• 대한치과기공학회지
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• 제27권1호
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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.

• 한국재료학회지
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• 제10권6호
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• pp.422-429
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• 2000

Zr 합금의 재결정 거동 및 미세조직 변화에 미치는 열처리 온도 및 시간의 영향의 조사하기위하여 순수 Zr과 Zircaloy-4, Zr-0.88n-0.4Nb-0.4Fe-0.2Cu, Zr-1Nb 합금을 냉간가공한 후 $400^{\circ}C$~$900^{\circ}C$에서 각각 30분~5000분 동안 열처리하였다. 열처리 온도에 따른 Zr합금의 경도, 미세조직 및 석출물 특성을 미소경도기, 광학 현미경 및 투과 전자 현미경을 이용하여 조사하였다. 냉간 가공채는 $400^{\circ}C$에서 $600^{\circ}C$ 범위에서 재결정이 일어났는 데 합금원소가 증가함에 따라 재결정온도가 상승했고 결정립 성장이 억제되었다. 그리고 합금원소 증가에 따른 경도증가 영향이 재결정 이후에도 지속되었다. 열처리 온도 및 시간에 비례하여 재결정 이후 결정립 크기는 증가한 반면 경도변화는 상대적으로 미미하였다. Fe나 Cu가 Zr에 첨가될 경우 회복중 경도증가가 수반되는데, 이는 회복중 생성과 관련이 있는 것으로 사료된다.

• Applied Microscopy
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• 제46권1호
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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.

• 대한치과기공학회지
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• 제25권1호
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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.

• 한국재료학회지
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• 제11권6호
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• pp.483-491
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• 2001

냉간가공된 Zr 합금을 $575^{\circ}C$에서 $650^{\circ}C$의 온도범위에서 유지시간을 달리하여 열처리하는 동안에 발생하는 회복 및 재결정 거동을 TEP(ThermoElectric Power)와 미소경도 분석을 통하여 연구하였다. 냉간가공과 열처리에 따른 합금의 회복 및 재결정온 격자결함, 공공, 전위, 적층결함 등이 소멸함에 따라 TEP가 증가하는 거동을 보였다. 이러한 TEP 분석은 미소경도 분석에 비해 재결정의 완료를 정확하게 예측할 수 있었으며, 특히, Zr-0.4Nb-xSn합금에서는 미소경도 분석으로 쉽게 구분하기 어려운 회복 및 재결정 단계를 명확하게 나타내었다. TBP와 미소경도 분석을 이용한 Zr-base합금의 재결정 거동에 따르면, Sn을 첨가하는 경우에 Sn이 치환형 고용체로 존재하기 때문에 이로 인한 응력장과 전위와의 상호작용에 기인하여 회복이 지연되는 현상을 가져왔으며, Nb함량을 증가시키는 경우에는 재결정 지연 효과가 미미하였으나, 석출물 형성에 의한 결정립 성장의 지연효과가 크게 나타났다.

• 한국수소및신에너지학회논문집
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• 제18권2호
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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.

• 대한치과기공학회지
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• 제23권1호
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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.

• 전기화학회지
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• 제3권2호
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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.

• 대한치과기공학회지
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• 제27권1호
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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.

• 한국재료학회지
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• 제9권11호
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• pp.1123-1128
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• 1999

Zr합금의 재결정에 미치는 Sn 영향을 조사하기 위해서 Zr-xSn (x=0.5, 0.8, 1.5, 2.0wt.%) 합금을 판재로 제조하여 $300^{\circ}C-800^{\circ}C$에서 1시간 동안 열처리하였다. 열처리 온도에 따른 Zr합금의 경도, 미세조직 및 석출물 특성을 미소경도계, 광학 현미경 및 투과 전자 현미경을 이용하여 조사하였다. 냉간가공된 Zr-xSn 합금은 회복, 재결정, 결정립 성장의 전형적인 거동을 나타냈으며, 냉간가공재의 재결정은 $500^{\circ}C$에서 $700^{\circ}C$ 범위에서 완료되었다. Sn량이 증가함에 따라서 합금의 재결정온도는 증가하였고 재결정후의 결정립 크기는 감소하였다. 경도 변화는 미세조직 변화와 잘 일치하는 경향을 보였다. 실험 결과로부터 냉간 가공된 Zr합금의 재결정은 아결정립의 합체 및 성장기구에 의해서 일어나는 것으로 평가되었다.