• Advances in materials Research
• /
• v.5 no.1
• /
• pp.55-66
• /
• 2016

This paper describes a study on the effects of $Mg_2Si_{(p)}$ addition on the microstructure, porosity, and mechanical properties namely hardness and tensile properties of AA332 composite. Each composite respectively contains 5, 10, 15, and 20 wt% reinforcement particles developed by a stir-casting. The molten composite was stirred at 600 rpm and melted at $900^{\circ}C{\pm}5^{\circ}C$. The $Mg_2Si$ particles were wrapped in an aluminum foil to keep them from burning when melting. The findings revealed that the microstructure of $Mg_2Si_{(p)}/AA332$ consists of ${\alpha}$-Al, binary eutectic ($Al+Mg_2Si$), $Mg_2Si$ particles, and intermetallic compound. The intermetallic compound was identified as Fe-rich and Cu-rich, formed as polygonal or blocky, Chinese script, needle-like, and polyhendrons or "skeleton like". The porosity of $Mg_2Si_{(p)}/AA332$ composite increased from 8-10% and the density decreased from 9-12% from as-cast. Mechanical properties such as hardness increased for over 42% from as-cast and the highest UTS, elongation, and maximum Q.I were achieved in the sample of 10% $Mg_2Si$. The study concludes that combined with AA332, the amount of 10 wt% of$Mg_2Si$ is a suitable reinforcement quantity with the combination ofAA332.

• Journal of Korea Foundry Society
• /
• v.33 no.3
• /
• pp.103-112
• /
• 2013

Effect of Fe and Mn contents on the tensile properties of Al-4 wt%Mg-0.9 wt%Si alloy system has been studied. Common phases of Al-4 wt%Mg-0.9 wt%Si alloy system were ${\alpha}$-Al, $Mg_2Si$, ${\alpha}-Al_{12}(Fe,Mn)_3Si$ and ${\beta}-Al_5FeSi$. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, ${\beta}-Al_5FeSi$ compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped ${\beta}-Al_5FeSi$ compound changed to chinese script ${\alpha}-Al_{12}(Fe,Mn)_3Si$. As Fe content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Mn alloy increased from 0.15 wt% to 0.4 wt%, tensile strength of the as-cast alloy decreased from 191 MPa to 183 MPa and, elongation of the alloy also decreased from 8.0% to 6.2%. Decrease of these properties can be explained as the formation of plate shape, ${\beta}-Al_5FeSi$ phase with low Mn/Fe ratio of the alloy. However, when Mn content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Fe alloy increased from 0.3 wt% to 0.5 wt%, tensile strength of as-cast alloy increased from 181 MPa to 194 MPa and, elongation of the alloy increased from 6.8% to 7.0%. These improvements attribute to the morphology change from ${\beta}-Al_5FeSi$ phase to chinese script, ${\alpha}-Al_{15}(Fe,Mn)_3Si_2$ phase shape-modified from with high Mn/Fe ratio of the alloy.

• The Journal of Korean Medicine
• /
• v.18 no.1
• /
• pp.169-186
• /
• 1997

Scutellariae Radix has been widely used as oriental herbal medicine for the treatment of bacterial infections in the respiratory or the gastrointestinal tract. In partition experiment for better understanding of herbal medicine with various solvents, baicalein or wogonin have more hydrophobic characteristics than baicalin or wogonoside. Unexpectedly, methylene chloride could extract more for baicalin or wogonoside over other active ingredients. New compound from baicalin is discovered casting frointier area on herbal medicine in the future. Application study with new molecule hydrolyzed from baicalin is on the way for better treatment of the patient against specific disease. The baicalin modified with reaction has been shown weak antibacterial activity against Streptococcus pyogenes 308A and Pseudomonas aeruginosa 1771. The minimum inhibitory concentration (MIC) of the baicalin modified compound against those strains were about $600\;{\mu}g/mL$, respectively. In vitro antitumor experiment, $EC_{50}$ of baicalin modified with reaction was more than $300\;{\mu}g/mL$ and $EC_{50}$ of baicalein was $100\;{\mu}g/mL$. Among these compounds, baicalin exhibited high level of antitumor activity. $EC_{50}$ of baicalin was less than $33.3\;{\mu}g/mL$.

