• Analytical Science and Technology
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• v.9 no.2
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• pp.192-197
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• 1996

The purpose of this study is to develop new V-free Ti alloys which have good mechanical properties and corrosion resistance. Although pure Ti has an excellent biocompatibility and corrosion resistance in body, it is inferior to Ti alloys in mechanical properties, and Ti-6Al-4V which has good mechanical properties was known to be cytotoxic due to the alloying element V. New Ti based alloys which do not contain the toxic metallic components were developed by the alloy design technique. Their corrosion and mechanical characteristics were compared with pure Ti and Ti-6Al-4V in this study. The results showed that Ti-20Zr-3Nb-3Ta-0.2Pd-1In and Ti-5AI-4Zr-2.5Mo exhibit good mechanical oroperties and an excellent corrosion resistance in 0.9% NaCl solution.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.347-354
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• 2001

Compression tests were carried out to investigate the hot-deformation behavior of Ti-6Al-4V alloy in the temperature range of $915^{\circ}C$ to $1015^{\circ}C$ and the strain rate range of $10^{-3}s^{-i}$ to $10s^{-1}$. Under the given test conditions, the hot-deformation of Ti-6Al-4V alloy was mainly led by dynamic recovery rather than by dynamic recrystallization. The activation energy for the plastic deformation in $\alpha+\beta$ field was about 894 kJ/mol and $\beta$ field was 332kJ/mo1. Processing map for hot working are developed on the basis of the variations of efficiency of power dissipation($\eta$=2m/m＋1) and flow instability criterion using the dynamic material model. The optimum process condition in the ($\alpha＋\beta$) field was obtained at the temperature ranges of $930^{\circ}C$ to $955^{\circ}C$$^{\circ}C$ and a strain rate of $10^{-3}s{-1}$.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.2
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• pp.66-74
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• 2016

In this study, characteristics of TiAl alloy and SCM440 (Cr-Mo steel) have been investigated with the various joining condition by servo motor type friction welder. The experimental factors of friction welder used in this study are spindle revolution, friction speed, and distance, upset speed and distance, respectively. Servo motor type friction welder could be controlled by the level of oil pressure, and it could be performed by position control dependence of electrical energy. Mechanical properties and morphology of welded interface were characterized by various joining condition. This aroused due to the bond strength dependence on friction heat and size of the heat affected zone. Therefore, it is necessary to have enough friction heat and decreased heat affected zone for good friction welding between dissimilar metals. An optimum bond was obtained between TiAl alloy and SCM440 by controlling friction speed and distance. At the spindle revolution 4,000 rpm, friction speed 120 mm/min, friction distance 15 mm, the bond strength was found to be 312 MPa.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.279-284
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• 2017

Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.4
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• pp.189-202
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• 2000

$AB_2$ type Zr-based Laves phases alloys have been studied for potential application as a negative electrode in a Ni-MH battery. The $AB_2$-type electrodes have a much higher energy density than $AB_5$-type electrodes per weight, however they have some disadvantages such as poor activation behavior and cycle life etc. Nonetheless, the $AB_2$-type electrodes have been studied very extensively due to their high energy density. In this study, in order to develop the cycle life, the Mn of $AB_2$ alloy composition was substituted partially by Mo. The alloys were melted by arc furnace and remelted 4-5 times for homogeneity. The alloy powder was used below 200-325 mesh for experiments. The structures and phases of the alloys were analyzed by XRD, SEM and EDS, and measured the curve of a pressure-composition isotherms. The electrodes were prepared by cold pressing of the copper-coated(25 wt%) alloy powders, and tested by a half cell. The results are summarized as follows. The cycle life was improved with the increase of Mo amount in $Zr_{1-x}Ti_xV_{0.4}Ni_{1.2}Mn_{0.4}Mo_y$(x=0.3, 0.4) and the activation was faster, whereas the discharge capacity decreased.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.1
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• pp.51-62
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• 2014

