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Ti-6Al-2Sn-4Zr-6Mo 합금의 고온압축 변형거동
현용택,이용태,이찬규,Hyun, Yong-Taek,Lee, Yong-Tai,Lee, Chan-Gyu 한국재료학회 2001 한국재료학회지 Vol.11 No.2
Ti-6Al-2Sn-4Zr-6Mo(Ti6246) 합금의 고온 변형거동을 조사하기 위하여 $\alpha$+$\beta$ 영역 및 $\beta$영역의 온도에서 $10^0s^{-1}$에서 $10^{-3}s^{-1}$의 변형속도로 압축시험을 수행하였다. 유동응력은 변형속도가 증가하고 시험 온도가 감소함에 따라 증가하였다 90$0^{\circ}C$ 이하에서 시험한 결과로부터 얻어진 유동곡선은 가공연화 현상을 나타내었으나, 이 합금의$\beta$영역인 95$0^{\circ}C$ 이상에서는 유동응력이 지속적으로 증가하다가 정상 상태를 나타냈다. 압축시험 결과로부터 얻은 유동곡선 분석을 통하여 유동응력의 변형량, 변형속도 및 온도에 대한 관계로부터 이 합금에 대한 구성방정식을 구하였다. The hot deformation behavior of Ti-6Al-2Sn-4Zr-6Mo(Ti6246) alloy was investigated in both the $\alpha$+$\beta$ and $\beta$-phase fields by conducting compression tests over a strain rate range of $10^{-3}s^{-1}$ to $10^0s^{-1}$. The flow stress was increased with increasing strain rate and decreasing test temperature. The flow curves obtained at temperatures below 90$0^{\circ}C$ exhibited a flow softening. However, in the $\beta$-phase field, above 95$0^{\circ}C$, the flow stress increased monotonically with plastic strain approaching steady state values. Constitutive equations for the dependence of flow stress on strain, strain rate, and temperature were developed through the analysis of the flow curves.
Hydroxyapatite/poly ε-caprolactone 다공성 지지체의 제조 및 평가
현용택 ( Yong Taek Hyun ),김승언 ( Seung Eon Kim ),허수진 ( Su Jin Heo ),신정욱 ( Jung Woog Shin ),이향미 ( Hyang Mi Lee ),윤석영 ( Seog Young Yoon ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.6
Porous and bioactive composite scaffolds were successfully fabricated by salt leaching method using poly ε-caprolactone (PCL) and hydroxyapatite (HA). The scaffolds have interconnected pore structure with pore size ranging from 200 to 230 ㎛. The pore size of pure PCL scaffolds and PCL/HA scaffolds was similar to that of the salt particles (200-300 ㎛). However, the porosity and the pore size of the PCL/HA composite scaffolds slightly decreased as the HA concentration increased. In addition, the pore walls became thick and the small pores decreased, and consequently the interconnectivity of the pores decreased. The cell viability and response of the scaffolds were assessed by MTT assay. The biological assessment results showed that HA content did not affect initial cell attachment in both scaffolds with and without HA. The osteoblasts proliferated in both types of the scaffolds, but the cell number was higher in the PCL/HA composite scaffolds. It was clearly demonstrated that the incorporation of hydroxyapatite enhances bone cell proliferation rather than initial cell attachment in PCL/HA composite scaffolds. Combining HA and biodegradable polymer could be applicable to bone scaffolding materials.
Ti-Al-Fe계 합금의 고온산화거동에 미치는 Fe의 영향
윤장원,현용택,김정한,염종택,윤석영,Yoon, Jang-Won,Hyun, Yong-Taek,Kim, Jeoung-Han,Yeom, Jong-Taek,Yoon, Seog-Young 한국재료학회 2011 한국재료학회지 Vol.21 No.7
In this paper, high temperature oxidation behavior of newly developed alloys, Ti-6Al-4Fe and Ti-6Al-1Fe, is examined. To understand the effect of Fe on the air oxidation behavior of the Ti-Al-Fe alloy system, thermal oxidation tests are carried out at $700^{\circ}C$ and $800^{\circ}C$ for 96 hours. Ti-6Al-4V alloy is also prepared and tested under the same conditions for comparison with the developed alloys. The oxidation resistance of the Ti-Al-Fe alloy system is superior to that of Ti-6Al-4V alloy. Ti-6Al-4V shows the worst oxidation resistance for all test conditions. This is not a result of the addition of Fe, but rather it is due to the elimination of V, which has deleterious effects on high temperature oxidation. The oxidation of the Ti-Al-Fe alloy system follows the parabolic rate law. At $700^{\circ}C$, Fe addition does not have a noticeable influence on the amount of weight gain of all specimens. However, at $800^{\circ}C$, Ti-6Al-4Fe alloy shows remarkable degradation compared to Ti-6Al-1Fe and Ti-6Al. It is discovered that the formation of $Al_2O_3$, a diffusion resistance layer, is remarkably hindered by a relative decrease of the ${\alpha}$ volume fraction. This is because Fe addition increases the volume fraction of ${\beta}$ phase within the Ti-6Al-xFe alloy system. Activities of Al, Ti, and Fe with respect to the formation of oxide layers are calculated and analyzed to explore the oxidation mechanism.