• Polymer(Korea)
• /
• v.27 no.5
• /
• pp.405-412
• /
• 2003

Poly(vinyl alcohol) (PVA) and N-(2-hydroxy)propyl-3-trimethylammonium chitosan chloride (HTCC), a water soluble chitosan derivative synthesized by the reaction of quaternary ammonium compound with chitosan, were blended using water as a solvent and the PVA/HTCC blend films with various compositions were prepared by solution casting method. The miscibility between the two polymers and the thermal properties of the blend films were investigated using FT-IR, DSC, DMA, and TGA. Single glass transition temperatures and single melting temperatures of the blend films along with the strong and clear film state for the whole composition of blending ratios suggest the miscibility between PVA and HTCC. The PVA/HTCC blend films with HTCC content of 1% and greater showed excellent antimicrobial activity.

• Journal of Korea Foundry Society
• /
• v.19 no.5
• /
• pp.403-409
• /
• 1999

Mg-Zn-Zr ternary alloys containing 6wt% Zn and (0, 0.4, 0.6)wt% Zr, which is added for grain refinement, can be cast into complex shape by squeeze casting. The influence of Zn and Zr as additional elements on microstructure and mechanical characteristics is investigated by OM, SEM, WDX, XRD and microvickers hardness measurement. The microstructure of Mg-Zn-Zr alloys consists of primary ${\alpha}-Mg$ and MgZn eutectic compound between dendrites. The grain size is decreased from $136{\mu}m$ to $97\;{\mu}m$ by Zr addition, resulting in that the hardness is increased from 42Hv to 59Hv. Furthermore, the grain size is changed to $83{\beta}$ and the hardness is increased to 65Hv by additional infiltration pressure. These results indicate that the Zr addition and additional infiltration pressure are effective for grain refinement acting as an important factor to increase the hardness. The increment in hardness by the Zr addition is slightly larger than that by the additional infiltration pressure.

• Journal of Conservation Science
• /
• v.26 no.3
• /
• pp.269-276
• /
• 2010

This study aims to extract manufacturing techniques by analysing metallurgical characteristics of the cast-iron pot from Bubjusa, examining corrosion status and microstructure with a optical microscope, SEM-EDS, micro vickers hardness tester and XRD. The microstructure analysis has presented that ferrite and partial portion of pearlite exist within the corroded outer layer. The analysis of the inner layer revealed that there is pearlite and graphite of feather shape. The one of the middle layer, which is placed between outer and inner layer, showed that corrosion has been heavily developed. Micro vickers hardness values range from 217Hv to 698Hv in constituent layers and such values lie within the ranges of the ancient iron relics. The result of EDS analysis for each microstructure presented that the outer layer has been more decarbonized than the inner layer. XRD analysis of iron corrosion compound revealed that Goethite and Hematite had been produced from the corrosive process of iron. The study concludes that the large iron pot was made by casting technique, and microstructure of inner layer had a gray cast iron. Outer layer has been decarbonized through repetitive process of heating and cooling. This results can be used as fundamental data for comparative study to reveal manufacturing techniques of large cast-iron pot.

• Journal of the Korean Vacuum Society
• /
• v.17 no.5
• /
• pp.466-472
• /
• 2008

Purple Gold is the alloy consisting of 78wt%Au-22wt%Al, and is expressed as a chemical formula, $AuAl_2$. Lately it is being used for the material of accessories or the decorative ornaments, being one of the colored golds having the peculiar purple color, like White Gold and Pink Gold. Purple Gold has the weak point in shaping through casting process due to the bad malleability and castability, being the intermetalic compound of Au and Al. Therefore, it is possible to produce the final product only by the cutting and the grinding process or to use it as a decorative coat with the thin film evaporation. This study implemented two kinds of thin film experiments. One is the case that heat treatment was made after Au and Al deposition evaporated separately with a weight ratio 78:22 on the 200nm$SiO_2$/Si substrate. The other is the case that the surface deposition was made through the vacuum evaporation, keeping the glass substrate temperature remain room temperature, using the bulk $AuAl_2$ as a source. The final film property was measured, focusing on the Purple Gold's color and thickness through the bare eye inspection, the microstructure analysis, the surface resistance analysis, the color difference analysis, and XRD analysis. Purple Gold was not formed, as the excessive surface agglomeration occurred, in case of being produced and treated thermally with 12.5nmAu/40nmAl/200nm$SiO_2$/Si structure. Our results suggest that of Purple Gold films, showing the same purple color as the bulk's, were successfully deposited with the direct thermal evaporation from the $AuAl_2$ bulk source.

