• Korean Journal of Materials Research
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• v.24 no.11
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• pp.610-616
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• 2014

In this study, we investigated the precipitation behavior of the R-phase precipitated at the initial stage of aging and its effect on the pitting corrosion of 25%Cr-7%Ni-4%Mo super duplex stainless steel. The R-phase in super duplex stainless steel was mainly precipitated at the interface of ferrite/austenite phases and inside of the ferrite phase during the initial stage of aging, and it was transformed into the ${\sigma}$-phase with an increase in aging time. The ferrite phase was decomposed into a new austenite phase and ${\sigma}$-phase. The R phase was an intermetallic compound, which represented a lower Ni and higher Mo than the matrix, and also had a higher Mo and Cr concentration than the ${\sigma}$ phase. With an increasing aging time, the pitting potential $E_p$ was increased slowly by the precipitation of the R-phase, and it was then steeply decreased by the precipitation of the ${\sigma}$-phase. The R-phase was decreased the pitting potential, but its effect was smaller than effect of ${\sigma}$-phase.

• Journal of Computing Science and Engineering
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• v.2 no.2
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• pp.200-219
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• 2008

The effective management of uncertainty is one of the most fundamental problems in medical decision making. According to the literatures review, most medical decision models rely on point estimates for input parameters. However, it is natural that they should be interested in the relationship between changes in those values and subsequent changes in model output. Therefore, the purpose of this study is to identify the ranges of numerical values for which each option will be most efficient with respect to the input parameters. The Nonhomogeneous Poisson Process(NHPP) was used for describing the behavior of aging chronic diseases. Three kind of failure models (linear, exponential, and power law) were considered, and each of these failure models was studied under the assumptions of unknown scale factor and known aging rate, known scale factor and unknown aging rate, and unknown scale factor and unknown aging rate, respectively. In addition, this study illustrated developed method with an analysis of data from a trial of immunotherapy in the treatment of chronic Granulomatous disease. Finally, the proposed design of Bayesian value of information analysis facilitates the effective use of the computing capability of computers and provides a systematic way to integrate the expert's opinions and the sampling information which will furnish decision makers with valuable support for quality medical decision making.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.197-202
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• 2011

This study was carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}-phase$ which precipitated at the initial stage of aging on mechanical properties of 25%Cr-7%Ni-4%Mo-0.2%N super duplex stainless steel. ${\chi}-phase$ was precipitated mainly at the interface of ferrite / austenite phases and inside of the ferrite phase at the initial stage of aging, and it was transformed into ${\sigma}-phase$ with an increase of aging time. The ferrite phase was decomposed into new $austenite({\gamma}_2)phase$ and ${\sigma}-phase$ by aging treatment. The hardness and tensile strength of the initial stage of aging when ${\chi}-phase$ was precipitated did not changed considerably, while elongation rapidly decreased. Accordingly, it is considered that ${\chi}-phase$ didn't affect the hardness and strength significantly, but it affected the elongation.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.70-77
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• 2000

In this paper, the effect of solution and age heat treatment to the corrosion behavior for the Ti-6Al-4V alloy were studied by cyclic polarization methods. Ti-6Al-4V was solution heat treated at $1,066^{\circ}C$ and $966^{\circ}C$ for 5 hours, and followed by age heat treated at $650^{\circ}C$, $600^{\circ}C$ and $550^{\circ}C$ with 1, 2, 4, 8 and 16 hours under vacuum environment. Test solution was 3.5% NaCl with temperature $25^{\circ}C$. The obtained results were as follows: 1. Base metal was exhibited higher electrical charge than that of solution and aged material. With decrease of solution-treatment temperature from 1066 to $966^{\circ}C$, the electrical charge was increased due to softening of micro structure. 2. The corrosion resistance of specimen that solution treated at $966^{\circ}C$ for 5 hours and age heat treated at 650, 660 and $550^{\circ}C$ were increased with increase of aging time to 4, 8 and 16 hours respectively, and then decreased. 3. In case of 316L stainless steel, measured charge and corrosion potential was 0.0627 coulomb and -614 mV respectively. Corrosion resistance of Ti-6Al-4V was higher than that of 316L.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.13 no.2
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• pp.79-84
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• 2007

Purpose: The data was performed to evaluate the effect of conservative treatment in 30 patients aging from 21 to 71 with lumbar back pain. Methods: The effect of conservative treatment was analyzed with use of pain behavior scale, pain self assessment scale by Million Index in according to age, occupation, duration of symptom, symptom. Results: The occupation were desking job 43.4%, standing job 33.3%, house wife 23.3%. Duration of symptoms in over 2-5 months was 40.0%. The pain in below 1 months, classified by duration of symptoms, was reduced from 2.1 to 3.0 in pain behavior scale, 6.0 to 2.2 in pain self assessment scale(p<0.05). The pain in only lumbar back pain, classified by symptoms, was reduced from 2.0 to 3.0 in pain behavior scale, 6.6 to 2.4 in pain self assessment scale(p<0.05). Conclusion: The pain in over 9 months. classified by duration of physical therapy, was increase 2.0 in pain behavior scale, 4.0 in pain self assessment scale (p<0.05).

