• Korean Chemical Engineering Research
• /
• v.54 no.5
• /
• pp.598-605
• /
• 2016

V-Cr-Y alloy is a material for hydrogen separation membrane possessing high transmittance and selectivity. In order to increase the rate of hydrogen permeation flux through the membrane, V-Cr-Y thin film was prepared using a sputtering technique and was investigated focusing on its basic properties. Thin film was deposited on a silicon wafer using a target including V (89.8%), Cr (10.0%) and Y(0.2%), and results of EDS analysis confirm that the ratio of metal in thin film agrees with that in the target. Higher sputtering temperature and power resulted in more rapid growth rate of the thin film and larger size of the crystals, and denser and finer crystal structure was observed when lower pressure was applied. An optimal sputtering condition was found with RF, 2mTorr, 300W and ambient temperature, and a suitable V-Cr-Y thin film for hydrogen separation was obtained upon heat treatment of the thin film prepared in this way.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.611-614
• /
• 2005

In this paper, investigated is the relationship between the formation temperature and the thermal stability of Ni silicide formed with Ni-V (Nickel Vanadium) alloy target. The sheet resistance after the formation of Ni silicide with the Ni-V showed stable characteristic up to RTP temperature of $700\;^{\circ}C$ while degradation of sheet resistance started at that temperature in case of pure-Ni. Moreover, the Ni silicide with Ni-V indicated more thermally stable characteristic after the post-silicidation annealing. It is further found that the thermal robustness of Ni silicide with Ni-V was highly dependent on the formation temperature. With the increased silicidation temperature (around $700\;^{\circ}C$), the more thermally stable Ni silicide was formed than that of low temperature case using the Ni-V.

• Transactions of Materials Processing
• /
• v.29 no.4
• /
• pp.211-217
• /
• 2020

This paper presents a study on the hydrogen embrittlement of Ti-6Al-4V alloys with different microstructures depending on annealing treatment. They were electrochemically charged with hydrogen and subjected to tensile tests to investigate hydrogen embrittlement behavior. Tensile test results showed that the elongation of Ti-6Al-4V alloy specimens was remarkably decreased with increasing the volume fraction of β phase after hydrogen charging. This is because the β phase with a relatively low diffusivity tends to easily form a hydride at grain boundaries during electrochemical hydrogen charging. After hydrogen charging of the Ti-6Al-4V alloy specimen, it found that silver particles were decorated mostly at the grain boundary, and coarser silver particles were usually formed in the specimen annealed at 950 ℃. Therefore, the specimen having higher β phase fraction shows a poor hydrogen embrittlement resistance because the β phase promotes the formation of coarse hydride during electrochemical hydrogen charging, which leads to a large decrease in ductility.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1997.07a
• /
• pp.142-143
• /
• 1997

• Journal of Korea Foundry Society
• /
• v.20 no.2
• /
• pp.104-109
• /
• 2000

Three different white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their abrasion wear behavior in as-cast and heat-treated conditions. The specimens were produced using a 15㎏-capacity high frequency induction furnace. Melts were super-heated to $1600^{\circ}C$, and poured at $1550^{\circ}C$ into Y-block pepset molds. Three combinations of the alloying elements were selected so as to obtain the different types of carbides : 3%C-10%Cr-5%Mo-5%W(alloy No. 1: $M_7C_3$ and $M_6C$), 3%C -10%V-5%Mo-5%W(alloy No. 2: MC and $M_2C$) and 3%C-17%Cr-3%V(alloy No. 3: $M_7C_3$ only). A scratching type abrasion test was carried out in the states of as-cast(AS), homogenizing(AH), air-hardening(AHF) and tempering(AHFT). First of all, the as-cast specimens were homogenized at $950^{\circ}C$ for 5h under the vacuum atmosphere. Then, they were austenitized at $1050^{\circ}C$ for 2h and followed by air-hardening in air. The air-hardened specimens were tempered at $300^{\circ}C$ for 3h. 1 ㎏ load was applied in order to contact the specimen with abrading wheel which was wound by 120 mesh SiC paper. The wear loss of the test piece(dimension: $50{\times}50{\times}5$ mm) was measured after one cycle of wear test and this procedure was repeated up to 8 cycles. In all the specimens, the abrasion wear loss was found to decrease in the order of AH, AS, AHFT and AHF states. Abrasion wear loss was lowest in the alloy No.2 and highest in the alloy No.1 except for the as-cast and homogenized condition in which the alloy No.3 showed the highest abrasion wear loss. The lowest abrasion wear loss of the alloy No.2 could be attributed to the fact that it contained primary and eutectic MC carbides, and eutectic $M_2C$ carbide with extremely high hardness. The matrix of each specimen was fully pearlitic in the as-cast state but it was transformed to martensite, tempered martensite and austenite depending upon the type of heat-treatment. From these results, it becomes clear that MC carbide is a significant phase to improve the abrasion wear resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.04b
• /
• pp.9-12
• /
• 2004

