• 비파괴검사학회지
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• 제20권5호
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• pp.438-444
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• 2000

WC-Co 초경합금의 항자력과 자기포화도를 평가하여 합금조직과 이에 따른 기계적 성질의 예측에 관해 연구하였다. WC 입경이 다르고 탄소함량 및 소결온도가 다른 WC-8%-Co 초경합금을 분말 야금법에 의해 제조하였다. 항자력과 자기포화도와 같은 WC-Co 합금의 자기적 특성은 합금조성 및 조직에 크게 의존하였다. 미소한 합금탄소량의 변화와 WC 입도의 차이에 의해서도 WC-Co 합금의 자기적 특성과 경도 및 항절력이 크게 변화하였다. WC 입도가 미세할수록 소결합금의 항자력과 경도는 증가하였고, 항자력은 경도의 증가와 비례하였다. WC-8%Co 합금의 화학 양론적 조성 아래로 카본함량이 감소하면 자기포화도와 항절력이 떨어지고 $\eta$상의 체적률도 꾸준히 증가하였다. WC-Co 합금에 있어서 자기포화도는 항자력과 반비례하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.928-929
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• 2006

Tensile stress-strain and dynamic acoustic resonance tests were performed on Fe-C-Ni-Cu-Mo high-strength steels, characterized by a heterogeneous matrix microstructure and the prevalence of open porosity. All materials display the first yielding phenomenon and, successively, a continuous yielding behavior. This flow behavior can be described by the Ludwigson equation and developes through three stages: the onset of localized plastic deformation at the pore edges; the evolution of plastic deformation at the pore necks (where the austenitic Ni-rich phase is predominant); the spreading of plastic deformation in the interior of the matrix. The analytical modeling of the strain hardening behavior made it possible to obtain the boundaries between the different deformation stages.

• Corrosion Science and Technology
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• 제11권5호
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• pp.191-195
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• 2012

The aim of this study was to investigate effects of hafnium content on the corrosion behavior of Ti alloys in electrolyte containing chloride ion. For this study, Ti-Hf binary alloys contained 10 wt%, 20 wt% and 30 wt% Hf were manufactured in a vacuum arc-melting furnace and subjected to heat treatment for 12h at $1000^{\circ}C$ in an argon atmosphere. The pitting corrosion behavior of the specimens was examined through potentiodynamic and potentiostatic tests in 0.9 wt% NaCl electrolyte at $36.5{\pm}1^{\circ}C$. The corrosion morphology of Ti-xHf alloys was investigated using optical microscopy (OM) and X-ray diffractometer (XRD). From the optical microstructures and XRD results, needle-like martensite ($\alpha$') phases of the Ti-xHf alloys increased with an increase of Hf addition. Corrosion current density $(I_{corr})$ and current density $(I_{300mV})$ in passive region decreased, whereas, corrosion potential increased with Hf content. At the constant potential ($300mV_{SCE}$), current density decreased as time increased.

• 대한금속재료학회지
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• 제46권10호
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• pp.691-699
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• 2008

Electrochemical characteristics of Ti-30Ta-xZr alloys coated with HA/TiN by using magnetron sputtering method were studied. The Ti-30Ta containing Zr(3, 7, 10 and 15wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and coating, and then coated with HA/TiN, respectively, by using DC and RF-magnetron sputtering method. The analyses of coated surface and coated layer were carried out by using optical microscope(OM), field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). The electrochemical characteristics were examined using potentiodynamic (-1,500 mV~ + 2,000 mV) and A.C. impedance spectroscopy(100 kHz ~ 10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The microstructure of homogenized Ti-30Ta-xZr alloys showed needle-like structure. In case of homogenized Ti-30Ta-xZr alloys, a-peak was increased with increasing Zr content. The thickness of TiN and HA coated layer showed 400 nm and 100 nm, respectively. The corrosion resistance of HA/TiN-coated Ti-30Ta-xZr alloys were higher than that of the non-coated Ti-30TaxZr alloys, whic hindicate better protective effect. The polarization resistance($R_p$) value of HA/TiN coated Ti-30Ta-xZr alloys showed $8.40{\times}10^5{\Omega}cm^2$ which was higher than that of non-coated Ti-30Ta-xZr alloys.