• Transactions of Materials Processing
• /
• v.19 no.5
• /
• pp.311-319
• /
• 2010

Rare earth metal Ce has a relatively low melting point and high specific gravity. Because of its significantly high affinity to oxygen, nitrogen and sulfur, it is highly usable as a steel refining agent. However, because Ce compound has relatively high specific gravity, it is difficult to be separated from molten steel through floatation, and it degrades the purity of molten steel, or may clog the nozzle in continuous casting. Such problem may be solved by using an appropriate deoxidation agent together with Ce and settling molten steel sufficiently after refining. Thus a fundamental study in the formation behavior of non-metallic inclusion in Ce added Hyper Duplex STS melts was investigated. The addition amount of Ce, melt temperature were considered as experimental variables. A main non-metallic inclusion in mother alloy is 51(wt%MnO) - 27.6(wt%SiO$_2$)- 10.9(wt%$Cr_2O_3$). Non-metallic inclusion was dramatically decreased and the particle size was fined as the amount of Ce increased. Moreover (%MnO) and (%SiO$_2$) of non-metallic inclusion were decreased. But (%$Al_2O_3$)were relatively increased. The number of non-metallic inclusion were decreased and the large particle size were increased by increasing the temperature of molten steel.

• Journal of Korea Foundry Society
• /
• v.23 no.1
• /
• pp.30-39
• /
• 2003

Porous hybrid preforms were fabricated by reactive sintering using the compacts consisting of SiC particles, Fe and Al powders. Squeeze casting processing was employed to produce the composite in which the matrix phase is Al-Si7Mg. The microstructural change and wear resistance of the composites were investigated in terms of an amount of SiC particles. The wear loss was increased with increasing the contact pressure in the alloy containing SiC particles coated with Cu. The most drastic change was found to the specimen tested at 2.5 MPa of contact pressure. Concerning the alloys containing SiC particles coated with Ni-P, a drastic increase in the wear loss exhibited at 2 MPa of contact pressure in those alloys containing 4 and 8 wt. % of SiC particles coated with Ni-P. In the alloy containing 16 wt. % a proportional increase in wear loss was observed to the change of contact pressure. With respecting to the sliding velocity, the wear loss of the alloy containing SiC particles coated with Cu increased at the initial stage of wear process and then decreased. Similar result was found in the alloys containing SiC particles coated with Ni-P. On the basis of the present results obtained, it was found that wear resistance of the alloys tested was improved to show in the order of the alloy reinforced by coated SiC particles > by uncoated SiC particles > by intermetallic compound without SiC particles.

• Korean Journal of Metals and Materials
• /
• v.47 no.8
• /
• pp.488-493
• /
• 2009

Direct syntheses of bulk $Ti_3Al$ via electro-discharge-sintering (EDS) of a stoichiometric elemental powder mixture were investigated. A capacitor bank of $450{\mu}F$ was charged with three input energies, 0.5, 1.0, and 1.5 kJ. The charged capacitor bank was then instantaneously discharged through 0.3 g of a Ti-25.0 at.%Al powder mixture for consolidation. Complete phase transformation occurred in less than $200{\mu}sec$ by the discharge and a bulk $Ti_3Al$ compact was obtained. Compared with consolidated samples fabricated by conventional methods such as high vacuum sintering and casting, the electro-discharge-sintered $Ti_3Al$ compact shows a very fine microstructure with a hardness value of 425 Hv. Electro-discharge-sintering under a $N_2$ atmosphere successfully modified the surface Ti oxide of the $Ti_3Al$ compact into Ti nitride, which concurred with the synthesis and consolidation of $Ti_3Al$. Complete conversion yielding a single phase $Ti_3Al$ is primarily dominated by the fast solid state diffusion reaction.