• Korean Journal of Materials Research
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• v.26 no.4
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• pp.200-206
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• 2016

This study was carried out to investigate the effect of W substitution on the precipitation behavior of ${\chi}$ and ${\sigma}$ phases in super duplex stainless steel. The ${\chi}$ phase was precipitated at the interface of ferrite / austenite phases and inside the ferrite phase at the initial stage of aging. With an increase in the aging time, the volume fraction of the ${\chi}$ phase increased, and then decreased with the transformation from the ${\chi}$ phase to the ${\sigma}$ phase. The ${\sigma}$ phase was precipitated later than the ${\chi}$ phase, and the volume fraction of x phase increased with the increase in the aging time. The ferrite phase was decomposed into the new austenite (${\gamma}2$) and ${\sigma}$ phases by aging treatment. The decomposition of the ferrite phase into the ${\gamma}2$ and ${\sigma}$ phases was retarded by W substitution for Mo. The volume fraction of the ${\chi}$ phase increased and that of the ${\sigma}$ phase decreased due to W substitution. The ${\chi}$ and ${\sigma}$ phases were intermetallic compounds, which had lower nickel concentration, and higher chromium, molybdenum, and tungsten concentrations. The ${\chi}$ phase has higher molybdenum and tungsten concentrations than those of the ${\sigma}$ phase. The amounts of chromium and nickel in the ${\chi}$ and ${\sigma}$ phases did not change, but these phases have higher concentrations of molybdenum and tungsten due to W substitution for Mo.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.214-219
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• 2000

In this paper the structural dielectric and piezoelectric properties of Pb［(M $g_{1}$2// $W_{1}$2/)$_{x}$-(N $i_{1}$3//N $b_{2}$3/)$_{0.15-x-(Zr_{0.5})}$ $Ti_{0.5}$)$_{0.85}$］ $O_3$ (x=0.0~0.10) ceramic were investigated with the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$. According to the substitution of Pb(M $g_{1}$2//W/1/2/) $O_3$ curie temperatures were slightly decrease due to the decrease of the tetrag-onality of crystal structure and coercive fields were decreased. Up to the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ 3mol%,remnant polarization dielectric constant piezoelectric constant were increased. Dielectric constant and electro-mechanical coupling factor( $k_{p}$, $k_{31}$ ) were appeared the highest value of 2230, 0.64, and 0.38 and piezoelectric constant( $d_{33}$ , $d_{31}$ ) was the largest value of 418, 202($\times$10$^{-12}$ /C/N), respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/N) respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ was 3mol%.s 3mol%.%.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.2
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• pp.209-213
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• 2005

This study was conducted to determine the optimum substitution level of dried leftover food (DLF) in formula feed for Hanwoo (Korean Native Cattle) steers. A total of forty growing steers were assigned to 5 treatments based on substitution level of DLF (at 0, 25, 50, 75 and 100% level of formula feed). The experiment was carried out with growing steers from 6 months of age to 24 months of age. Average daily gain (ADG) was not affected by DLF substitution level up to 75% of formula feed. However ADG decreased at 100% substitution level. Daily feed intakes were similar among treatments but the amount of feed per 1 kg gain increased with increasing substitution level of DLF. Dressing percentage was around 62% in all treatments without any significant differences. Proportion of quality beef higher than grade 1 was the greatest from animals fed 25% substitution level of DLF. Economic efficiency for Hanwoo steer operator was the highest with 50% substitution level of DLF.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.207-214
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• 1997

Strength experimental on mortar which use Quenched Blast-Furnace Slag as aggregate was carried our for a fundamental study of application possibility of Quenched Blast-Furnace Slag as aggregate. It gives the following results. The strength of mortar use Quenched Blast-Furnace Slag is decrease as substitution rate is higher. As W/C rate increase, the strength decrease, but the strength decrease of fine aggregate rate 1:3 is lower than 1:2. The relation with fine aggregate is that the amount of fine aggregate is inversely proportional to strength. Th relation with age is proportional to strength and strength rate of going is lower than general mortar in 28 age the change of strength proportionately with W/C rate is that as W/C rate increases, th strength is drop ; it shows that it has same tendency as general mortar sand or crushed sand, but while W/C rate increase the strength is as high as general mortar. The reason can be assumed that water content per unit needed to Quenched Blast-Furance Slag is more than in case of sand. In addition, the relation with substitution rate is that the strength is the strongest at substitution rate 25% and 50% ; that is , sometimes it is higher than mortar which use sand 100%. In addition, long age strength of mortar which use Quenched Blast-Furnace Slag as aggregate is about to be studied in the last.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.29-37
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• 2004

The effect of the substitution of Tungsten(W) for Molybdenum(Mo) on the creep behaviour of 22Cr-5Ni duplex stainless steel(DSS) has been investigated. Creep tests were carried out at $600^{\circ}C\;and\;650^{\circ}C$. Intermetallic ${\sigma}$ phase is precipitated during creep at $650^{\circ}C$, at which creep rupture time was much lower compared with at $600^{\circ}C$. The substitution of W for Mo in the duplex stainless steel was known to retard the formation of ${\sigma}$ phase. Minimum creep rate and creep rupture time, however, were hardly influenced by the substitution of 2wt.% W. An ultrasonic measurement for the creep specimens has been carried out for the evaluation of creep damage. The sound velocity increases propotionally with the increase of creep rupture time at $600^{\circ}C$ of creep temperature. On the contrary, the sound velocity decreases with the increase of rupture time at $650^{\circ}C$, which can be correlated with the microstructural evolution during creep.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.99-104
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• 2001