This paper investigated the stability of Ta-Mo alloy on thin gate dielectric. Ta-Mo alloy was deposited by using co-sputtering process after thermal growing of 3.4nm and 4.2nm silicon dioxide. When the sputtering power of Ta and Mo were 100W and 70W, respectively, the suitable work function for NMOS gate electrode, 4.2eV, could obtain. To prove interface thermal stability of thin film gate dielectric and Ta-Mo alloy, rapid thermal annealing was performed at $600^{\circ}C$ and $700^{\circ}C$ for 10sec in Ar ambient. The results of interface reaction were surveyed by change of silicon dioxide thickness and work function after annealing process. Also, the reliability of alloy gate and gate dielectric could be confirmed by quantity of leakage current. Ta-Mo alloy was showed low sheet resistance and thermal stability, namely, little change of gate dielectric and work function, after $700^{\circ}C$ annealing process.

• Journal of the Korean Society for Heat Treatment
• /
• v.16 no.4
• /
• pp.191-196
• /
• 2003

For improvement of the wear performance of Ti alloy, vacuum-carburizing technique was tried for the first time using propane atmosphere. During the low pressure carburizing carbide was formed at the surface and carbon transfer was occurred from the carbide to the matrix. It was found that: (i) surface hardness increased with the reduction of operating pressure and time; (ii) optimum hardness distribution could be obtained with the proper choice of temperature and carbon flux control; and, (iii) case depth was largely influenced not by time but by temperature. The two steps process was recommended for obtaining thick case depth and high surface hardness of Ti alloy. For the low oxygen partial pressure, it was necessary to introduce additional CO gas to the atmosphere.Grain boundary oxidation and non-uniformity could be prevented.

• Transactions of Materials Processing
• /
• v.27 no.3
• /
• pp.139-144
• /
• 2018

Many studies have been conducted on the process of forming magnesium alloy sheets to reduce the body weights of vehicles. Magnesium has a lower specific gravity than steel and also has a higher specific strength. Mg alloy sheets have low formability and a lot of springback due to their limited ductility and low young's modulus. As the temperature increases, the yield strength of the material decreases. Warm forming increases the formability and minimizes the springback of a material by heating it and the die to reduce the required load at forming. In this study, the temperature of the AZ31B sheet was controlled in order to reduce springback and increase formability. However, as the temperature increased, the deformation characteristics of the material changed and the radius of curvature of the material increased. The load and springback amount required for forming were analyzed according to the temperature and the bottoming force in the bending deformation.

• Korean Journal of Metals and Materials
• /
• v.50 no.2
• /
• pp.164-170
• /
• 2012

Nanotubular structure formation on the Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods has been studied using the anodizing method. A nanotube layer was formed on Ti alloys in 1.0 M $H_3PO_4$ electrolyte with small additions of $F^-$ ions. The nanotube nucleation and growth of the ${\alpha}$-phase and ${\beta}$-phase appeared differently, and showed different morphology for Cp-Ti, Ti-6Al-4V and Ti-Ta alloys. In the ${\alpha}$-phase of Cp-Ti and martensite ${\alpha}^{\prime}$ and in the ${\alpha}^{{\prime}{\prime}}$ and ${\beta}$-phase of the Ti-Ta alloy, the nanotube showed a clearly highly ordered $TiO_2$ layer. In the case of the Ti-Ta alloy, the pore size of the nanotube was smaller than that of the Cp-Ti due to the ${\beta}$-stabilizing Ta element. In the case of the Ti-6Al-4V alloy, the ${\alpha}$-phase showed a stable porous structure; the ${\beta}$-phase was dissolved entirely. The nanotube with two-size scale and high order showed itself on Ti-Ta alloys with increasing Ta content.

• Journal of Korea Foundry Society
• /
• v.15 no.3
• /
• pp.235-241
• /
• 1995

In order to improve the production process of low cost and high purity Vanadium, this study was done to reduce $V_2O_5$ into V-Al master alloy by Aluminothermic Reduction, followed by refining of V-Al master alloy electron beam melting. As melting time was increased in electron beam melting of V, the contents of interstitial impurities and Al, Fe were decreased but the contents of Si, Mo and W were increased due to lower vapor pressure of these elements than that of matrix V. Consequently, it was profitable that melting of V was done for 180 seconds. In addition, with number of melting, the purity of V did not significantly vary, because volatile impurities in V were removed mostly during the first step of melting. As a result of V refining by electron beam melting, high purity Vanadium of 3N(99.91wt%) was acquired including interstitial impurities total contents of which were maximum 400ppm.