• Korean Journal of Materials Research
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• v.14 no.10
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• pp.713-718
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• 2004

To study the dynamic strain aging behavior of Zr-0.4Sn-1.5Nb-0.2Fe sample tube for nuclear fuel cladding in the range of pressurized water reactor (PWR) operation temperature, the tensile tests of the tube specimens, which had been finally heat-treated at $470^{\circ}C\;and\;510^{\circ}C$, had been carried out with the strain rate $1.67{\times}10^{-2}/s\;and\;8.33{\times}10^{-5}/s$ at the various temperatures from room temperature to $500^{\circ}C$. It was observed that the elongation of the specimens got shortened as the temperature increased from $200^{\circ}C\;to\;340^{\circ}C$. The specimens that were finally heat-treated at $470^{\circ}C$ showed a plateau more remarkably on the plot of yield strength-temperature than those heat-treated at $510^{\circ}C$. In the range of $310\sim400^{\circ}C$, the strain rate sensitivity of the specimens finally heat-treated at $510^{\circ}C$ was $30.4\%\sim33.7\%$ lower but the work hardening exponent index of the specimens was a little higher than that without dynamic strain aging effect.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.288-292
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• 2002

Ni-base amorphous alloys were manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties were examined. The reduced glass transition temperature and the supercooled liquid region of $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$alloy were 0.621 and 46 K respectively. $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$ alloy was produced in the rod shape 3mm diameter using the Cu-mold die casting. Hardness, compression strength, elongation and elastic modulus of the alloy were 850 DPN, 2.75 GPa, 1.8% and 150 GPa respectively. Moreover, compression strength of 2.75 GPa was the highest value in the amorphous bulk alloy produced up to now.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.293-299
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• 2012

Ultrafine-grained or nanostructured alloys usually lack the strain hardening capability needed to sustain uniform tensile deformation under high stresses. To circumvent this problem, we fabricated the Cu-based composite reinforced with the 3-dimensionally interconnected $Cu_5Zr$ phase using the combined technique of rapid quenching and subsequent hot-rolling. The alloy exhibited a tensile ductility of ~2.5% together with a strength of 1.57 GPa, which exceeds the values of most commercially available Cu-Be alloys. In this study, we elucidated the structural origin of the high strength and tensile ductility of the developed alloy by examining the thermal stability of the $Cu_5Zr$ reinforcing phase and the energy (work) absorption capability of the Cu matrix.

• Journal of Korea Foundry Society
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• v.35 no.4
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• pp.75-79
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• 2015

Commercial Zr-based amorphous alloy was recycled and oxygen was introduced during the recycling process. The oxygen content can have a great effect on the glass forming ability and the mechanical properties of the alloy. Therefore, it was closely examined. The initial oxygen content in the raw material was 1,244 ppm. It was increased to 3,789 ppm in the alloy after ten recycling processes. As the recycling processes were repeated, the oxygen content increased. Specifically, after four recycling processes, it increased sharply as compared to that after three recycling processes. After ten recycling processes, the glass transition temperature (Tg) increased from 613 K to 634 K and the crystallization temperature (Tx) increased from 696 K to 706 K. On the other hand, the super-cooled liquid region (${\Delta}T=Tx-Tg$) decreased slightly from 83 K to 72 K while the reduced glass transition temperature (Trg = Tg/Tm) was 0.63, remaining constant even when the oxygen content was increased. These results indicated that the increased oxygen content deteriorated the glass forming ability. The bending strength as determined in a three-point bending test showed a sharp decrease from 3,055 to 2,062 MPa as the oxygen content was increased from 1,244 ppm to 3,789 ppm; the extension was also decreased from 3.02 to 1.74 mm. These findings meant that the alloy became brittle.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.3
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• pp.185-189
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• 1999

Effects of alloy modification with the $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.4}$ alloy for an electrode use have been investigated. For the alloy composition, a part of Mn was substituted by Co, Cr and Fe. The experimental results showed that Co accelerated activation of alloy, and Fe and Cr improved the discharge capacity. These results agree with P-C-T curves of each alloy. But substituting Fe for Mn showed the decrease of the discharge capacity when discharged at high rate (60mA, about 1C rate). Considering both the discharge capacity and the high rate discharge property, $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.3}Cr_{0.1}$ alloy was found to be the best alloy among the alloys subjected to the test.