The purpose of this experiment was to evaluate the apatite-formation abilities of low-modulus Ti-7.5Mo substrates treated with NaOH aqueous solutions and subsequent ethyl alcohol aging before soaking them in simulated body fluid. Specimens of Ti-7.5Mo were initially treated with 5 M NaOH at $60^{\circ}C$ for 24 h, resulting in the formation of a porous network structure composed of sodium hydrogen titanate. Afterwards, the specimens were aged in ethyl alcohol at $60^{\circ}C$ for 5 or 10 min, and subsequently immersed in simulated body fluid at $37^{\circ}C$ for 3, 7 and 14 days. Ethyl alcohol aging significantly increased the apatite-forming abilities of Ti-7.5Mo. The amount of apatite deposited on the Ti-7.5Mo after NaOH treatment and subsequent ethyl alcohol aging was much greater, especially after the Ti-7.5Mo specimens were aged for 5 min. Due to its excellent combination of bioactivity, low elastic modulus and low processing costs, the Ti-7.5Mo treated with NaOH aqueous solutions and subsequently aged in ethyl alcohol has promising heavy load-bearing applications.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.21-25
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• 2015

Bending fatigue characteristics of Cu films and $8{\mu}m$ width Cu interconnects on flexible substrates were investigated, and fatigue reliability improvement was achieved through Mo-Ti alloy adhesion layer. Tensile bending fatigue reliability of Cu interconnects is 3 times lower than that of Cu films, and even compressive bending fatigue reliability of Cu interconnects is 6 times lower than that of Cu films. From these results, mechanical crack formation could be fatal in Cu interconnects. With Mo-Ti adhesion layer, fatigue reliability of Cu films and interconnects were enhanced due to the increase of adhesion strength and the suppression of slip induced crack initiation.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.636-641
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• 2015

Titanium has many special characteristics such as specific high strength, low elastic modulus, excellent corrosion and oxidation resistance, etc. Beta titanium alloys, because of their good formability and strength, are used for jet engines, and as turbine blades in the automobile and aerospace industries. Low cost beta titanium alloys were developed to take economic advantage of the use of low-cost beta stabilizers such as Mo, Fe, and Cr. Generally, adding a trace of boron leads to grain refinement in casted titanium alloys due to the pinning effect of the TiB phases. This study analyzed and evaluated the microstructural and mechanical properties after plastic deformation and heat treatment in boron-modified Ti-2Al-9.2Mo-2Fe alloy. The results indicate that a trace of boron addition made grains finer; this refinement effect was found to be maintained after subsequent processes such as hot forging and solution treatment. This can effectively reduce the number of required manufacturing process steps and lead to savings in the overall cost as well as low-cost beta elements.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.05a
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• pp.20.2-20.2
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• 2007

• Journal of Powder Materials
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• v.14 no.4
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• pp.230-237
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• 2007

The fabrication of Fe alloy-40 wt.%TiC composite materials using spark plasma sintering process after ball-milling was studied. Raw powders to fabricate Fe alloy-TiC composite were Fe alloy, $TiH_{2}$ and activated carbon. Fe alloy powder was Distaloy AE (4%Ni-1%Cu-0.5%Mo-0.01%C-bal.%Fe) made by Hoeganes company with better toughness and lower melting point. These powders were ball-milled in horizontal attrition ball mill at a ball-to-powder weight ratio of 30 : 1. After that, these mixture powders were sintered by using spark plasma sintering apparatus for 5 min at $1200-1275^{\circ}C$ in vacuum atmosphere under $10^{-3}$ torr. DistaloyAE-40 wt.%TiC composite was directly synthesized by dehydrogenation and carburization reaction during sintering process. The phase transformation of as-milled powders and sintered materials was confirmed using X-ray diffraction (XRD) and transmission electron microscope (TEM). The density and harness materials was measured in order to confirm the densification behavior. In case of DistaloyAE-40 wt.%TiC composite retained for 5 min at $1275^{\circ}C$, it has the relative density of about 96% through the influence of rapid densification and fine TiC particle reinforced Fe-based composites materials.