• 해양환경안전학회지
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• 제22권1호
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• pp.138-144
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• 2016

티타늄은 표면에 형성되는 보호성 부동태 피막 때문에 일반부식과 해수에서 내식성이 강하지만 염산, 황산, 인산 등의 산에서는 보호성 산화물 피막이 파괴된다고 알려져 있다. 본 연구에서는 Ti에 Al 및 V등을 첨가한 ${\alpha}+{\beta}$계에 대하여 $1066^{\circ}C$와 $966^{\circ}C$에서 5시간 용체화 열처리를 실시하고, 이 시편을 $550^{\circ}C$, $600^{\circ}C$, 및 $650^{\circ}C$에서 각각 1시간, 4시간, 8시간 및 16시간 시효열처리한 후 마이크로비커스 경도를 측정하고, 이 시편을 1N $H_2SO_4$ 용액에서 전기화학적 분극법으로 부식을 계측하였으며, 분극을 마친 시편의 표면을 현미경 조직사진으로 부식상태를 검토하였다. 시험 결과 용체화열처리한 시편이 모재와 시효열처리한 시편보다 높은 내식성을 나타내며. 용체화 온도가 높고 시간이 길어질수록 내식성은 증가하였다.

• 열처리공학회지
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• 제32권6호
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• pp.256-262
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• 2019

The microstructural features and texture development by both hot rolling and hot forging in ${\gamma}-TiAl$ alloy were investigated. In addition, additional heat treatment after hot forging was conducted to recognize change of the microstructure and texture evolution. The obtained microstructural features through dynamic recrystallization after hot deformed ${\gamma}-TiAl$ were quite different because two kinds of formation process were occurred depending on deformation condition. However, analyzed texture tends to be random orientation due to intermediate annealing up to ${\alpha}+{\beta}$ region during the hot deformation process. After additional heat treatment, microstructure transformed into fully lamellar microstructure and randomly oriented texture was also observed due to the same reason as before. Tensile test at room temperature demonstrated that anisotropy of mechanical properties were not appeared and transgranular fracture was occurred between interface of ${\alpha}_2/{\gamma}$. As a result, it could be suggested that microstructural features influenced much more than texture development on mechanical properties at room temperature.

• 한국재료학회지
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• 제9권3호
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• pp.322-326
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• 1999

본 연구는 냉간가공과 열처리를 통해 Cu-26.65Zn-4.05Al-0.31Ti(wt%) 형상기억합금의 결정립을 미세화하기 위한 목적으로 수행하였다. 냉간가공을 위하여는 α-상이 가능한 많이 존재하는 (α+β)-조직을 가져야 하는데, 이는 550℃에서 열처리함으로써 얻었고, 최종두께 1mm로 냉간압연하였다. 총 압연율은 70%와 90%이었다. 냉간압연한 판재를 800℃에서 가열 후 급랭함으로써 형상기억특성을 갖는 상으로 변태시켰으며, 이 대 결정립크기를 측정한 결과, 열간압연한 경우보다 냉간압연과 열처리를 한 경우의 결정립이 월등히 작아졌음을 보여주었다. 냉간압연과 열처리를 한 경우에는 냉간압연 변형율이 큰 경우가 결정립이 더 작아지는 경향을 보였다. 또한 결정립크기가 작아짐에 따라 변태온도가 저하되었으며 오스테나이트상이 더 안정하게 되었음을 확인할 수 있었다. In this study, cold-rolling and appropriate annealing was adopted for the grain refining of Cu-26.65Zn-4. 05Al-0.31Ti(wt%) shape memory alloy. For the cold deformation of this alloy the ducti1e α-phase must be contained. After heat treatment at 550℃ the (α+β)-dual phase with 40vol.% α-phase was obtained which could be rolled at room temperature. This alloy was cold rolled into a final thickness of 1.0mm with total reduction degrees of 70% and 90%. The rolled sheets were betanized at 800℃ for various times, then quenched into ice water. The grain size of co]d rolled samples were 60∼80 ㎛ which is much smaller comparing with the hot-rolled samples. And the 90% rolled sample showed smaller grain size than the case of the 70% rolled one. The small grain size had influence on the phase transformation temperatures and stabilization of the austenitic phases.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.79-80
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• 2013

The purpose of this study was to investigate $2^{nd} $nanotube formed surface observation of the Ti-25Ta-xZr alloys using ATO(anodic titanium oxide) technique. Ti-25Ta-xZr alloy was anodized in 1M $H_3PO_4$ electrolytes containing 0.8 Wt. % NaF at room temperature. After formation of nanotube was achieved out, nanotube was eliminated, and then anodization was carried out repeatedly. The microstructures, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and process of nanotube growth by using ATO method was examined by optical microscopy (OM), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The ${\alpha}$ phase and ${\beta}$ phases were affected to form the second nanotube morphology of Ti-25Ta-xZr alloys.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.803-808
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• 2002

