• Journal of the Korean Society for Heat Treatment
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• v.11 no.2
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• pp.82-91
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• 1998

The elastic modulus and wear resistance in austempered ductile cast iron(ADI) are two important mechanical properties for automobile parts. Therefore, the effect of Cu, Ni, Mo and special austempering treatment such as preheated, prequenched, and step austempering treatments on elastic modulus and wear resistance has been investigated systomatically. As a result, elastic modulus and wear resistance were increased by the addition of Mo-Cu and preheated austempering treatment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.102-108
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• 2018

The objective of this study is to develop the mechanical properties of an AlSiCu aluminum alloy using the two-step solution heat treatment. The microstructure of the gravity casting specimen represents a typical dendrite structure with a secondary dendrite arm spacing (SDAS) of 40 um. In addition to the Al matrix, a large amount of coarsen eutectic Si phase, $Al_2Cu$ intermetallic phase, and Fe-rich phases is generated. The eutectic Si phases are fragmented and globularized with the solution heat treatment. The $Al_2Cu$ intermetallic phase is also resolutionized into the Al matrix. The $2^{nd}$ solution temperature at $525^{\circ}C$ may be an optimal condition to enhance the mechanical properties of the AlSiCu aluminum alloy.

• Transactions of Materials Processing
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• v.8 no.6
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• pp.626-633
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• 1999

$Al_{85}Ni_{10}Y_5$ (at. %) amorphous alloy ribbons have been produced by rapidly solidification process and consolidated by the conventional powder metallurgy method. The grains with ∼90 nm were obtained in the Al85Ni10Y5 alloy extrudates by hot-pressing followed by hot-extusion. To investigate the effect of heat treatment on microstructural change of the extrudates, heat treatment was carried out from 200℃ to 400℃ at the step of 50℃. In addition, mechanical properties of the extrudates were analysed from torsion test at the temperature range or 400∼500℃ under a strain rates of 0.2, 0.5, and 1.0/sec. The extrudates showed a flow stress of ∼190 MPa and low elongation of ∼150% at 400℃, contributing to the enhancement of ductility and hardness for extrudates. Also, grain boundary sliding was occurred in the $Al_{85}Ni_{10}Y_5$ alloy during hot deformation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.399-402
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• 2007

The effects of heat treatment on the electrical properties of strained-Si/SiGe-on-insulator (SGOI) devices were examined. We proposed the optimized heat treatment processes for improving the back interfacial electrical properties in SGOI-MOSFET. By applying the additional pre-RTA (rapid thermal annealing) before gate oxidation step and the post-RTA after source/drain dopant activation step, the electrical properties of strained-Si channel on $Si_{1-x}Ge_x$ layer were greatly improved, which resulting the improvement of the driving current, transconductance, and leakage current of SGOI-MOSFET.

• Macromolecular Research
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• v.10 no.6
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• pp.318-324
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• 2002

In this paper we have extensively studied what and how processing parameters for quasi-carbonization influence the breaking strength and modulus of resulting quasi-carbon fabrics that are prepared from stabilized PAN fabrics with a spun yarn texture. Seven processing parameters have been considered as follows: applied tension, final heat-treatment temperature, heating rate, heating step, holding time, cooling rate, and purging gas purity. The results indicate that optimal uses of applied tension, final heat-treatment temperature, heating rate, and heating step during quasi-carbonization process are primarily important to increase the tensile properties of quasi-carbon fabrics and holding time, cooling rate, and purging gas purity are less importantly contributed.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.1
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• pp.46-53
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• 1998

The variation of the mechanical properties, microstructures and the formation of retained austenite with heat treatment conditions in austempered ductile cast iron has been investigated. In the case of austempered ductile cast iron below 25mm diameter, it has been found that a pearlite structure are not obtained under a super cooled condition at range of $0.05^{\circ}C/sec{\sim}10^{\circ}C/sec$, and the matrix is precipitated in graphite, bainite and retained austenite. After austempering treatment the retained austenite is increased with decreasing cooling rate. The elongation increases with decreasing super cooling rate, and the optimum result has been shown to be the elongation of 15.6% at super cooling rate of $0.05^{\circ}C/sec$. The optimum result has been shown to be the tensile strength-elongation balance of $1656kgf/mm^2.%$ and it is more than doubled to as the casting state and continuous cooling condition.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.773-779
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• 2005

