• Proceedings of the KSME Conference
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• 2005.11a
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• pp.128.2-128.2
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• 2005

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.369-374
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• 2002

To investigate the corrosion behavior of Zr-1.0Nb-xSn (x=1.0, 1.5, 2.0 and 2.5wt. %)alloy system, the corrosion tests of Zr-1.0Nb-xSn alloys were carried out in steam at $400^{\circ}C$ for 125 days and in 70ppm LiOH solution at $360^{\circ}C$ for 180 days. The matrix microstructures of the test specimens were analyzed using TEM and the oxide structures on the test specimens were analyzed using XRD. It was found from the analyses that the more Sn content the alloy had, the faster it was corroded and with the increase of Sn content in the alloy the fraction of $t-ZrO_2$ to $m-ZrO_2$ was decreased. It was also found that the alloys having more Sn showed more dislocation density than those having less.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.94-101
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• 2003

The pressure tubes made of cold-worked Zr-2.5Nb alloy are subjected to creep deformation during service period resulting in changes to their geometry such as longitudinal elongation, diameter increase and sagging. To evaluate integrity of them, information on the material creep property of the serviced tubes is essential. As one of the methods with which the creep property is directly measured from the serviced components, small punch(SP) creep testing has been considered as a substitute for the conventional uniaxial creep testing. In this study, applicability of the SP creep testing to Zr-2.5Nb pressure tube alloy was studied particularly by measuring the power law creep constants, A, n. The SP creep test has been successfully applied fur other high temperature materials which have isotropic behavior. Since the Zr-2.5Nb alloy has anisotropic property, applicability of the SP creep testing can be limited. Uniaxial creep tests and small punch creep tests were conducted with Zr-2.5Nb pressure tube alloy along with finite element analyses. Creep constants obtained by each test method are compared. It was argued that the SP creep test result gave results reflecting material properties of both directions. But the equations derived in the previous study for isotropic materials need to be modified. Discussions were made fur future research directions for application of the SP creep testing to Zr-2.5Nb tube alloy.

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.318-327
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• 1998

The deuterium uptake behavior of Zr-2.5Nb pressure tubes in Wolsong Unit 1 was analyzed in terms of longitudinal location, operation time, and coolant temperature. The results were compared with those obtained from Canadian CANDU reactors. The amount of deuterium uptake was higher at the outlet part than at the inlet part and was also higher when subjected to a longer operation time and a higher coolant temperature. The hydrogen uptake of Zr-2.5Nb in a hydrogen gas atmosphere was dependent on the microstructure of the alloy. The aged Zr-2.5Nb consisting of $\alpha$-Zr and $\beta$-Nb phases showed higher hydrogen uptake than that consisting of $\alpha$-Zr and $\beta$-Zr phases. The hydrogen in the alloy decreased the rate of oxidation. This could be explained in terms of the cathodic controlled reaction of Zr-2.5Nb oxidation.

• Korean Journal of Materials Research
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• v.8 no.1
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• pp.3-9
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• 1998

40$0^{\circ}C$ H$_{2}$O, D$_{2}$O및 $O_{2}$분위기에서 Zr-2.5Nb합금의 부식거동을 분석하였다. Martensitic $\alpha$'-Zr상이나 $\alpha$-Zr과 $\beta$-Zr상의 Zr-2.5Nb합금인 경우, 부식분위기에 매우 민감하여, $O_{2}$속에서 가장 큰 부식속도를 보였다. 반면, $\alpha$-Zr나 $\beta$-Zr상의 경우, 부식 매질에 따른 별다른 차이없이 높은 부식저항성을 보였다. 이러한 Zr-2.5Nb 합금의 미세조직 및 부식 매질에 따른 부식거동변화는 Zr-2.5Nb 합금의 음극 지배 부식반응의 관점으로 해석되었으며, 이들 결과를 이용하여 CANDU 형및 RBMK 형 Zr-2.5Nb 압력관의 가동조건 차이를 설명할 수 있었다. Zr-2.5Nb 합금의 모든 조직에서 주로 단사정 ZrO$_{2}$산화물이 형성되었으며, 산화물내 정방정 ZrO$_{2}$비율은 산화물 두께가 증가함에 따라 감소하였다.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.1031-1037
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• 1998

