aooly, respectively.The $C_{D}$ and $C_{C}$ cracks were regarded as a result of the occurrence of tensile strain during the welding process. The formation of $C_{M}$ crack is likely to be due to the presence of liquid film at the grain boundary near the fusion line in the base metal as well as in the weld fusion zone during solidification. The $C_{U}$ crack is considered a result of the collapsed keyhole through incomplete closure during rapid solidification. (Received October 7, 1999)

• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.30-33
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• 2002

The Effects of Co-substitution in the nanocrystalline Nd-Fe-B-Mo-Cu alloys were investigated. $\alpha$-Fe based nanocrystalline Nd-Fe-B-Mo-Cu alloys were prepared by crystallization process of amorphous Nd-Fe-B-Mo-Cu alloy produced by rapid solidification process. The substitution of Co resulted in the decrease of grain size and improves the hard magnetic properties. The remanence, coercivity, and Curie temperature of nanocrystalline N $d_4$(F $e_{0.85}$ $Co_{0.15}$)$_{82}$ $B_{10}$M $o_3$Cu alloy showed more improved magnetic properties than those of Co-free alloy. The grain size was measured to be about 15 nm. The coercivity, remanence and maximum energy product were 239 kA/m, 1.41, and 103.5 kJ/ $m^3$, respectively, for the nanocrystalline N $d_4$(F $e_{0.85}$ $Co_{0.15}$)$_{82}$ $B_{10}$M $o_3$Cu alloy annealed for 0.6 ks at 640 $^{\circ}C$.

• Resources Recycling
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• v.20 no.3
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• pp.28-39
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• 2011

This review investigated theoretical principals and practical application examples on recirculation system of soil washing-wastewater treatment-treated water recycling. As for technologies which have attempted to remediating metals-contaminated soil in and around country, there are reactive barriers, encapsulation, solidification/stabilization, soil washing, and phytoremediation. Among those, in particular, this review covers soil washing technology which physicochemically removes contaminants from soils. The major drawbacks of this technology are to generate a large amount of wastewater which contains contaminants complexed with ligands of washing solution and needs additional treatment process. To solve these problems, many chemical treatment methods have been developed as follows: precipitation/coprecipitation, membrane filtration, adsorption treatment, ion exchange, and electrokinetic treatment. In the last part of the review, recent research and field application cases on soil washing wastewater treatment and recycling were introduced. Based on these integrated technologies, it could be achieved to solve the problem of soil washing wastewater and to enhance cost effective process by reducing total water resources use in soil washing process.

• Journal of Animal Environmental Science
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• v.15 no.2
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• pp.155-160
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• 2009

This study was carried out to investigate the feasibility of Multi Process of Aerobic Digestion (MPAD) for recycling of swine manure slurry as fertilizer. MPAD consisted of three kinds of difference process which are thermophilic aerobic oxidation (TAO) system, lime solidification system, and reverse osmosis (R/O) membrane system. TAO system was studied well previously for decade. The chemical composition of the lime-treated solid fertilizer was as like that organic matter 17.4%, moisture 34.1%, N 0.9%, P 1.7%, K 0.3%, Ca 12.7%, and which was expected to be useful as acid soil amendment material. The concentrated liquid material produced by R/O membrane system was also expected as a good fertilizer for crops production and soil fertility improvement.