• Journal of Powder Materials
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• v.30 no.6
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• pp.484-492
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• 2023

In this study, Ni-Y₂O₃ powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y₂O₃ powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y₂O₃ crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y₂O₃ nanoparticles, and the MA powder formed small Y₂O₃ crystals on the surface of large Ni particles by milling the mixture of Ni and Y₂O₃. The average grain size of Y₂O₃ in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y₂O₃ particles and Ni grains.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.3
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• pp.115-120
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• 2014

Microstructural features were comparatively investigated in AZ91 (Mg-9%Al-1%Zn) and AZ91-0.5%Sn alloys, in order to clarify the reason for the enhancement in room temperature tensile properties by the addition of small amount of Sn in Mg-Al-based alloy. In as-cast state, the Sn-containing alloy showed increased YS, UTS and elongation than the Sn-free alloy. The microstructural examination revealed that various factors including finer cell size, reduction of lamellar (${\alpha}+{\beta}$) phase and morphological change of bulky ${\beta}$ phase from partially divorced shape to fully divorced shape, are likely to be responsible for the improvement in tensile properties for the Sn-containing alloy. It is noted that two alloys showed similar tensile properties after solution treatment. This implies that microstructural evolution related to the ${\beta}$ phase plays a key role in better tensile properties in the Sn-containing alloy.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.207-213
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• 2019

Corrosion and mechanical behavior of the hot-rolled 0.5%Gd-0.8%B-stainless steel to develop a spent nuclear fuel storage material was studied in a simulated nuclear waste treatment condition with rolling condition. The austenite and ferrite phases of the 0.5%Gd-0.8%B-stainless steels are about 88:12. The average austenite and ferrite grain size of the plane normal to rolling, transverse and normal directions of the hot rolled specimens are about 5.08, 8.94, 19.35, 23.29, 26.00 and 18.11 [${\mu}m$], respectively. The average micro-hardness of the as-cast specimen is 200.4 Hv, whereas, that of the hot-rolled specimen are 220.1, 204.7 and 203.5 [$H_v$] for the plane normal to RD, TD and ND, respectively. The UTS, YS and elongation of the as-cast and the hot-rolled specimen are 699, 484 [MPa], 34.0%, and 654, 432 [MPa] and 33.3%, respectively. The passivity was observed both for the as-cast and the hot rolled specimens in a simulated nuclear waste solution. The corrosion potential and corrosion rate of the as-casted specimens are $-343[mV_{SHE}]$ and $3.26{\times}10^{-7}[A/cm^2]$, whereas, those of the hot rolled specimens with normal to ND, RD and TD are -630, -512 and -620 [$mV_{SHE}$] and $6.12{\times}10^{-7}$, $1.04{\times}10^{-6}$ and $6.92{\times}10^{-7}[A/cm^2]$, respectively. Corrosion tends to occur preferentially Cr and B rich area.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.253-258
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• 2006

This paper aims to measure and evaluates the technical efficiency with two inputs and four outputs with the use of fuzzy DEA(Data Envelopment Analysis) in Korean RCC(Rescue Co-ordination Center)/RSC(Rescue Sub-Center). Especially, this paper included not only the marine accident data which occurred for the analysis in particular but also the possibility data of a potential marine accident by an Environmental Stress value and analyzed the technical efficiency. And in this paper, asymmetrical triangular fuzzy number is presented about inputs/ outputs data and a procedure is suggest for it solution. The basic idea is to transform the fuzzy CCR model into a crisp linear programming problem by applying an alternative ${\alpha}-cut$ approach. Also this paper propose a ranking method for fuzzy RCC/RSC using presented fuzzy DEA approach. The result, when ${\alpha}-cut$ is 0.5, efficiency priority should be in order to YS, BS, MP, TS, JJ, PH, US, IC, SC, DR, GS, TA, WD RCC/RSC. Finally, Inefficiency TA, WD RCC/RSC have to benchmarking with reference sets.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.3
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• pp.207-212
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• 2007

This paper aims to measure and evaluate the technical efficiency with two inputs and four outputs with the use of fuzzy DEA in Korean RCC/RSC. Especially, this paper included not only the marine accident data which occurred for the analysis in particular but also the possibility data of a potential marine accident by an Environmental Stress value and analyzed the technical efficiency. And in this paper, asymmetrical triangular fuzzy number is presented about inputs/ outputs data and a procedure is suggested for it's solution. The basic idea is to transform the fuzzy CCR model into a crisp linear programming problem by applying an alternative ${\alpha}$-cut approach. Also this paper propose a ranking method for fuzzy RCC/RSC using presented fuzzy DEA approach. The result, when ${\alpha}$-cut is 0.5, efficiency priority is found in the order of YS, BS, MP, TY, JJ, PH, US, IC, SC, DH, GS, TA, WD RCC/RSC. Finally, Inefficiency TA, WD RCC/RSC have to benchmarking with reference sets.