To investigate the effect of cooling rate and annealing temperature on the corrosion of Zircaloy-4 and Zr-2. 5Nb alloys, autoclave corrosion tests were performed at $500^{\circ}C$ for the specimens prepared by various heat treatments. The specimens were heat-treated at $1050^{\circ}C$ for 30 minutes and cooled by ice-brine quenching, water quenching, oil quenching, air cooling, and furnace cooling. To investigate the effect of annealing temperature, the specimens were annealed at $\alpha$, ($\alpha$+$\beta$)-, and $\beta$-temperatures. It was observed from the $500^{\circ}C$ corrosion test that nodular corrosion occurred on the Zircaloy-4 alloy but did not occur on the Zr-2.5Nb alloy. The corrosion resistance of Zircaloy-4 increased with increasing the cooling rate. On the other hand, the corrosion resistance of Zr-2.5Nb decreased with increasing the cooling rate and the annealing temperature. It is suggested that corrosion resistance of Zircaloy-4 would be controlled by the distribution of Fe and Cr element in the matrix and precipitates, while that of Zr-2.5Nb alloy the niobium concentration and $\beta_{-Nb}$ phase.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.378-385
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• 1999

To evaluate the effect of Sn on the corrosion behavior of Zr alloys for nuclear fuel claddings, the corrosion tests on the binary Zr-xSn and the ternary Zr-0.4Nb-xSn alloys were performed in water at $360^{\circ}C$. The binary alloys containing 0.5, 0.8 and 1.5wt.% Sn showed the transition corrosion rate at 15 days. On the other hand, the binary alloy containing 2.0wt.% Sn showed a good corrosion resistance without the transition of corrosion rate up to 80 days. The corrosion rate of the ternary alloy increased with increasing Sn content. The difference of corrosion behaviors between binary and ternary alloys is considered due to the different solubility of Sn, Nb content and precipitates. The corrosions of Zr-xSn and Zr-0.4Nb-xSn alloys would be controlled by the fraction of tetragonal-$ZrO_2$and the amount of hydrogen pick-up.

• Journal of Korea Foundry Society
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• v.18 no.5
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• pp.488-493
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• 1998

Commercially pure titanium(cp-Ti) and Ti-15wt%Zr-4wt%Nb-4wt%Ta alloy were melted in vacuum induction furnace. According to the chemical analysis, the content of carbon was above ASTM standard in the cast ingots because of using graphite crucible. The TEM micostructures of cp-Ti and Ti alloy shows that chemically stable TiC precipitates distribute in ${\alpha}-Ti$ matrix. In order to examine the properties of cp-Ti and Ti-Zr-Nb-Ta alloy for dental applications, mechanical properties and corrosion resistance were investigated. The anodic polarization properties of Ti-Zr-Nb-Zr alloy were almost same as that of cp-Ti in 1% lactic acid. However, as the results of the anodic polarization test in 5% HCl, it was known that Ti-Zr-Nb-Zr alloy showed a rapid decrease in current density at higher potential in comparison with cp-Ti. The yield stress and tensile strengh in Ti-Zr-Nb-Ta were ${\sigma}_{0.2}=623\;MPa$, ${\sigma}_{T.S.}=708\;MPa$ and these results showed 30% increase in yield stress in comparison with cp-Ti.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.217-217
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• 1998

• Journal of Korea Foundry Society
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• v.22 no.5
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• pp.252-256
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• 2002

Ni-Nb-Ti-Zr amorphous alloys were manufactured using melt-spinning methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties were examined. The value of the reduced glass transition temperature and the supercooled liquid region of $Ni_{62}Nb_{10}Ti_{13}Zr_{15}$ alloy were relatively high and were 0.612 and 76 K respectively. However, amorphous bulk alloy rod was not formed using the Cu-mold die casting. The mechanical properties were in the range of $800{\sim}900DPN$ of hardness and $2.5{\sim}2.8$ GPa of tensile strength in the whole composition range.