A computer-aided alloy-designing technique to develop the insert metal for transient liquid phase (TLP) bonding was applied to high aluminum Ni-base superalloys. The main procedure of a mathematical programming method was to obtain the optimal chemical composition through rationally compromising the plural objective performances of insert metal by a grid-search which involved data estimation from the limited experimental data using interpolation method. The objective function Z which was introduced as an index of bonding performance of insert metal involved the melting point, hardness (strength), formability of brittle phases and void ratio (bonding defects) in bond layer as the evaluating factors. The contour maps of objective function Z were also obtained applying the interpolation method. The compositions of Ni-3.0%Cr-4.0%B-0.5%Ce (for ${\gamma}$/${\gamma}$/${\beta}$ type alloy) and Ni3.5%Cr-3.5%B-3%Ti (for ${\gamma}$/${\gamma}$ type alloy) which optimized the objective function were determined as insert metal. SEM observations revealed that the microstructure in bond layers using the newly developed insert metals indicated quite sound morphologies without forming microconstituents and voids. The creep rupture properties of both joints were much improved compared to a commercial insert metal of MBF-80 (Ni-15.5%Cr-3.7%B), and were fairly comparable to those of base metals.

• 대한치과보철학회지
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• 제42권6호
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• pp.619-627
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• 2004

Statement of problem. Mechanisms of tissue-implant interaction and the effect of the implant surface on the behavior of cells has not yet been clarified. Purpose. This study was performed to investigate the tissue reaction to the titanium alloy submerged into rat peritoneum in vivo. Materials and methods. Titanium alloys (titanium-13Zirconium-6Niobium) were inserted inside the peritoneal cavity of Sprague Dawley rats. After 3 months, the tissue formed around the inserted titanium alloys were examined with a light-microscope. Tissue reaction around the material was analyzed by confocal microscopy to evaluate their biocompatibility in a living body. Results. In in vivo study, foreign body type multinucleated giant cells were found in the fibrous tissue formed as a reaction to the foreign material (4 in 20 cases), but the inflammatory reaction was very weak. After experiment, the contaminants of biomaterials was removed from living tissue. In confocal microscopy, we observed that the staining of vinculin and actin showed mixed appearance. In a few cases, we found that the staining of vinculin and beta-catenin showed the prominent appearance. Conclusion. We found that titanium-13Zirconium-6Niobium alloy was an excellent biomaterial.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.197-197
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• 2016

Commercially pure titanium (CP Ti) and Ti-6Al-4V alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element, such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}-stabilizer$ and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Manganese(Mn) plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Radio frequency(RF) magnetron sputtering in the various PVD methods has high deposition rates, high-purity films, extremely high adhesion of films, and excellent uniform layers for depositing a wide range of materials, including metals, alloys and ceramics like a hydroxyapatite. The aim of this study is to research the Mn coatings on the micro-pore formed Ti-29Nb-xHf alloys by RF-magnetron sputtering for dental applications. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. Each alloy was anodized in solution containing typically 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate at room temperature. A direct current power source was used for the process of anodization. Anodized alloys was prepared using 270V~300V anodization voltage at room. Mn coatings was produced by RF-magnetron sputtering system. RF power of 100W was applied to the target for 1h at room temperature. The microstructure, phase and composition of Mn coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.

• 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.

• Journal of Korean Dental Science
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• 제10권1호
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• pp.10-21
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• 2017

Purpose: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. Materials and Methods: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at $1,000^{\circ}C$ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Self-organized $TiO_2$ was prepared by electrochemical oxidation of the samples in a $1.0M\;H_3PO_4+0.8wt.%$ NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at $36^{\circ}C{\pm}5^{\circ}C$ using a potentiodynamic polarization test. Result: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. Conclusion: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.152-152
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• 2017

Titanium and its alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element,such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}$-stabilizer and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Silicon (Si) and magnesium (Mg) has a beneficial effect on bone. Si in particular has been found to be essential for normal bone and cartilage growth and development. In vitro studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Therefore, in this study, Si and Mg coatings on the hydroxyapatite film formed Ti-29Nb-xHf alloys by plasma electrolyte oxidation has been investigated using several experimental techniques. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. The electrolyte was Si and Mg ions containing calcium acetate monohydrate + calcium glycerophosphate at room temperature. The microstructure, phase and composition of Si and Mg coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.