• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.65-71
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• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. The alloys were cast into phosphate bonded $SiO_2$ investment molds using an argon-arc casting machine, and The hardness and microstructures of the castings were investigated in order to reveal their possible use for new dental casting materials and to collect useful data for alloy design. The hardness of the Ti-13%Zr-5%Cu alloy(379Hv) became higher than that of Ti-13%Zr(317Hv) alloy, and the hardness of this alloys became higher than that of CP Ti(247Hv). Increasing in the hardness of the Ti-13%Zr-5%Cu alloy was considered to be solid solution hardening as the Ti-Zr system shows a completely solid solution for both high temperature $\beta$phase and low temperature $\alpha$ phase and also the inclusion of the eutectoid structure($\alpha Ti+Ti_{2}Cu$). No martensitic structures are observed in the specimen made of CP Ti, but Ti-13%Zr and Ti-13%Zr-5%Cu alloys show a kind of martensitic structure. Ti-13%Zr-5%Cu shows the finest microstructure. From these results, it was concluded that new alloys for dental casting materials should be designed as Ti-Zr-Cu based alloys.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.422-429
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• 2000

To investigate the effect of annealing temperature and time on the recrystallization behavior and microstructure of Zr-based alloys, the specimens of Zr-0.8Sn-0.4Nb-0.4Fe-0.2Cu, Zr-1Nb, Zircaloy-4, and unalloyed Zr were cold-worked and annealed at 400, 500, 600, 700, 800, $900^{\circ}C$ for 30 to 5000 minutes. The hardness, microstructure and precipitate of the specimens were investigated by using micro-hardness tester, optical microscope and transmission electron microscope, respectively. The recrystallization of Zr-based alloys occurred between $400^{\circ}C$ and $600^{\circ}C$. As the content of alloying elements increased, the hardness and recrystallization temperature of the alloys increased though the grain sizes after recrystallization decreased. It was supposed that the hardness of Zr-based alloy with Fe or Cu increased during recovery by the formation of Fe or Cu precipitates.

• Applied Microscopy
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• v.46 no.1
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• pp.32-36
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• 2016

The Cu-based bulk glassy alloys in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The Cu-based bulk glassy alloys samples were tested by X-ray diffractomer (XRD), differential scanning calorimeter, scanning electron microscopy (SEM), Instron testing machine and Vickers hardness instruments. The result indicated that the prepared Cu-Zr-Ti-Ni alloys were bulk glassy alloys. The temperature interval of supercooled liquid region (${\Delta}T_x$) was about 45.48 to 70.98 K for the Cu-Zr-Ti-Ni alloy. The Vickers hardness was up to 565 HV for the $Cu_{50}Zr_{25}Ti_{15}Ni_{10}$ bulk glassy alloy. The $Cu_{50}Zr_{25}Ti_{15}Ni_{10}$ bulk glassy alloys were annealed in order to obtain nanocrystals. The results showed that the Vickers hardness was raise up to 630 HV from 565 HV. As shown in XRD results, the amorphous alloys changed to nanocrystals, which were $Cu_8Zr_3$, $Cu_3Ti_2$ and CuZr, improved the hardness. The SEM analysis showed that the compression fractured morphology of amorphous alloys was brittle fracture, and the fracture morphology after annealing was ductile fracture. This proved that annealing of amorphous to nanocrystals can improve the plasticity and toughness of amorphous alloys.

• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.81-87
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• 2003

Ti-20%Zr-X%Cr(X=0,5) based alloys not containing hamful Al and V were newly designed in order to reveal their possibility for dental casting alloys, and melted in argon-arc casting machine. The mechanical properties were evaluated by using universal testing machine. The tensile strength and %elongaton of the alloys markedly increased with Cr content. The Ti-20%Zr-5%Cr alloy showed a similar tendency with Ti-6%Al-4%V alloy in tensile strength, but surpassed in %elongation. From these results, it was concluded that new alloys for successful dental casting materials should be designed as Ti-Zr-Cr based alloys.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.483-491
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• 2001

The recovery and recrystallization behavior of cold-rolled Zr-based alloys during isothermal annealing at temperatures from $575^{\circ}C$ to $650^{\circ}C$ was studied by thermoelectric power and Vickers microhardness measurement. The recovery and recrystallization resulted in the increase of TEP doe to the extinction of lattice defect, vacancy, dislocation and stacking fault during isothermal annealing after cold- rolling. The completion of recrystallization could be determined much clearly by TEP behavior than by microhardness change in Zr-based alloys. Especially, the recovery and recrystallization were classified separately by TEP behavior in Zr-0.4Nb-xSn alloys. From the analysis of TEP behavior and microhardness, the addition of Sn caused to form the interaction between stain field and dislocation, which resulted in the delay of recovery in Zr-based alloys. The precipitation due the addition of Nb suppressed the grain growth after recrystallization effectively in Zr-based alloys.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.2
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• pp.182-188
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• 2007