Ti-10wt.%Al-xMn 분말합금의 Mn첨가에 따른 소결특성 평가
신기승,현용택,박노광,박용호,이동근,Shin, Gi-Seung,Hyun, Yong-Taek,Park, Nho-Kwang,Park, Yong-Ho,Lee, Dong-Geun 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.3
Titanium alloys have high specific strength, excellent corrosion and wear resistance, as well as high heat-resistant strength compared to conventional steel materials. As intermetallic compounds based on Ti, TiAl alloys are becoming increasingly popular in the aerospace field because these alloys have low density and high creep properties. In spite of those advantages, the low ductility at room temperature and difficult machining performance of TiAl and $Ti_3Al$ materials has limited their potential applications. Titanium powder can be used in such cases for weight and cost reduction. Herein, pre-forms of Ti-Al-xMn powder alloys are fabricated by compression forming. In this process, Ti powder is added to Al and Mn powders and compressed, and the resulting mixture is subjected to various sintering temperature and holding times. The density of the powder-sintered specimens is measured and evaluated by correlation with phase formation, Mn addition, Kirkendall void, etc. Strong Al-Mn reactions can restrain Kirkendall void formation in Ti-Al-xMn powder alloys and result in increased density of the powder alloys. The effect of Al-Mn reactions and microstructural changes as well as Mn addition on the high-temperature compression properties are also analyzed for the Ti-Al-xMn powder alloys.
NaCl을 Space holder로 이용한 타이타늄 다공체의 특성
손병휘,홍재근,현용택,김승언,배석천,Son, Byoung-Hwi,Hong, Jae-Geun,Hyun, Yong-Taek,Kim, Seung-Eon,Bae, Seok-Choun 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.6
This study was performed to fabricate the porous titanium foam by space holder method using NaCl powder, and to evaluate the effect of NaCl volume fractions (33.3~66.6 vol.%) on the porosities, compressive strength, Young's modulus and permeability. For controlling pore size, CP titanium and NaCl particles were sieved to different size range of 70~150 ${\mu}m$ and 300~425 ${\mu}m$ respectively. NaCl of green Ti compact was removed in water followed by sintered at $1200^{\circ}C$ for 2 hours. Total porosities of titanium foam were in the range of 38-70%. Pore shape was a regular hexahedron similar that of NaCl shape. Porous Ti body showed that Young's modulus and compressive strength were in the range of 0.6-6 GPa and 8-127 MPa respectively. It showed that pore size and mechanical properties of Ti foams was controllable by NaCl size and volume fractions.
NaOH 처리에 따른 다공성 PCL 지지체의 의사체액 환경에서의 아파타이트 형성
이향미,진형호,현용택,박홍채,윤석영,Lee, Hyang-Mi,Jin, Hyeong-Ho,Hyun, Yong-Taek,Park, Hong-Chae,Yoon, Seog-Young 한국재료학회 2007 한국재료학회지 Vol.17 No.11
Porous poly(e-caprolactone) (PCL) scaffolds were fabricated by salt leaching method. The PCL scaffolds were treated with aqueous NaOH for 0h, 2h, 4h, 8h, and 12h at $40^{\circ}C$. The NaOH-treated PCL scaffolds were dipped in $CaCl_2$ and $K_2HPO_4{\cdot}_3H_2O$ solution alternately three times to induce apatite nuclei onto the surface of the scaffolds. The NaOH-treated PCL scaffolds were immersed into SBF solution for 1day to grow the apatite. The apatite formation were investigated as a fuction of NaOH treatment time. The hydrophilicty and surface area of the PCL scaffolds were increased with NaOH-treatment time. The NaOH-treated PCL scaffolds were successfully formed a dense and uniform bone-like apatite layer after immersion for 1 day in SBF solution.
마이크로파에 의해 합성된 β-TCP/PLGA 복합체의 의사체액에서의 분해 거동
진형호,민상호,현용택,박홍채,윤석영,Jin, Hyeong-Ho,Min, Sang-Ho,Hyun, Yong-Taek,Park, Hong-Chae,Yoon, Seog-Young 한국재료학회 2006 한국재료학회지 Vol.16 No.11
The biodegradable $\beta$-tricalcium phosphate ($\beta$-TCP)/poly(lactide-co-glycolide) (PLGA) composites were synthesized by in situ polymerization with microwave energy. The degradation behavior of $\beta$-TCP/PLGA composite was investigated by soaking in simulated body fluid (SBF) for 4 weeks. The molecular weight of the $\beta$-TCP/PLGA composites decreased with soaking time until week 2, whereas the loss rate of molecular weight reduced after week 2. The incubation time was needed for the degradation of the $\beta$-TCP, indicating that the $\beta$-TCP should be detached from the PLGA matrix and then degraded into SBF solution. The studies of mass loss of the composites with the soaking time revealed that the degradation behavior of PLGA would be processed with the transformation from the polymer to the oligomer followed by the degradation. Morphological changes, whisker-like, due to transformation and degradation of polymer in the composites were observed after week 2. On the basis of the results, it found that the degradation behavior of $\beta$-TCP/PLGA composites was influenced by the $\beta$-TCP content in the composites and the degradation rate of the composites could be controlled by the initial molecular weight of PLGA in the composites.