• 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 Society for Heat Treatment
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• v.22 no.6
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• pp.345-353
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• 2009

The precipitates of $L2_1$-type $Ni_2AlHf$ phase in B2-ordered NiAl system has been observed by using transmission electron microscope (TEM). The hardness of as-quenched NiAl-Hf alloys is high due to the larger strengthening. However, age hardening of this alloy is not main effect to increase hardness compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1$-type $Ni_2AlHf$ precipitates keep a lattice coherency with the NiAl matrix. The orientation relationship between the $Ni_2 AlHf$ precipitate and the NiAl matrix is <100>$_{Ni2AlHf}$//<100>$_{NiAl}$, {001}$_{Ni2AlHf}$//{001}$_{NiAl}$. By aging treatment for long time $Ni_2AlHf$ precipitates lost their coherency and change their morphology to the spherical ones surrounded by misfit dislocations. The orientation relationship between the NiAl matrix and the $Ni_2AlHf$ precipitates, however, has been kept even after longer aging time. The lattice misfit between the $Ni_2AlHf$ precipitate and the NiAl matrix has been calculated by the selected electron diffraction patterns, and the spacings of misfit dislocations is about 4.5% at 1173 K.

• Journal of Korea Foundry Society
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• v.22 no.2
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• pp.89-96
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• 2002

This study examined the effects of adding Zn to Sn-3.5Ag solder on the microstructure changes and behavior of interface reaction of the solder joint with Cu substrate. The solder/Cu joints were examined with microscope to observe the characteristics of microstructure changes and interfacial reaction layer with aging treatment for up to 120 days at $150^{\circ}C$. Results of the microstructure changes showed that the microstructures were coarsened with aging treatment, while adding 1%Zn suppresses coarsening microstructures. The Sn-3.5Ag/Cu had a fast growth rate of the reaction layer in comparison with the Sn-3.5Ag-1Zn at the aging temperature of $150^{\circ}C$. Through the SEM/EDS analysis of solder joint, it was proved that intermetallic layer was $Cu_6Sn_5$ phase and aged specimens showed that intermetallic layer grew in proportion to $t^{1/2}$, and the precipitate of $Ag_3Sn$ occur to both inner layer and interface of layer and solder. In case of Zn-containing composite solder, $Cu_6Sn_5$ phase formed at the side of substrate and Cu-Zn-Sn phase formed at the other side in double layer. It seems that Cu-Zn-Sn phase formed at solder side did a roll of banrier to suppress the growth of the $Cu_6Sn_5$ layer during the aging treatment.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.2
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• pp.74-79
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• 2012

This study has been carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}$ phase precipitation on the impact toughness of 25%Cr-7%Ni-4%Mo super duplex stainless steel. It was proved that the ${\chi}$ phase was a intermetallic compound, which represented the higher chromium and molybdenum concentration than the matrix phases, and also showed the higher molybdenum concentration than the ${\sigma}$ phase. The ${\chi}$ phase was precipitated at the interface between ferrite and austenite or inside the ferrite matrix in the early stage of aging. The number of ${\chi}$ phase precipitates increased with increasing aging time, however, after showing the maximum value, the number was decreased due to the gradual transformation of ${\chi}$ phase into ${\sigma}$-phase. Aging ferrite phase was decomposed by the $r^2$ phase and ${\sigma}$-phase. Impact toughness rapidly decreased with time in the initial stage of aging at ${\chi}$ phase start to precipitate. Thus, the impact toughness was greatly influence for the precipitation of ${\chi}$ phase.

• Korean Journal of Materials Research
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• v.17 no.8
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• pp.420-424
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• 2007

Precipitation behavior has been studied in NiTi-based ordered alloy using transmission electron microscopy. The hardness after solution treatment is high in NiTi alloy suggesting the large contribution of solid solution strengthening in this alloy system. However, the amount of age hardening is not large as compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1-type$ $Ni_2AlTi$ precipitates keep a lattice coherency with the NiTi matrix. By longer periods of aging $Ni_2AlTi$ precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. Misfit dislocations, which are observed on {100} planes of H-precipitates have the Burgers vector of a <100> with a pure edge type. The lattice misfits of $NiTi-Ni_2AlTi$ system is estimated from the spacings of misfit dislocations to be 1.3% at 1273 K. The lattice misfits decrease with increasing aging temperature in this system.