[ $Zr_{50}-Ni_{27}-Nb_{18}-Co_5$ ] amorphous alloys ribbon was prepared by a single-roller melt-spinning technique. In order to improve the hydrogen kinetics Pd-coating were carried out on each side of the amorphous ribbon. Pd prevents oxidation of Zr and catalyses the dissociation of molecular hydrogen to atomic hydrogen. In this work, the hydrogen embrittlement and surface properties on Zr-based amorphous alloys were investigated. The Zr-based amorphous alloys were characterized by X-ray diffractometry(XRD) and differential scanning calorimetry(DSC). The morphology of surface and roughness was observed by using scanning electron microscopy(SEM) and atomic force microscopy (AFM). A lattice parameter of both Pd and Zr-based amorphous alloy was increased after hydrogen permeation at 473 K. After hydrogen permeation at 473 K, some cracks were observed on the surface of Pd, which was the cause for the hydrogen embrittlement. The crystallization temperature of Zr-based amorphous alloy was decreased due to the permeated hydrogen.

• Journal of Technologic Dentistry
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• v.23 no.1
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• pp.21-30
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• 2001

For biomedical applications. Ti-X%Zr-Y%Pd(X: $10{\sim}20$, Y:0.2 or 0.4) based alloys not containing harmful Al and V were newly designed, and polarization curves for their alloys were measured at $37^{\circ}C$ in 5% HCl solution in order to understand effects of Zr on the corrosion. From the results of anodic polarization behavior, it was found that the corrosion resistance increased with increasing Zr content. The results show their potential to develope Ti-based alloys for biomedical materials. The Ti-20%Zr-0.2%Pd alloy shows excellent corrosion resistance and was superior to those of the Ti. Ti-6%Al-4%V ELI alloy, Co-30%Cr-6%Mo alloy and STS 316L stainless steel.

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.72-75
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• 2000

For the purpose of developing the non-stoichiometric Zr-based Laves phase alloy with higher capacity and better performance for electrochemical application, extensive work has been carried out in KAIST. After careful alloy design of $ZrMn_2-based$ hydrogen storage alloys through varing their stoichiometry while susbstituting or adding some alloying elements, the $Zr-Ti-(Lh-V-Ni)_{2.2},\;Zr-Ti-(Mn-V-Cr-Ni)_{1.8\pm0.1}$ with high capacity and better performance was developed. Consequently the $Zr-Ti-(Mn-V-Ni)_{2.2}$ alloy has a high discharge capacity of 394mAh/g and shows a high rate capability equaling to that of commercialized $AB_5$ type alloys. On the other hand, in order to develop the hydrogen storage alloy with higher discharge capacity, the hypo-stoichiometric $Zr(Mn-V-Ni)_{2-\alpha}$ alloys substituted by Ti are under developing. As the result of competitive roles of Ti and $stocihiometry({\alpha})$, the discharge capacity of $Zr-Ti-(Mn-V-Cr-Ni)_{l.8\pm0.1}$ alloys is about 400mAh/g(410 mAh/g, which shows the highest level of performance in the Zr-based alloy developed. Our sequential endeavor is improving the shortcoming of Zr-based Laves phase alloy for commercialization, i.e., poor activation property and low rate capability, etc. It is therefore believed that the commercialization of Zr-based Laves phase hydrogen storage alloy for Ni-MH rechargeable battery is in near future.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.57-63
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• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. To investigate the surface reaction layers produced by the reaction with mold materials and the influence of the reaction layers on the hardness of castings, A phosphate bonded $SiO_2$ base investment was used as mold material, and microstructure observation and hardness test were performed. The surface reaction layers of Ti-13%Zr and Ti-13%Zr-5%Cu alloys were thinner than that of CP Ti had a clearly multiple structure. A difference of the hardness between surface and inner of the Ti-13%Zr and Ti-13%Zr-5%Cu alloys became less than that of CP Ti. From the results, it was found that the Ti-Zr-(Cu) based alloys were possible to cast with $SiO_2$ base investment without the great changes of mechanical properties of the castings.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1123-1128
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• 1999

To investigate the effect of Sn on the recrystallization of Zr-based alloys. Zr-xSn (x=0.5, 0.8, 1.5, 2.0wt.%) alloys were manufactured to be the sheets through the defined manufacturing procedure. The specimens were annealed at $300^{\circ}C$ to $800^{\circ}C$ for 1 hour. The hardness, microstructure and precipitate of the alloys with the annealing temperature were investigated by using micro- knoop hardness tester, optical microscope(O/M) and transmission electron microscope(TEM), respectively. The cold-worked Zr-xSn alloys showed the typical behavior of the recovery. recrystallization, and grain growth. The recrystallization of Zr-xSn alloys occurred between $500^{\circ}C$ and $700^{\circ}C$. As the Sn content increased. the recrystallization temperature of the cold-worked alloys increased but their grain sizes after recrystallization decreased. It is suggested that the recrystallization of the cold- worked Zr alloys be occurred by the subgrain coalescence and growth mechanism.