• Transactions of the Korean hydrogen and new energy society
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• v.7 no.1
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• pp.11-18
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• 1996

The Laves phase alloy hydrides have some promising properties as electrode materials in reversible metal hydride batteries. In this work, the hydrogen storage performance, crystallographic parameters, surface morphology, surface area and electrochemical characteristics of the non-stoichiometric $ZrMn_{0.3}V_{0.7}Ni_{1.4+{\alpha}}$, $ZrMn_{0.5}V_{0.5}Ni_{1.4+{\alpha}}$($\alpha$ =0.0, 0.2, 0.4, 0.6) alloys were examined. These as-cast alloys were found to have mainly a cubic C15-type Laves phase structure by X -ray diffraction analysis. The equilibrium pressure of the alloy were increased as $\alpha$ increased in both two types alloy. In case of $ZrMn_{0.5}V_{0.5}Ni_{1.4+{\alpha}}$ alloys, discharge efficiency and the rate capability of the alloy were decreased as $\alpha$ increased but, these values were increased in case of $ZrMn_{0.3}V_{0.7}Ni_{1.4+{\alpha}}$ alloys. The differences of these electrode properties observed were dependent on the reaction surface area and the catalytic activity of unit area of the each electrode.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.2
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• pp.79-90
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• 1997

Extensive work has been done on investigating the inner cell pressure characteristics of sealed type Ni-MH battery in which Zr-Ti-Mn-V-Ni alloy is used as anode. The inner cell pressure of this type Ni-MH battery much more increases with the charge/discharge cycling than that of the other type Ni-MH battery where commercialized $AB_5$ type alloy is used as anode. The increase of inner cell pressure in the sealed type Ni/MH battery using Zr-Ti-Mn-V-Ni alloy system is mainly due to the accumulation of oxygen gas during charge/discharge cycling. The accumulation of oxygen gas arises mainly due to the low rate of oxygen recombination on the MH electrode surface during charge/discharge cycling. The difference of oxygen recombination rate between $AB_5$ type electrode and Zr-Ti-Mn-V-Ni electrode is caused by the difference of electrode reaction surface area resulting from different particle size after their activation and the difference of surface catalytic activity for oxygen recombination reaction, respectively. After EIS analysis, it is identified that the surface catalytic activity affects much more dominantly on the oxygen recombination reaction than the reaction surface area does. In order to suppress the inner cell pressure of Ni-MH battery where Zr-Ti-Mn-V-Ni is used as anode, it is suggested that the surface catalytic activity for oxygen recombination should be improved.

• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.94-99
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• 2010

When the returned scrap of bulk amorphous alloy is remelted, impurities such as oxides and intermetallic compounds increase. Glass forming ability of its scrap is deteriorated remarkably. Melt fluxing technique is introduced to enhance the glass forming ability during melting and freezing of bulk amorphous alloys. Cu and Zr based alloys are chosen. Small pieces of these alloy scraps and $B_2O_3$ flux are put together in a quartz tube. Cyclic heating and cooling are done by induction heating and water quenching or air cooling. Melting fluxing was effective for both Cu-based and Zr-based alloy, and their glass forming abilities were improved with increasing the number of fluxing.

• Transactions of the Korean hydrogen and new energy society
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• v.2 no.1
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• pp.39-46
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• 1990

In order to improve the power of hydride heat pump, prototype heat pump was constructed using $Zr_{0.95}Ti_{0.05}Cr_{0.9}Fe_{1.1}$-$Zr_{0.9}Ti_{0.1}Cr_{0.6}Fe_{1.4}$ which had very good hydrogenation properties. The power changed with operating parameter such as cycle time, air flow rate, and temperature of hot air was investigated. The power shows maximum value with cycle time. The power increased with air flow rate and temperature of hot air. The power of the heat pump was $65-72 Kcal/Kg-alloy{\cdot}h$ under optimum operating condition, which was superior to that the system using $LaNi_{0.9}Al_{0.3}-MmNi_{4.15}Al_{0.66}Fe_{0.2}$ alloy pairs.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.3
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• pp.1-6
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• 1991

In this study, intermediate thermo-mechanical treated Al-2.0 wt%Li, and Al-2.0 wt%Li-1.2 wt%Cu-1.0 wt%Mg-0.12 wt%Zr alloys were tested in tension at $10^{\circ}C$ and elevated temperature(100, 200 and $300^{\circ}C$). The results are follows : The tensile strength of Al-Li-Cu-Mg-Zr alloy is the highest but the elongation of Al-Li alloy is the highest(106%) among the all alloys in tension at $300^{\circ}C$. The Portervin-LeChartlier effect is showed in AI-Li-Cu-Mg-Zr alloy at 10 and $100^{\circ}C$, because of tangled dislocation by Mg and Cu. In the true stress-strain curves of all alloy, the peaks of stress at $300^{\circ}C$ are showed at the strain less than 0.1. In the binary alloy, the dynamic restoration process at 200 and $300^{\circ}C$ is nearly similar to dynamic recovery type. The hot deformation stress is decreased with increase of dynamic recovery degree, but the elongation is increased. When the strain the strain rate are constant, the temperature dependence of hot deformation stress is increased with increase of deformation temperature. The elongation and degree of dynamic recovery are decreased with increase of hot deformation activation energy, but the deformation stresses slightly increased.