Properties of Ni-base superalloys of Nimonic 80A alloy system were investigated by the observation of microstructures, precipitates ana hardness as a function of the chemical compositions ana the paths of heat treatment. The higher hardness values showed, the higher Ti/Al ratio among high compositions of Cr and Co element. The lower (Ti+Al) and Fe contents decreased in the same Ti/Al ratio, the higher hardness values showed. This results are considered that coherent deformation was increased with increasing Ti/Al ratio. Hardness showed higher value when Cr contents was $18 wt\%$ less than $21wt\%Cr$. In $3.15 wt\%$Co alloy, $\gamma'$ phase was very fine as around 50nm and, its volume fraction and hardness showed the highest value by 2step-aging treatment.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.11
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• pp.1559-1567
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• 2012

The objective of this study was to evaluate ruminal degradability and intestinal digestibility of crude protein (CP) and amino acids (AA) in hempseed cake (HC) that were moist heat treated at different temperatures. Samples of cold-pressed HC were autoclaved for 30 min at 110, 120 or $130^{\circ}C$, and a sample of untreated HC was used as the control. Ruminal degradability of CP was estimated, using the in situ Dacron bag technique; intestinal CP digestibility was estimated for the 16 h in situ residue using a three-step in vitro procedure. AA content was determined for the HC samples (heat treated and untreated) of the intact feed, the 16 h in situ residue and the residue after the three-step procedure. There was a linear increase in RUP (p = 0.001) and intestinal digestibility of RUP (p = 0.003) with increasing temperature during heat treatment. The $130^{\circ}C$ treatment increased RUP from 259 to 629 g/kg CP, while intestinal digestibility increased from 176 to 730 g/kg RUP, compared to the control. Hence, the intestinal available dietary CP increased more than eight times. Increasing temperatures during heat treatment resulted in linear decreases in ruminal degradability of total AA (p = 0.006) and individual AA (p<0.05) and an increase in intestinal digestibility that could be explained both by a linear and a quadratic model for total AA and most individual AA (p<0.05). The $130^{\circ}C$ treatment decreased ruminal degradability of total AA from 837 to 471 g/kg, while intestinal digestibility increased from 267 to 813 g/kg of rumen undegradable AA, compared with the control. There were differences between ruminal AA degradability and between intestinal AA digestibility within all individual HC treatments (p<0.001). It is concluded that moist heat treatment at $130^{\circ}C$ did not overprotect the CP of HC and could be used to shift the site of CP and AA digestion from the rumen to the small intestine. This may increase the value of HC as a protein supplement for ruminants.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.604-611
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• 2000

Glass-ceramics containing a cordierite (2MgO-2Al2O3-5SiO2) as a main crystal phase was prepared from MgO-Al2O3-SiO2 system glass through a controlled 2-step heat treatment for the application to magnetic memory disk substrate for higher storage capacity. Parent glasses prepared with addition of CeO2 as a fulx and TiO2 as a nucleating agent were crystallized by a 2-step heat treatment i.e. nucleation and crystal grwoth. Then the maximum nucleation and crystal growth rates were investigated and several properties such as bending strength, surface hardness and surface roughness were also studied for heat treated glass. As a result, only a $\alpha$-cordierite was precipitated as a main crystal phase for all heat treatment conditions and the maximum nucleation and crystal growth rates were 2.4$\times$109/㎣.hr at 80$0^{\circ}C$ and 0.3${\mu}{\textrm}{m}$/hr at 915$^{\circ}C$ respectively. After being nucleated at 80$0^{\circ}C$ for 5 hours and then crystallized at 915$^{\circ}C$ for 1 hour, the heat treated glass had a crystal volume fraction of 17.6% and crystal size fo 0.3${\mu}{\textrm}{m}$, and showed the optimum properties for the application to magnetic memory disk substrates as follows. ; Bending strength of 192 MPa, Vidkers hardness of 642.1kgf/$\textrm{mm}^2$, and surface roughness of 27$\AA$.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.264-272
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• 1998

The effect of catalytic condition on the properties of SiO2 aerogels has been investigated and then the dri-ed aerogels were partially densified to induce mechanical strength by heat treatment in order to prepare Type-VI silica by Sol-Gel method. Aerogel made by 1-step base process had the highest skeletal density lowest shrinkage and the smallest particle size. But in case of using acid catalyst in both 1st and 2nd step had the lowest skeletal density highest shrinkage and the largest particle size The aerogel synthesized by 1-step base process was most transparent because of its homogeneous microstructure. During heat treatments cracks occurred below 200$^{\circ}C$ for aerogel with the skeletal density lower than 1.9 g/cm3 but the with the higher skeletal density did not cracked up to 800$^{\circ}C$ shrinkage and skeletal density increased as heating temperature increased due to condensation and viscous sintering mechanism.