Slag product has the possibility as alternative aggregate and sand under the circumstance of natural resource shortage. Copper slag is the by-product produced in process of copper industry. Recycling the slag in construction industry could give positive effects on the environmental preservation. This study presents that the fundamental properties of high strength concrete which used copper slag as alternative sand. Testing factors are concrete's slump, bleeding, air contents and compressive strength. The results of this study are as follows. (1) Mixing of W/C 30%, substitution rate 25% shows the best slump. As substitution rates are going up, concrete slump is uprising and air contents are downsizing. (2) The bleeding of concrete becomes more serious as substitution rates are going up. (3) The best compressive strength of copper slag concrete is achieved in mixing of W/C 30%, substitution rate 25%.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.40-45
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• 1999

This experimental study presents the strength properties of mortar using the blast-furnace slag sand. The mix disign of this study is based on the each three classes of unit water; (250, 275, 300)kg/㎥ and four classes of W/C; (45, 50, 55, 60)% and substitution rate(0, 25, 50, 75, 100)%. It gives following result. As W/C ratio increase, the strength is decrease. In case of mortar using air-cooled blast-furnace slag sand, the 3-days and 7-days compression strength is increase as substitution rate is higher. But in case of the mortar using the quenched blast-furnace slag sand, the compression strength is decrease as substitution rate is higher.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.417-421
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• 2006

In this study, in order to develop low temperature sintering piezoelectric ceramics for LTCC (Low-Temperature Cofired Ceramic) multilayer piezoelectric actuator, PMW-PMN-PZT ceramics using $0.2wt%\; Li_2CO_3$ and $0.25wt%\;CaCO_3$ as sintering aids were investigated according to the varation of PMW substution. Composition ceramics could be sintered at $900^{\circ}C$ by adding sintering aids. As the amount of PMW substitution increased, the crystal structure of PMW-PMN-PZT ceramics moved from tetragonal phase to rhombohedral phase gradually, and MPB(Morphotrophic Phase Boundary) region appeared at 2 mol% PMW substitution. At the sintering temperature of $900^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}r$), piezoelectric constant(d33) and Curie temperature(Tc) of 2 mol% PMW substituted PMW-PMN-PZT ceramics showed the optimal values of $7.88g/cm^3$, 0.58, 1002, 1264, 352 pC/N and $336^{\circ}C$, respectively, for LTCC multilayer piezoelectric actuator application.

• Journal of Applied Biological Chemistry
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• v.62 no.3
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• pp.299-304
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• 2019

Yogurt was prepared with different substitution ratio [10, 20, 30, and 50% (w/w)] of skim milk with enzymatically saccharified Korean rice wine lees powder (eKRWLP) and fermented with commercially available mixed lactic acid bacteria (Bifidobacterium longum, Lactobacillus acidophilus, Streptococcus thermophilus) at $40^{\circ}C$ for 18 h. Fermentation characteristics were evaluated in terms of acid production (pH and titratable acidity) and viable cell counts of lactic acid bacteria. The pH of yogurts decreased with increasing eKRWLP substitution ratio of skim milk. After 12 h fermentation, titratable acidities of eKRWLP substitution and control (yogurt made without eKRWLP) were 0.84~1.04% and 0.93%, respectively. The titratable acidities of yogurts prepared with 10 and 20% substitution ratio increased than that of the control yogurt, but titratable acidities of yogurts of 30 and 50% substitution ratio decreased. After 9 h fermentation, the number of viable lactic acid bacterial cell were increased to 8.18~8.24 log CFU/g in all yogurts. In sensory evaluation, there were similar preference for eKRWLP yogurts prepared with 10 and 20% substitution ratio and the control. When eKRWLP substitution and control yogurts fermented for 9 h were incubated at $4^{\circ}C$, their pHs and titratable acidities were slightly changed but the number of viable lactic acid bacteria were well maintained above $10^7CFU/g$ for 11 days in yogurts prepared with 10 and 20% substitution ratio among eKRWLP substitution yogurts. These results suggest that eKRWLP can be used as substituent of skim milk and the optimum substitution ratio is around 10~20%.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.75-79
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• 2013

This study was carried out to investigate the precipitation behavior of the ${\chi}$ phase and the impact toughness of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The ${\chi}$ phase was precipitated in the early stage of aging, and with the increasing aging time. However, after reaching a maximum value, the number decreased as a result of the gradual transformation of the ${\chi}$ phase into the ${\sigma}$-phase. It was proved that the ${\chi}$ phase was an intermetallic compound, which represented a lower nickel concentration, higher chromium and molybdenum concentrations, and very higher tungsten concentration compared to the matrix phases. It also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. The decomposition of the ferrite phase into the ${\gamma}_2$ and ${\sigma}$ phases was retarded by W substitution for Mo. Thus, the number of ${\chi}$ phases increased. The impact value was decreased by the substitution of W for Mo. The impact toughness rapidly decreased with time when the ${\chi}$ phase began to precipitate in the initial stage of aging. The impact toughness was, therefore, greatly influenced for the precipitation of the ${\chi}$ phase.