• 대한치과기공학회지
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• 제31권3호
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• pp.15-20
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• 2009

The success of the porcelain fused to gold alloy restoration depends not only on the choice of materials but to a larger degree on the technical skills. The porcelain fused to metal(PFM) alloys containing gold are commonly use for dental purposes in dental laboratory. The gold-colored alloys contain primarily gold, platinum, palladium, and silver, with minimum amounts of such metals as tin, iridium, or titanium. The purpose of this study is on the metal-porcelain fusing layer in porcelain fused to high gold alloy Principal results are as follows. The hardness number(Hv) of PFG is respectively $140.2{\pm}12.6$ in as-casted, $164.3{\pm}14.3$ in heat-treated, $186.6{\pm}20.4$ in fired-treated. The formation of the fusing(intermediate) layer caused by components fusing the interface of porcelain and gold alloy. The main components of the fusing(intermediate) layer are Na, Al, Si, K, Zn, Zr and Ce. The intermediate layer formed by the 2nd firing is more larger than the intermediate layer formed by the 1st firing.

• 대한치과보철학회지
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• 제17권1호
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• Corrosion Science and Technology
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• 제8권4호
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• pp.139-142
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• 2009

Recently, quaternary titanium alloys of the system Ti-Nb-Ta-Zr received considerable research interest as potential implant materials because of their excellent mechanical properties and biocompatibility. However, only few reported works were available on the corrosion behavior of such alloys. Hence, in the present work, electrochemical corrosion of Ti-35Nb-5Ta-7Zr alloy, which has been fabricated by arc melting and heat treatment, was studied in 0.9 wt% NaCl at $37\pm1^{\circ}C$, along with biomedical grade Ti-6Al-4V and CP-Ti. The phase and microstructure of the alloys were investigated employing XRD and SEM. The results of electrochemical studies indicated that the corrosion resistance of the quaternary alloy was inferior to that of Ti-6Al-4V and CP Ti.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.710-711
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• 2006

High strength PM aluminium alloys Al-Zn-Mg-Cu (7075 type) were studied by using commercially available powder blends and the sinter-forging technique for component production. Principal areas of focus include the response to PM processing, micro structural assessment and material properties of Aluminium sinter forged products. Green preforms are successfully sintered to near full density by solid-supersolidus liquid phase sintering. Sinter forging method can produce components with net shape and mechanical characteristics of the material have improved greatly. Properties of this new PM Al-alloy were found to be reproducible in an industrial production environment.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 춘계학술대회 논문집
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• pp.112-112
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• 2015

The purposed of this work was to determine nanotube shape variation on the Ti-xNb alloys with alloying elements and applied potentials. Samples were prepared by arc melting, followed by followed by homogenization for 12 hr at $1000^{\circ}C$ in argon atmosphere. This study was evaluated the phase and microstructure of Ti-xNb alloys using an X-ray diffraction (XRD) and optical microscopy (OM). The morphology of the samples was investigated with a field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). The nanotube on the alloy surface was formed in 1 M $H_3PO_4$ with small additions of NaF 0.8 wt.%. All anodization treatments were carried out using a scanning potentiostat (Model 362, EG&G, USA) at constant voltage 30 V for 120 min, respectively. The morphology of the samples was investigated with a field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Surface characteristics of nanotbue formed on Ti-xNb alloys was investigated by potentiodynamic test and potentiostatic in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. It was observed that the changed ${\alpha}$ phase to ${\beta}$ phase with Nb content.

• 한국콘텐츠학회논문지
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• 제10권11호
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• pp.228-234
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• 2010

치과도재용 합금으로 사용되는 합금 중 베릴륨이 함유된 비귀금속 Ni-Cr합금과 베릴륨이 함유되지 않은 비귀금속 Ni-Cr합금 그리고 베릴륨이 함유되지 않은 비귀금속 Co-Cr 합금과 세라믹간의 결합강도와 파절양상 그리고 계면특성을 분석하고자 하였다. 결합강도는 만능시험기를 이용하여 전단력시험을 통하여 전단결합력을 측정하였으며, 전단시험에 의한 파단면을 이용하여 파절양상을 관찰하였다. 그리고 합금-도재간의 계면을 관찰하였다. 전단결합강도 측정 결과, 베릴륨이 포함된 T-3가 41.13(${\pm}5.11$)MPa로 가장 높게 나타났으며, 베릴륨이 포함된 VeraBond(40.72(${\pm}5.98$)MPa), Co-Cr 합금인 Wirobond(38.40(${\pm}9.66$)MPa), 베릴륨이 포함되지 않은 Verabond 2V(32.77(${\pm}4.31$)MPa), Bellabond N(28.63(${\pm}6.39$)MPa), Bellabond plus(24.97(${\pm}6.13$)MPa), Argeloy N.P. Star(22.69(${\pm}3.41$)MPa) 순으로 나타났다. 비귀금속 합금들과 세라믹간의 파절양상은 모든 시편에서 금속표면에 세라믹이 일부 부착된 복합파절(mixed failure) 양상을 보였다.